diff --git a/.changeset/good-glasses-wait.md b/.changeset/good-glasses-wait.md
new file mode 100644
index 0000000..2582e1c
--- /dev/null
+++ b/.changeset/good-glasses-wait.md
@@ -0,0 +1,11 @@
+---
+"@arethetypeswrong/core": minor
+---
+
+Add support for DefinitelyTyped analysis.
+
+- `createPackageFromNpm` now takes an options parameter that can control DefinitelyTyped inclusion.
+- The `Package` type is now a class, with new properties and methods:
+  - `typesPackage` contains the package name and version for the included DefinitelyTyped package, if any.
+  - `mergedWithTypes(typesPackage: Package)` returns a new `Package` instance with all files from both packages and the `typesPackage` instance property metadata filled in.
+- `createPackageFromTarballData` is no longer asynchronous.
diff --git a/.changeset/loud-hairs-relate.md b/.changeset/loud-hairs-relate.md
new file mode 100644
index 0000000..b3c04fc
--- /dev/null
+++ b/.changeset/loud-hairs-relate.md
@@ -0,0 +1,9 @@
+---
+"@arethetypeswrong/cli": minor
+---
+
+Add support for DefinitelyTyped analysis.
+
+- `@types` packages will be fetched by default for implementation packages that do not contain any TypeScript files.
+- `--definitely-typed` can be used to set the version of the `@types` package fetched. By default, the version is inferred from the implementation package version.
+- `--no-definitely-typed` can be used to prevent `@types` package inclusion.
diff --git a/packages/cli/README.md b/packages/cli/README.md
index 5e3a45c..38ec420 100644
--- a/packages/cli/README.md
+++ b/packages/cli/README.md
@@ -75,7 +75,7 @@ attw --pack .
 
 #### From NPM
 
-Specify the name (and, optionally, version range) of a package from the NPM registry instead of a local tarball filename.
+Specify the name (and, optionally, version or SemVer range) of a package from the NPM registry instead of a local tarball filename.
 
 In the CLI: `--from-npm`, `-p`
 
@@ -85,6 +85,17 @@ attw --from-npm <package-name>
 
 In the config file, `fromNpm` can be a boolean value.
 
+#### DefinitelyTyped
+
+When a package does not contain types, specifies the version or SemVer range of the DefinitelyTyped `@types` package to use. Defaults to inferring the best version match from the implementation package version.
+
+In the CLI: `--definitely-typed`, `--no-definitely-typed`
+
+```shell
+attw -p <package-name> --definitely-typed <version>
+attw -p <package-name> --no-definitely-typed
+```
+
 #### Format
 
 The format to print the output in. Defaults to `auto`.
diff --git a/packages/cli/src/index.ts b/packages/cli/src/index.ts
index b2955d7..40c686e 100644
--- a/packages/cli/src/index.ts
+++ b/packages/cli/src/index.ts
@@ -25,6 +25,7 @@ type Format = (typeof formats)[number];
 export interface Opts {
   pack?: boolean;
   fromNpm?: boolean;
+  definitelyTyped?: boolean | string;
   summary?: boolean;
   emoji?: boolean;
   color?: boolean;
@@ -55,6 +56,8 @@ particularly ESM-related module resolution issues.`
   )
   .option("-P, --pack", "Run `npm pack` in the specified directory and delete the resulting .tgz file afterwards")
   .option("-p, --from-npm", "Read from the npm registry instead of a local file")
+  .addOption(new Option("--definitely-typed [version]", "Specify the version range of @types to use").default(true))
+  .option("--no-definitely-typed", "Don't include @types")
   .addOption(new Option("-f, --format <format>", "Specify the print format").choices(formats).default("auto"))
   .option("-q, --quiet", "Don't print anything to STDOUT (overrides all other options)")
   .option(
@@ -92,6 +95,13 @@ particularly ESM-related module resolution issues.`
 
     let analysis: core.CheckResult;
     let deleteTgz;
+    const dtIsPath =
+      typeof opts.definitelyTyped === "string" &&
+      (opts.definitelyTyped.includes("/") ||
+        opts.definitelyTyped.includes("\\") ||
+        opts.definitelyTyped.endsWith(".tgz") ||
+        opts.definitelyTyped.endsWith(".tar.gz"));
+
     if (opts.fromNpm) {
       if (opts.pack) {
         program.error("--pack and --from-npm cannot be used together");
@@ -101,14 +111,18 @@ particularly ESM-related module resolution issues.`
         if (result.status === "error") {
           program.error(result.error);
         } else {
-          analysis = await core.checkPackage(
-            await core.createPackageFromNpm(`${result.data.name}@${result.data.version}`),
-            {
-              entrypoints: opts.entrypoints,
-              includeEntrypoints: opts.includeEntrypoints,
-              excludeEntrypoints: opts.excludeEntrypoints,
-            }
-          );
+          const pkg = dtIsPath
+            ? (await core.createPackageFromNpm(`${result.data.name}@${result.data.version}`)).mergedWithTypes(
+                core.createPackageFromTarballData(new Uint8Array(await readFile(opts.definitelyTyped as string)))
+              )
+            : await core.createPackageFromNpm(`${result.data.name}@${result.data.version}`, {
+                definitelyTyped: opts.definitelyTyped,
+              });
+          analysis = await core.checkPackage(pkg, {
+            entrypoints: opts.entrypoints,
+            includeEntrypoints: opts.includeEntrypoints,
+            excludeEntrypoints: opts.excludeEntrypoints,
+          });
         }
       } catch (error) {
         if (error instanceof FetchError) {
@@ -156,7 +170,14 @@ particularly ESM-related module resolution issues.`
         }
         const file = await readFile(fileName);
         const data = new Uint8Array(file);
-        analysis = await core.checkPackage(await core.createPackageFromTarballData(data), {
+        const pkg = dtIsPath
+          ? core
+              .createPackageFromTarballData(data)
+              .mergedWithTypes(
+                core.createPackageFromTarballData(new Uint8Array(await readFile(opts.definitelyTyped as string)))
+              )
+          : core.createPackageFromTarballData(data);
+        analysis = await core.checkPackage(pkg, {
           entrypoints: opts.entrypoints,
           includeEntrypoints: opts.includeEntrypoints,
           excludeEntrypoints: opts.excludeEntrypoints,
diff --git a/packages/cli/src/render/typed.ts b/packages/cli/src/render/typed.ts
index be61df1..ed8877c 100644
--- a/packages/cli/src/render/typed.ts
+++ b/packages/cli/src/render/typed.ts
@@ -31,6 +31,12 @@ export async function typed(analysis: core.Analysis, opts: Opts) {
     );
   }
 
+  console.log(`${analysis.packageName} v${analysis.packageVersion}`);
+  if (analysis.types.kind === "@types") {
+    console.log(`${analysis.types.packageName} v${analysis.types.packageVersion}`);
+  }
+  console.log();
+
   if (opts.summary) {
     const defaultSummary = marked(!opts.emoji ? " No problems found" : " No problems found 🌟");
     const summaryTexts = Object.keys(grouped).map((kind) => {
diff --git a/packages/cli/test/snapshots.test.ts b/packages/cli/test/snapshots.test.ts
index 51d8986..d0119c6 100644
--- a/packages/cli/test/snapshots.test.ts
+++ b/packages/cli/test/snapshots.test.ts
@@ -28,6 +28,15 @@ const tests = [
   ["vue@3.3.4.tgz", "--entrypoints . jsx-runtime"],
   ["vue@3.3.4.tgz", "--exclude-entrypoints macros -f ascii"],
   ["vue@3.3.4.tgz", "--include-entrypoints ./foo -f ascii"],
+
+  [
+    "big.js@6.2.1.tgz",
+    `--definitely-typed ${new URL("../../../core/test/fixtures/@types__big.js@6.2.0.tgz", import.meta.url).pathname}`,
+  ],
+  [
+    "react@18.2.0.tgz",
+    `--definitely-typed ${new URL("../../../core/test/fixtures/@types__react@18.2.21.tgz", import.meta.url).pathname}`,
+  ],
 ];
 
 const defaultOpts = "-f table-flipped";
diff --git a/packages/cli/test/snapshots/@apollo__client-3.7.16.tgz.md b/packages/cli/test/snapshots/@apollo__client-3.7.16.tgz.md
index 685cbdc..96effc4 100644
--- a/packages/cli/test/snapshots/@apollo__client-3.7.16.tgz.md
+++ b/packages/cli/test/snapshots/@apollo__client-3.7.16.tgz.md
@@ -4,6 +4,8 @@
 $ attw @apollo__client-3.7.16.tgz -f table-flipped
 
 
+@apollo/client v3.7.16
+
 👺 Import resolved to an ESM type declaration file, but a CommonJS JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseESM.md
 
 ⚠️ A require call resolved to an ESM JavaScript file, which is an error in Node and some bundlers. CommonJS consumers will need to use a dynamic import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSResolvesToESM.md
diff --git a/packages/cli/test/snapshots/@ice__app@3.2.6.tgz.md b/packages/cli/test/snapshots/@ice__app@3.2.6.tgz.md
index b87b5a8..d75c6ad 100644
--- a/packages/cli/test/snapshots/@ice__app@3.2.6.tgz.md
+++ b/packages/cli/test/snapshots/@ice__app@3.2.6.tgz.md
@@ -4,6 +4,8 @@
 $ attw @ice__app@3.2.6.tgz -f table-flipped
 
 
+@ice/app v3.2.6
+
 ⚠️ A require call resolved to an ESM JavaScript file, which is an error in Node and some bundlers. CommonJS consumers will need to use a dynamic import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSResolvesToESM.md
 
 💀 Import failed to resolve to type declarations or JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/NoResolution.md
diff --git a/packages/cli/test/snapshots/@reduxjs__toolkit@2.0.0-beta.0.tgz.md b/packages/cli/test/snapshots/@reduxjs__toolkit@2.0.0-beta.0.tgz.md
index 9eba234..eaa0119 100644
--- a/packages/cli/test/snapshots/@reduxjs__toolkit@2.0.0-beta.0.tgz.md
+++ b/packages/cli/test/snapshots/@reduxjs__toolkit@2.0.0-beta.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw @reduxjs__toolkit@2.0.0-beta.0.tgz -f table-flipped
 
 
+@reduxjs/toolkit v2.0.0-beta.0
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 🥴 Import found in a type declaration file failed to resolve. Either this indicates that runtime resolution errors will occur, or (more likely) the types misrepresent the contents of the JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/InternalResolutionError.md
diff --git a/packages/cli/test/snapshots/@vitejs__plugin-react@3.1.0.tgz.md b/packages/cli/test/snapshots/@vitejs__plugin-react@3.1.0.tgz.md
index cadfdf2..839db41 100644
--- a/packages/cli/test/snapshots/@vitejs__plugin-react@3.1.0.tgz.md
+++ b/packages/cli/test/snapshots/@vitejs__plugin-react@3.1.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw @vitejs__plugin-react@3.1.0.tgz -f table-flipped
 
 
+@vitejs/plugin-react v3.1.0
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 
diff --git a/packages/cli/test/snapshots/ajv@8.12.0.tgz.md b/packages/cli/test/snapshots/ajv@8.12.0.tgz.md
index 62c4ba8..900fa61 100644
--- a/packages/cli/test/snapshots/ajv@8.12.0.tgz.md
+++ b/packages/cli/test/snapshots/ajv@8.12.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw ajv@8.12.0.tgz -f table-flipped
 
 
+ajv v8.12.0
+
  No problems found 🌟
 
 
diff --git a/packages/cli/test/snapshots/astring@1.8.6.tgz.md b/packages/cli/test/snapshots/astring@1.8.6.tgz.md
index c4b5592..025d997 100644
--- a/packages/cli/test/snapshots/astring@1.8.6.tgz.md
+++ b/packages/cli/test/snapshots/astring@1.8.6.tgz.md
@@ -4,6 +4,8 @@
 $ attw astring@1.8.6.tgz -f table-flipped
 
 
+astring v1.8.6
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 
diff --git a/packages/cli/test/snapshots/axios@1.4.0.tgz.md b/packages/cli/test/snapshots/axios@1.4.0.tgz.md
index a17b923..31435de 100644
--- a/packages/cli/test/snapshots/axios@1.4.0.tgz.md
+++ b/packages/cli/test/snapshots/axios@1.4.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw axios@1.4.0.tgz -f table-flipped
 
 
+axios v1.4.0
+
 ❓ Wildcard subpaths cannot yet be analyzed by this tool. https://github.com/arethetypeswrong/arethetypeswrong.github.io/issues/40
 
 💀 Import failed to resolve to type declarations or JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/NoResolution.md
diff --git a/packages/cli/test/snapshots/big.js@6.2.1.tgz --definitely-typed UsersandrewDeveloperarethetypeswrong.github.iopackagescoretestfixtures@types__big.js@6.2.0.tgz.md b/packages/cli/test/snapshots/big.js@6.2.1.tgz --definitely-typed UsersandrewDeveloperarethetypeswrong.github.iopackagescoretestfixtures@types__big.js@6.2.0.tgz.md
new file mode 100644
index 0000000..eff546a
--- /dev/null
+++ b/packages/cli/test/snapshots/big.js@6.2.1.tgz --definitely-typed UsersandrewDeveloperarethetypeswrong.github.iopackagescoretestfixtures@types__big.js@6.2.0.tgz.md	
@@ -0,0 +1,33 @@
+# big.js@6.2.1.tgz --definitely-typed /Users/andrew/Developer/arethetypeswrong.github.io/packages/core/test/fixtures/@types__big.js@6.2.0.tgz
+
+```
+$ attw big.js@6.2.1.tgz --definitely-typed /Users/andrew/Developer/arethetypeswrong.github.io/packages/core/test/fixtures/@types__big.js@6.2.0.tgz
+
+
+big.js v6.2.1
+@types/big.js v6.2.0
+
+🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
+
+❌ Import resolved to JavaScript files, but no type declarations were found. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/UntypedResolution.md
+
+⚠️ A require call resolved to an ESM JavaScript file, which is an error in Node and some bundlers. CommonJS consumers will need to use a dynamic import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSResolvesToESM.md
+
+
+┌───────────────────┬────────────────────────┬──────────────────────────────┬─────────────────┬───────────────────────┐
+│                   │ "big.js"               │ "big.js/big.mjs"             │ "big.js/big.js" │ "big.js/package.json" │
+├───────────────────┼────────────────────────┼──────────────────────────────┼─────────────────┼───────────────────────┤
+│ node10            │ 🟢                     │ ❌ No types                  │ ❌ No types     │ 🟢 (JSON)             │
+├───────────────────┼────────────────────────┼──────────────────────────────┼─────────────────┼───────────────────────┤
+│ node16 (from CJS) │ 🟢 (CJS)               │ ❌ No types                  │ ❌ No types     │ 🟢 (JSON)             │
+│                   │                        │ ⚠️ ESM (dynamic import only) │                 │                       │
+├───────────────────┼────────────────────────┼──────────────────────────────┼─────────────────┼───────────────────────┤
+│ node16 (from ESM) │ 🎭 Masquerading as CJS │ ❌ No types                  │ ❌ No types     │ 🟢 (JSON)             │
+├───────────────────┼────────────────────────┼──────────────────────────────┼─────────────────┼───────────────────────┤
+│ bundler           │ 🟢                     │ ❌ No types                  │ ❌ No types     │ 🟢 (JSON)             │
+└───────────────────┴────────────────────────┴──────────────────────────────┴─────────────────┴───────────────────────┘
+
+
+```
+
+Exit code: 1
\ No newline at end of file
diff --git a/packages/cli/test/snapshots/commander@10.0.1.tgz -f table.md b/packages/cli/test/snapshots/commander@10.0.1.tgz -f table.md
index 2bcecd1..4a7cc93 100644
--- a/packages/cli/test/snapshots/commander@10.0.1.tgz -f table.md	
+++ b/packages/cli/test/snapshots/commander@10.0.1.tgz -f table.md	
@@ -4,6 +4,8 @@
 $ attw commander@10.0.1.tgz -f table
 
 
+commander v10.0.1
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 ❌ Import resolved to JavaScript files, but no type declarations were found. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/UntypedResolution.md
diff --git a/packages/cli/test/snapshots/hexoid@1.0.0.tgz.md b/packages/cli/test/snapshots/hexoid@1.0.0.tgz.md
index 81c17ca..0a9545f 100644
--- a/packages/cli/test/snapshots/hexoid@1.0.0.tgz.md
+++ b/packages/cli/test/snapshots/hexoid@1.0.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw hexoid@1.0.0.tgz -f table-flipped
 
 
+hexoid v1.0.0
+
 ❗️ The resolved types use export default where the JavaScript file appears to use module.exports =. This will cause TypeScript under the node16 module mode to think an extra .default property access is required, but that will likely fail at runtime. These types should use export = instead of export default. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseExportDefault.md
 
 
diff --git a/packages/cli/test/snapshots/klona@2.0.6.tgz -f ascii.md b/packages/cli/test/snapshots/klona@2.0.6.tgz -f ascii.md
index a247192..8f1da2a 100644
--- a/packages/cli/test/snapshots/klona@2.0.6.tgz -f ascii.md	
+++ b/packages/cli/test/snapshots/klona@2.0.6.tgz -f ascii.md	
@@ -4,6 +4,8 @@
 $ attw klona@2.0.6.tgz -f ascii
 
 
+klona v2.0.6
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 
diff --git a/packages/cli/test/snapshots/node-html-parser@6.1.5.tgz.md b/packages/cli/test/snapshots/node-html-parser@6.1.5.tgz.md
index 00534df..98b91c5 100644
--- a/packages/cli/test/snapshots/node-html-parser@6.1.5.tgz.md
+++ b/packages/cli/test/snapshots/node-html-parser@6.1.5.tgz.md
@@ -4,6 +4,8 @@
 $ attw node-html-parser@6.1.5.tgz -f table-flipped
 
 
+node-html-parser v6.1.5
+
 🤨 CommonJS module simulates a default export with exports.default and exports.__esModule, but does not also set module.exports for compatibility with Node. Node, and some bundlers under certain conditions (https://andrewbranch.github.io/interop-test/#synthesizing-default-exports-for-cjs-modules), do not respect the __esModule marker, so accessing the intended default export will require a .default property access on the default import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSOnlyExportsDefault.md
 
 
diff --git a/packages/cli/test/snapshots/postcss@8.4.21.tgz.md b/packages/cli/test/snapshots/postcss@8.4.21.tgz.md
index 221bd21..de320ed 100644
--- a/packages/cli/test/snapshots/postcss@8.4.21.tgz.md
+++ b/packages/cli/test/snapshots/postcss@8.4.21.tgz.md
@@ -4,6 +4,8 @@
 $ attw postcss@8.4.21.tgz -f table-flipped
 
 
+postcss v8.4.21
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 🐛 Import resolved to types through a conditional package.json export, but only after failing to resolve through an earlier condition. This behavior is a TypeScript bug (https://github.com/microsoft/TypeScript/issues/50762). It may misrepresent the runtime behavior of this import and should not be relied upon. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FallbackCondition.md
diff --git a/packages/cli/test/snapshots/react-chartjs-2@5.2.0.tgz.md b/packages/cli/test/snapshots/react-chartjs-2@5.2.0.tgz.md
index 6be800c..740c069 100644
--- a/packages/cli/test/snapshots/react-chartjs-2@5.2.0.tgz.md
+++ b/packages/cli/test/snapshots/react-chartjs-2@5.2.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw react-chartjs-2@5.2.0.tgz -f table-flipped
 
 
+react-chartjs-2 v5.2.0
+
 👺 Import resolved to an ESM type declaration file, but a CommonJS JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseESM.md
 
 ⚠️ A require call resolved to an ESM JavaScript file, which is an error in Node and some bundlers. CommonJS consumers will need to use a dynamic import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSResolvesToESM.md
diff --git a/packages/cli/test/snapshots/react@18.2.0.tgz --definitely-typed UsersandrewDeveloperarethetypeswrong.github.iopackagescoretestfixtures@types__react@18.2.21.tgz.md b/packages/cli/test/snapshots/react@18.2.0.tgz --definitely-typed UsersandrewDeveloperarethetypeswrong.github.iopackagescoretestfixtures@types__react@18.2.21.tgz.md
new file mode 100644
index 0000000..96dd4cc
--- /dev/null
+++ b/packages/cli/test/snapshots/react@18.2.0.tgz --definitely-typed UsersandrewDeveloperarethetypeswrong.github.iopackagescoretestfixtures@types__react@18.2.21.tgz.md	
@@ -0,0 +1,32 @@
+# react@18.2.0.tgz --definitely-typed /Users/andrew/Developer/arethetypeswrong.github.io/packages/core/test/fixtures/@types__react@18.2.21.tgz
+
+```
+$ attw react@18.2.0.tgz --definitely-typed /Users/andrew/Developer/arethetypeswrong.github.io/packages/core/test/fixtures/@types__react@18.2.21.tgz
+
+
+react v18.2.0
+@types/react v18.2.21
+
+ No problems found 🌟
+
+
+┌─────────────────────────┬───────────┬───────────────────┬───────────────────┬───────────┐
+│                         │ node10    │ node16 (from CJS) │ node16 (from ESM) │ bundler   │
+├─────────────────────────┼───────────┼───────────────────┼───────────────────┼───────────┤
+│ "react"                 │ 🟢        │ 🟢 (CJS)          │ 🟢 (CJS)          │ 🟢        │
+├─────────────────────────┼───────────┼───────────────────┼───────────────────┼───────────┤
+│ "react/package.json"    │ 🟢 (JSON) │ 🟢 (JSON)         │ 🟢 (JSON)         │ 🟢 (JSON) │
+├─────────────────────────┼───────────┼───────────────────┼───────────────────┼───────────┤
+│ "react/jsx-runtime"     │ 🟢        │ 🟢 (CJS)          │ 🟢 (CJS)          │ 🟢        │
+├─────────────────────────┼───────────┼───────────────────┼───────────────────┼───────────┤
+│ "react/jsx-dev-runtime" │ 🟢        │ 🟢 (CJS)          │ 🟢 (CJS)          │ 🟢        │
+├─────────────────────────┼───────────┼───────────────────┼───────────────────┼───────────┤
+│ "react/canary"          │ 🟢        │ 🟢 (CJS)          │ 🟢 (CJS)          │ 🟢        │
+├─────────────────────────┼───────────┼───────────────────┼───────────────────┼───────────┤
+│ "react/experimental"    │ 🟢        │ 🟢 (CJS)          │ 🟢 (CJS)          │ 🟢        │
+└─────────────────────────┴───────────┴───────────────────┴───────────────────┴───────────┘
+
+
+```
+
+Exit code: 0
\ No newline at end of file
diff --git a/packages/cli/test/snapshots/rfdc@1.3.0.tgz.md b/packages/cli/test/snapshots/rfdc@1.3.0.tgz.md
index 44b9a37..cb319af 100644
--- a/packages/cli/test/snapshots/rfdc@1.3.0.tgz.md
+++ b/packages/cli/test/snapshots/rfdc@1.3.0.tgz.md
@@ -4,6 +4,8 @@
 $ attw rfdc@1.3.0.tgz -f table-flipped
 
 
+rfdc v1.3.0
+
 ❌ Import resolved to JavaScript files, but no type declarations were found. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/UntypedResolution.md
 
 
diff --git a/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints . jsx-runtime.md b/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints . jsx-runtime.md
index 482aa2f..d763b4b 100644
--- a/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints . jsx-runtime.md	
+++ b/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints . jsx-runtime.md	
@@ -4,6 +4,8 @@
 $ attw vue@3.3.4.tgz --entrypoints . jsx-runtime
 
 
+vue v3.3.4
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 🥴 Import found in a type declaration file failed to resolve. Either this indicates that runtime resolution errors will occur, or (more likely) the types misrepresent the contents of the JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/InternalResolutionError.md
diff --git a/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints vue.md b/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints vue.md
index fce301d..0179660 100644
--- a/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints vue.md	
+++ b/packages/cli/test/snapshots/vue@3.3.4.tgz --entrypoints vue.md	
@@ -4,6 +4,8 @@
 $ attw vue@3.3.4.tgz --entrypoints vue
 
 
+vue v3.3.4
+
 🥴 Import found in a type declaration file failed to resolve. Either this indicates that runtime resolution errors will occur, or (more likely) the types misrepresent the contents of the JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/InternalResolutionError.md
 
 
diff --git a/packages/cli/test/snapshots/vue@3.3.4.tgz --exclude-entrypoints macros -f ascii.md b/packages/cli/test/snapshots/vue@3.3.4.tgz --exclude-entrypoints macros -f ascii.md
index 473e225..65f8b6e 100644
--- a/packages/cli/test/snapshots/vue@3.3.4.tgz --exclude-entrypoints macros -f ascii.md	
+++ b/packages/cli/test/snapshots/vue@3.3.4.tgz --exclude-entrypoints macros -f ascii.md	
@@ -4,6 +4,8 @@
 $ attw vue@3.3.4.tgz --exclude-entrypoints macros -f ascii
 
 
+vue v3.3.4
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 💀 Import failed to resolve to type declarations or JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/NoResolution.md
diff --git a/packages/cli/test/snapshots/vue@3.3.4.tgz --include-entrypoints .foo -f ascii.md b/packages/cli/test/snapshots/vue@3.3.4.tgz --include-entrypoints .foo -f ascii.md
index 8333bb1..926827b 100644
--- a/packages/cli/test/snapshots/vue@3.3.4.tgz --include-entrypoints .foo -f ascii.md	
+++ b/packages/cli/test/snapshots/vue@3.3.4.tgz --include-entrypoints .foo -f ascii.md	
@@ -4,6 +4,8 @@
 $ attw vue@3.3.4.tgz --include-entrypoints ./foo -f ascii
 
 
+vue v3.3.4
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 💀 Import failed to resolve to type declarations or JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/NoResolution.md
diff --git a/packages/cli/test/snapshots/vue@3.3.4.tgz.md b/packages/cli/test/snapshots/vue@3.3.4.tgz.md
index 549caf9..9974d36 100644
--- a/packages/cli/test/snapshots/vue@3.3.4.tgz.md
+++ b/packages/cli/test/snapshots/vue@3.3.4.tgz.md
@@ -4,6 +4,8 @@
 $ attw vue@3.3.4.tgz -f table-flipped
 
 
+vue v3.3.4
+
 🎭 Import resolved to a CommonJS type declaration file, but an ESM JavaScript file. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseCJS.md
 
 💀 Import failed to resolve to type declarations or JavaScript files. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/NoResolution.md
diff --git a/packages/core/src/checkPackage.ts b/packages/core/src/checkPackage.ts
index 1b3badb..ed5d5a9 100644
--- a/packages/core/src/checkPackage.ts
+++ b/packages/core/src/checkPackage.ts
@@ -4,7 +4,14 @@ import { getFileProblems } from "./checks/fileProblems.js";
 import { getResolutionBasedFileProblems } from "./checks/resolutionBasedFileProblems.js";
 import type { Package } from "./createPackage.js";
 import { createCompilerHosts, type CompilerHosts, CompilerHostWrapper } from "./multiCompilerHost.js";
-import type { CheckResult, EntrypointInfo, EntrypointResolutionAnalysis, Resolution, ResolutionKind } from "./types.js";
+import type {
+  AnalysisTypes,
+  CheckResult,
+  EntrypointInfo,
+  EntrypointResolutionAnalysis,
+  Resolution,
+  ResolutionKind,
+} from "./types.js";
 
 export interface CheckPackageOptions {
   /**
@@ -24,15 +31,17 @@ export interface CheckPackageOptions {
 }
 
 export async function checkPackage(pkg: Package, options?: CheckPackageOptions): Promise<CheckResult> {
-  const files = pkg.listFiles();
-  const types = files.some(ts.hasTSFileExtension) ? "included" : false;
-  const parts = files[0].split("/");
-  let packageName = parts[2];
-  if (packageName.startsWith("@")) {
-    packageName = parts.slice(2, 4).join("/");
-  }
-  const packageJsonContent = JSON.parse(pkg.readFile(`/node_modules/${packageName}/package.json`));
-  const packageVersion = packageJsonContent.version;
+  const types: AnalysisTypes | false = pkg.typesPackage
+    ? {
+        kind: "@types",
+        ...pkg.typesPackage,
+        definitelyTypedUrl: JSON.parse(pkg.readFile(`/node_modules/${pkg.typesPackage.packageName}/package.json`))
+          .homepage,
+      }
+    : pkg.containsTypes()
+    ? { kind: "included" }
+    : false;
+  const { packageName, packageVersion } = pkg;
   if (!types) {
     return { packageName, packageVersion, types };
   }
@@ -131,7 +140,12 @@ function getEntrypointInfo(
   options: CheckPackageOptions | undefined
 ): Record<string, EntrypointInfo> {
   const packageJson = JSON.parse(fs.readFile(`/node_modules/${packageName}/package.json`));
-  const entrypoints = getEntrypoints(fs, packageJson.exports, options);
+  let entrypoints = getEntrypoints(fs, packageJson.exports, options);
+  if (fs.typesPackage) {
+    const typesPackageJson = JSON.parse(fs.readFile(`/node_modules/${fs.typesPackage.packageName}/package.json`));
+    const typesEntrypoints = getEntrypoints(fs, typesPackageJson.exports, options);
+    entrypoints = unique([...entrypoints, ...typesEntrypoints]);
+  }
   const result: Record<string, EntrypointInfo> = {};
   for (const entrypoint of entrypoints) {
     const resolutions: Record<ResolutionKind, EntrypointResolutionAnalysis> = {
diff --git a/packages/core/src/createPackage.ts b/packages/core/src/createPackage.ts
index 88adb7f..03d7c11 100644
--- a/packages/core/src/createPackage.ts
+++ b/packages/core/src/createPackage.ts
@@ -1,50 +1,197 @@
 import { untar } from "@andrewbranch/untar.js";
 import { gunzipSync } from "fflate";
 import ts from "typescript";
-import { parsePackageSpec } from "./utils.js";
-import { maxSatisfying } from "semver";
-
-export interface Package {
-  packageName: string;
-  packageVersion: string;
-  readFile: (path: string) => string;
-  fileExists: (path: string) => boolean;
-  directoryExists: (path: string) => boolean;
-  listFiles: () => string[];
+import { parsePackageSpec, type ParsedPackageSpec } from "./utils.js";
+import { maxSatisfying, major, minor, valid, validRange } from "semver";
+
+export class Package {
+  #files: Record<string, string | Uint8Array> = {};
+  readonly packageName: string;
+  readonly packageVersion: string;
+  readonly typesPackage?: {
+    packageName: string;
+    packageVersion: string;
+  };
+
+  constructor(
+    files: Record<string, string | Uint8Array>,
+    packageName: string,
+    packageVersion: string,
+    typesPackage?: {
+      packageName: string;
+      packageVersion: string;
+    }
+  ) {
+    this.#files = files;
+    this.packageName = packageName;
+    this.packageVersion = packageVersion;
+    this.typesPackage = typesPackage;
+  }
+
+  readFile(path: string): string {
+    const file = this.#files[path];
+    if (!file) {
+      throw new Error(`File not found: ${path}`);
+    }
+    if (typeof file === "string") {
+      return file;
+    }
+    const content = new TextDecoder().decode(file);
+    this.#files[path] = content;
+    return content;
+  }
+
+  fileExists(path: string): boolean {
+    return path in this.#files;
+  }
+
+  directoryExists(path: string): boolean {
+    path = ts.ensureTrailingDirectorySeparator(path);
+    for (const file in this.#files) {
+      if (file.startsWith(path)) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  containsTypes(directory = "/"): boolean {
+    return this.listFiles(directory).some(ts.hasTSFileExtension);
+  }
+
+  listFiles(directory = "/"): string[] {
+    directory = ts.ensureTrailingDirectorySeparator(directory);
+    return directory === "/"
+      ? Object.keys(this.#files)
+      : Object.keys(this.#files).filter((f) => f.startsWith(directory));
+  }
+
+  mergedWithTypes(typesPackage: Package): Package {
+    const files = { ...this.#files, ...typesPackage.#files };
+    return new Package(files, this.packageName, this.packageVersion, {
+      packageName: typesPackage.packageName,
+      packageVersion: typesPackage.packageVersion,
+    });
+  }
+}
+
+export interface CreatePackageFromNpmOptions {
+  /**
+   * Controls inclusion of a corresponding `@types` package. Ignored if the implementation
+   * package contains TypeScript files. The value is the version or SemVer range of the
+   * `@types` package to include, `true` to infer the version from the implementation
+   * package version, or `false` to prevent inclusion of a `@types` package.
+   * @default true
+   */
+  definitelyTyped?: string | boolean;
 }
 
-export async function createPackageFromNpm(packageSpec: string): Promise<Package> {
+export async function createPackageFromNpm(
+  packageSpec: string,
+  { definitelyTyped = true }: CreatePackageFromNpmOptions = {}
+): Promise<Package> {
   const parsed = parsePackageSpec(packageSpec);
   if (parsed.status === "error") {
     throw new Error(parsed.error);
   }
   const packageName = parsed.data.name;
-  const packageVersion = parsed.data.version || "latest";
+  const spec =
+    parsed.data.versionKind === "none" && typeof definitelyTyped === "string"
+      ? parsePackageSpec(`${packageName}@${definitelyTyped}`)
+      : parsed;
+  const { tarballUrl, version } = await getNpmTarballUrl(spec.data || parsed.data);
+  const pkg = await createPackageFromTarballUrl(tarballUrl);
+  if (!definitelyTyped || pkg.containsTypes()) {
+    return pkg;
+  }
+
+  const typesPackageName = ts.getTypesPackageName(packageName);
+  let typesPackageData;
+  if (definitelyTyped === true) {
+    try {
+      typesPackageData = await getNpmTarballUrl({
+        name: typesPackageName,
+        versionKind: "range",
+        version: `${major(version)}.${minor(version)}`,
+      });
+    } catch {
+      try {
+        typesPackageData = await getNpmTarballUrl({
+          name: typesPackageName,
+          versionKind: "range",
+          version: `${major(version)}`,
+        });
+      } catch {
+        try {
+          typesPackageData = await getNpmTarballUrl({
+            name: typesPackageName,
+            versionKind: "tag",
+            version: "latest",
+          });
+        } catch {
+          typesPackageData = undefined;
+        }
+      }
+    }
+  } else {
+    typesPackageData = await getNpmTarballUrl({
+      name: typesPackageName,
+      versionKind: valid(definitelyTyped) ? "exact" : validRange(definitelyTyped) ? "range" : "tag",
+      version: definitelyTyped,
+    });
+  }
+
+  if (typesPackageData) {
+    return pkg.mergedWithTypes(await createPackageFromTarballUrl(typesPackageData.tarballUrl));
+  }
+  return pkg;
+}
+
+async function getNpmTarballUrl(packageSpec: ParsedPackageSpec): Promise<{ tarballUrl: string; version: string }> {
   const registryUrl =
-    parsed.data.versionKind === "range"
-      ? `https://registry.npmjs.org/${packageName}`
-      : `https://registry.npmjs.org/${packageName}/${packageVersion}`;
-  const Accept = parsed.data.versionKind === "range" ? "application/vnd.npm.install-v1+json" : "application/json";
+    packageSpec.versionKind === "range" || (packageSpec.versionKind === "tag" && packageSpec.version !== "latest")
+      ? `https://registry.npmjs.org/${packageSpec.name}`
+      : `https://registry.npmjs.org/${packageSpec.name}/${packageSpec.version || "latest"}`;
+  const Accept =
+    packageSpec.versionKind === "range" || (packageSpec.versionKind === "tag" && packageSpec.version !== "latest")
+      ? "application/vnd.npm.install-v1+json"
+      : "application/json";
   const doc = await fetch(registryUrl, { headers: { Accept } }).then((r) => r.json());
-  let tarballUrl;
-  if (parsed.data.versionKind === "range") {
-    const version = maxSatisfying(Object.keys(doc.versions), parsed.data.version);
+  let tarballUrl, version;
+  if (packageSpec.versionKind === "range") {
+    version = maxSatisfying(Object.keys(doc.versions), packageSpec.version);
     if (!version) {
-      throw new Error(`No version found matching '${packageVersion}'`);
+      throw new Error(`No version found matching '${packageSpec.version}'`);
+    }
+    tarballUrl = doc.versions[version].dist.tarball;
+  } else if (packageSpec.versionKind === "tag" && packageSpec.version !== "latest") {
+    version = doc["dist-tags"][packageSpec.version];
+    if (!version) {
+      throw new Error(`No version found matching '${packageSpec.version}'`);
     }
     tarballUrl = doc.versions[version].dist.tarball;
   } else {
+    version = doc.version;
     tarballUrl = doc.dist.tarball;
   }
-  return createPackageFromTarballUrl(tarballUrl);
+  return { version, tarballUrl };
 }
 
 export async function createPackageFromTarballUrl(tarballUrl: string): Promise<Package> {
-  const tarball = new Uint8Array((await fetch(tarballUrl).then((r) => r.arrayBuffer())) satisfies ArrayBuffer);
+  const tarball = await fetchTarball(tarballUrl);
   return createPackageFromTarballData(tarball);
 }
 
-export async function createPackageFromTarballData(tarball: Uint8Array): Promise<Package> {
+async function fetchTarball(tarballUrl: string) {
+  return new Uint8Array((await fetch(tarballUrl).then((r) => r.arrayBuffer())) satisfies ArrayBuffer);
+}
+
+export function createPackageFromTarballData(tarball: Uint8Array): Package {
+  const { files, packageName, packageVersion } = extractTarball(tarball);
+  return new Package(files, packageName, packageVersion);
+}
+
+function extractTarball(tarball: Uint8Array) {
   const data = untar(gunzipSync(tarball));
   const prefix = data[0].filename.substring(0, data[0].filename.indexOf("/") + 1);
   const packageJsonText = data.find((f) => f.filename === `${prefix}package.json`)?.fileData;
@@ -55,27 +202,5 @@ export async function createPackageFromTarballData(tarball: Uint8Array): Promise
     acc[ts.combinePaths("/node_modules/" + packageName, file.filename.substring(prefix.length))] = file.fileData;
     return acc;
   }, {});
-
-  return {
-    packageName,
-    packageVersion,
-    readFile: (path: string) => {
-      const file = files[path];
-      if (!file) {
-        throw new Error(`File not found: ${path}`);
-      }
-      return new TextDecoder().decode(file);
-    },
-    fileExists: (path: string) => path in files,
-    directoryExists: (path: string) => {
-      path = ts.ensureTrailingDirectorySeparator(path);
-      for (const file in files) {
-        if (file.startsWith(path)) {
-          return true;
-        }
-      }
-      return false;
-    },
-    listFiles: () => Object.keys(files),
-  };
+  return { files, packageName, packageVersion };
 }
diff --git a/packages/core/src/multiCompilerHost.ts b/packages/core/src/multiCompilerHost.ts
index fc33d2f..6e1a0b2 100644
--- a/packages/core/src/multiCompilerHost.ts
+++ b/packages/core/src/multiCompilerHost.ts
@@ -128,7 +128,9 @@ export class CompilerHostWrapper {
   private createCompilerHost(fs: Package): ts.CompilerHost {
     const sourceFileCache = new Map<ts.Path, ts.SourceFile>();
     return {
-      ...fs,
+      fileExists: fs.fileExists.bind(fs),
+      readFile: fs.readFile.bind(fs),
+      directoryExists: fs.directoryExists.bind(fs),
       getSourceFile: (fileName) => {
         const path = toPath(fileName);
         const cached = sourceFileCache.get(path);
diff --git a/packages/core/src/types.ts b/packages/core/src/types.ts
index 4b777c9..7542536 100644
--- a/packages/core/src/types.ts
+++ b/packages/core/src/types.ts
@@ -9,10 +9,21 @@ export interface EntrypointInfo {
   isWildcard: boolean;
 }
 
+export interface IncludedTypes {
+  kind: "included";
+}
+export interface TypesPackage {
+  kind: "@types";
+  packageName: string;
+  packageVersion: string;
+  definitelyTypedUrl?: string;
+}
+export type AnalysisTypes = IncludedTypes | TypesPackage;
+
 export interface Analysis {
   packageName: string;
   packageVersion: string;
-  types: "included";
+  types: AnalysisTypes;
   entrypoints: Record<string, EntrypointInfo>;
   problems: Problem[];
 }
@@ -98,10 +109,10 @@ export type ProblemKind = Problem["kind"];
 export type FileProblemKind = FileProblem["kind"];
 export type ResolutionBasedFileProblemKind = ResolutionBasedFileProblem["kind"];
 
-export type Failable<T> = { status: "error"; error: string } | { status: "success"; data: T };
+export type Failable<T> = { status: "error"; error: string; data?: never } | { status: "success"; data: T };
 
 export interface ParsedPackageSpec {
   name: string;
-  versionKind: "none" | "exact" | "range";
+  versionKind: "none" | "exact" | "range" | "tag";
   version: string;
 }
diff --git a/packages/core/src/utils.ts b/packages/core/src/utils.ts
index 051059f..5485dca 100644
--- a/packages/core/src/utils.ts
+++ b/packages/core/src/utils.ts
@@ -160,12 +160,6 @@ export function parsePackageSpec(input: string): Failable<ParsedPackageSpec> {
         error: "Invalid package name",
       };
     }
-    if (input.substring(0, i) === "@types") {
-      return {
-        status: "error",
-        error: "@types packages are not supported",
-      };
-    }
     i++;
   }
   i = input.indexOf("@", i);
@@ -201,7 +195,7 @@ export function parsePackageSpec(input: string): Failable<ParsedPackageSpec> {
     };
   }
   return {
-    status: "error",
-    error: "Invalid version",
+    status: "success",
+    data: { versionKind: "tag", name, version },
   };
 }
diff --git a/packages/core/test/fixtures/@types__big.js@6.2.0.tgz b/packages/core/test/fixtures/@types__big.js@6.2.0.tgz
new file mode 100644
index 0000000..1346ca6
Binary files /dev/null and b/packages/core/test/fixtures/@types__big.js@6.2.0.tgz differ
diff --git a/packages/core/test/fixtures/@types__react@18.2.21.tgz b/packages/core/test/fixtures/@types__react@18.2.21.tgz
new file mode 100644
index 0000000..256624d
Binary files /dev/null and b/packages/core/test/fixtures/@types__react@18.2.21.tgz differ
diff --git a/packages/core/test/fixtures/big.js@6.2.1.tgz b/packages/core/test/fixtures/big.js@6.2.1.tgz
new file mode 100644
index 0000000..2debf14
Binary files /dev/null and b/packages/core/test/fixtures/big.js@6.2.1.tgz differ
diff --git a/packages/core/test/fixtures/react@18.2.0.tgz b/packages/core/test/fixtures/react@18.2.0.tgz
new file mode 100644
index 0000000..6cb2cb9
Binary files /dev/null and b/packages/core/test/fixtures/react@18.2.0.tgz differ
diff --git a/packages/core/test/snapshots.test.ts b/packages/core/test/snapshots.test.ts
index 665b222..d9eaa96 100644
--- a/packages/core/test/snapshots.test.ts
+++ b/packages/core/test/snapshots.test.ts
@@ -21,13 +21,24 @@ describe("snapshots", async () => {
     }
   });
 
+  const typesPackages: Record<string, string> = {
+    "big.js@6.2.1.tgz": "@types__big.js@6.2.0.tgz",
+    "react@18.2.0.tgz": "@types__react@18.2.21.tgz",
+  };
+
   for (const fixture of fs.readdirSync(new URL("../fixtures", import.meta.url))) {
-    if (fixture === ".DS_Store") {
+    if (fixture === ".DS_Store" || fixture.startsWith("@types__")) {
       continue;
     }
     test(fixture, async () => {
       const tarball = await readFile(new URL(`../fixtures/${fixture}`, import.meta.url));
-      const analysis = await checkPackage(await createPackageFromTarballData(tarball));
+      const typesTarball = typesPackages[fixture]
+        ? await readFile(new URL(`../fixtures/${typesPackages[fixture]}`, import.meta.url))
+        : undefined;
+      const pkg = createPackageFromTarballData(tarball);
+      const analysis = await checkPackage(
+        typesTarball ? pkg.mergedWithTypes(createPackageFromTarballData(typesTarball)) : pkg
+      );
       const snapshotURL = new URL(`../snapshots/${fixture}.md`, import.meta.url);
       const expectedSnapshot = [
         `# ${fixture}`,
diff --git a/packages/core/test/snapshots/big.js@6.2.1.tgz.md b/packages/core/test/snapshots/big.js@6.2.1.tgz.md
new file mode 100644
index 0000000..ac48955
--- /dev/null
+++ b/packages/core/test/snapshots/big.js@6.2.1.tgz.md
@@ -0,0 +1,58 @@
+# big.js@6.2.1.tgz
+
+## Problems
+
+```json
+[
+  {
+    "kind": "FalseCJS",
+    "entrypoint": ".",
+    "resolutionKind": "node16-esm"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.mjs",
+    "resolutionKind": "node10"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.mjs",
+    "resolutionKind": "node16-cjs"
+  },
+  {
+    "kind": "CJSResolvesToESM",
+    "entrypoint": "./big.mjs",
+    "resolutionKind": "node16-cjs"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.mjs",
+    "resolutionKind": "node16-esm"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.mjs",
+    "resolutionKind": "bundler"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.js",
+    "resolutionKind": "node10"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.js",
+    "resolutionKind": "node16-cjs"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.js",
+    "resolutionKind": "node16-esm"
+  },
+  {
+    "kind": "UntypedResolution",
+    "entrypoint": "./big.js",
+    "resolutionKind": "bundler"
+  }
+]
+```
\ No newline at end of file
diff --git a/packages/core/test/snapshots/react@18.2.0.tgz.md b/packages/core/test/snapshots/react@18.2.0.tgz.md
new file mode 100644
index 0000000..1b51016
--- /dev/null
+++ b/packages/core/test/snapshots/react@18.2.0.tgz.md
@@ -0,0 +1,7 @@
+# react@18.2.0.tgz
+
+## Problems
+
+```json
+[]
+```
\ No newline at end of file
diff --git a/packages/web/src/index.html b/packages/web/src/index.html
index 4e166c0..1041a47 100644
--- a/packages/web/src/index.html
+++ b/packages/web/src/index.html
@@ -43,7 +43,7 @@ <h1>Are the types wrong?</h1>
         </p>
         <div id="message"></div>
       </form>
-      <h2 id="package-info" class="display-none"></h2>
+      <div id="package-info" class="display-none"></div>
       <p id="problems"></p>
       <div><table id="resolutions"></table></div>
       <div id="details" class="display-none"></div>
diff --git a/packages/web/src/renderer.ts b/packages/web/src/renderer.ts
index c26be33..8705a15 100644
--- a/packages/web/src/renderer.ts
+++ b/packages/web/src/renderer.ts
@@ -59,10 +59,7 @@ export function subscribeRenderer(events: Events) {
     function render(prevState: State) {
       const state = getState();
       updateView(messageElement, Message, { isError: state.message?.isError, text: state.message?.text || "" });
-      updateView(packageInfoElement, PackageInfo, {
-        name: state.analysis?.packageName,
-        version: state.analysis?.packageVersion,
-      });
+      updateView(packageInfoElement, PackageInfo, { analysis: state.analysis?.types ? state.analysis : undefined });
       updateView(problemsElement, ProblemList, { analysis: state.analysis });
       updateView(resolutionsElement, ChecksTable, { analysis: state.analysis });
       updateView(checkButton, CheckButton, { disabled: !state.packageInfo.parsed });
diff --git a/packages/web/src/views/PackageInfo.ts b/packages/web/src/views/PackageInfo.ts
index d46bf2d..4de60d5 100644
--- a/packages/web/src/views/PackageInfo.ts
+++ b/packages/web/src/views/PackageInfo.ts
@@ -1,14 +1,32 @@
-export function PackageInfo(props: { name?: string; version?: string }) {
-  if (!props.name || !props.version) {
+import type { Analysis } from "@arethetypeswrong/core/types";
+
+export function PackageInfo({ analysis }: { analysis?: Analysis }) {
+  if (!analysis) {
     return { className: "display-none" };
   }
   return {
     className: "",
     innerHTML: `
-      ${props.name} v${props.version}
-      <small>
-        (<a href="https://npmjs.com/${props.name}">npm</a>,
-        <a href="https://unpkg.com/browse/${props.name}@${props.version}/">unpkg</a>)
-      </small>`,
+      <h2>
+        ${analysis.packageName} v${analysis.packageVersion}
+        <small>
+          (<a href="https://npmjs.com/${analysis.packageName}">npm</a>,
+          <a href="https://unpkg.com/browse/${analysis.packageName}@${analysis.packageVersion}/">unpkg</a>)
+        </small>
+      </h2>
+      ${
+        analysis.types.kind === "@types"
+          ? `
+        <h2>
+          ${analysis.types.packageName} v${analysis.types.packageVersion}
+          <small>
+            (<a href="https://npmjs.com/${analysis.types.packageName}">npm</a>,
+            <a href="https://unpkg.com/browse/${analysis.types.packageName}@${analysis.types.packageVersion}/">unpkg</a>,
+            <a href="${analysis.types.definitelyTypedUrl}">DefinitelyTyped</a>)
+          </small>
+        </h2>
+      `
+          : ""
+      }`,
   };
 }
diff --git a/packages/web/worker/worker.ts b/packages/web/worker/worker.ts
index 0510143..9defa0c 100644
--- a/packages/web/worker/worker.ts
+++ b/packages/web/worker/worker.ts
@@ -4,6 +4,7 @@ import {
   createPackageFromTarballData,
   type CheckResult,
 } from "@arethetypeswrong/core";
+import { parsePackageSpec } from "@arethetypeswrong/core/utils";
 
 export interface CheckPackageEventData {
   kind: "check-package";
@@ -25,7 +26,11 @@ export interface ResultMessage {
 onmessage = async (event: MessageEvent<CheckPackageEventData | CheckFileEventData>) => {
   const result = await checkPackage(
     event.data.kind === "check-file"
-      ? await createPackageFromTarballData(event.data.file)
+      ? createPackageFromTarballData(event.data.file)
+      : event.data.packageSpec.startsWith("@types/")
+      ? await createPackageFromNpm(unmangleScopedPackageName(event.data.packageSpec), {
+          definitelyTyped: parsePackageSpec(event.data.packageSpec).data?.version,
+        })
       : await createPackageFromNpm(event.data.packageSpec)
   );
   postMessage({
@@ -35,3 +40,7 @@ onmessage = async (event: MessageEvent<CheckPackageEventData | CheckFileEventDat
     },
   } satisfies ResultMessage);
 };
+
+function unmangleScopedPackageName(packageName: string): string {
+  return packageName.startsWith("@types/") ? packageName.slice(7).replace("__", "/") : packageName;
+}