diff --git a/next/json-schema-test-suite b/next/json-schema-test-suite
new file mode 160000
index 00000000..e524505b
--- /dev/null
+++ b/next/json-schema-test-suite
@@ -0,0 +1 @@
+Subproject commit e524505b8ac4a61c5dc162b51d68c2385a134706
diff --git a/src/form.ts b/src/form.ts
index 11334419..7af93a90 100644
--- a/src/form.ts
+++ b/src/form.ts
@@ -5,6 +5,7 @@ import type { LegacyOptions } from './validation/schema'
 import { getErrorMessage } from './errors/messages'
 import { buildFieldSchema } from './field/schema'
 import { calculateFinalSchema, updateFieldProperties } from './mutations'
+import { addCustomJsonLogicOperations, removeCustomJsonLogicOperations } from './validation/json-logic'
 import { validateSchema } from './validation/schema'
 
 export { LegacyOptions } from './validation/schema'
@@ -228,6 +229,11 @@ export interface CreateHeadlessFormOptions {
    * @default false
    */
   strictInputType?: boolean
+
+  /**
+   * Custom user defined functions. A dictionary of name and function
+   */
+  customJsonLogicOps?: Record<string, (...args: any[]) => any>
 }
 
 function buildFields(params: { schema: JsfObjectSchema, originalSchema: JsfObjectSchema, strictInputType?: boolean }): Field[] {
@@ -251,6 +257,20 @@ function validateOptions(options: CreateHeadlessFormOptions) {
   if (Object.prototype.hasOwnProperty.call(options, 'customProperties')) {
     console.error('[json-schema-form] `customProperties` is a deprecated option and it\'s not supported on json-schema-form v1')
   }
+
+  if (options.customJsonLogicOps) {
+    if (typeof options.customJsonLogicOps !== 'object' || options.customJsonLogicOps === null) {
+      throw new TypeError('validationOptions.customJsonLogicOps must be an object.')
+    }
+
+    for (const [name, func] of Object.entries(options.customJsonLogicOps)) {
+      if (typeof func !== 'function') {
+        throw new TypeError(
+          `Custom JSON Logic operator '${name}' must be a function, but received type '${typeof func}'.`,
+        )
+      }
+    }
+  }
 }
 
 export function createHeadlessForm(
@@ -273,18 +293,26 @@ export function createHeadlessForm(
   const isError = false
 
   const handleValidation = (value: SchemaValue) => {
-    const updatedSchema = calculateFinalSchema({
-      schema,
-      values: value,
-      options: options.legacyOptions,
-    })
+    const customJsonLogicOps = options?.customJsonLogicOps
+
+    try {
+      addCustomJsonLogicOperations(customJsonLogicOps)
 
-    const result = validate(value, updatedSchema, options.legacyOptions)
+      const updatedSchema = calculateFinalSchema({
+        schema,
+        values: value,
+        options: options.legacyOptions,
+      })
 
-    // Fields properties might have changed, so we need to reset the fields by updating them in place
-    updateFieldProperties(fields, updatedSchema, schema)
+      const result = validate(value, updatedSchema, options.legacyOptions)
 
-    return result
+      updateFieldProperties(fields, updatedSchema, schema)
+
+      return result
+    }
+    finally {
+      removeCustomJsonLogicOperations(customJsonLogicOps)
+    }
   }
 
   return {
diff --git a/src/validation/json-logic.ts b/src/validation/json-logic.ts
index 1530f1f8..02a28179 100644
--- a/src/validation/json-logic.ts
+++ b/src/validation/json-logic.ts
@@ -279,3 +279,19 @@ function cycleThroughAttrsAndApplyValues(propertySchema: JsfSchema, computedValu
     }
   }
 }
+
+export function addCustomJsonLogicOperations(ops?: Record<string, (...args: any[]) => any>) {
+  if (ops) {
+    for (const [name, func] of Object.entries(ops)) {
+      jsonLogic.add_operation(name, func)
+    }
+  }
+}
+
+export function removeCustomJsonLogicOperations(ops?: Record<string, (...args: any[]) => any>) {
+  if (ops) {
+    for (const name of Object.keys(ops)) {
+      jsonLogic.rm_operation(name)
+    }
+  }
+}
diff --git a/test/validation/json-logic-v0.test.js b/test/validation/json-logic-v0.test.js
index 8fdf2bbe..727e0916 100644
--- a/test/validation/json-logic-v0.test.js
+++ b/test/validation/json-logic-v0.test.js
@@ -15,6 +15,7 @@ import {
   schemaWithComputedAttributeThatDoesntExist,
   schemaWithComputedAttributeThatDoesntExistDescription,
   schemaWithComputedAttributeThatDoesntExistTitle,
+  schemaWithCustomValidationFunction,
   schemaWithDeepVarThatDoesNotExist,
   schemaWithDeepVarThatDoesNotExistOnFieldset,
   schemaWithInlinedRuleOnComputedAttributeThatReferencesUnknownVar,
@@ -446,4 +447,38 @@ describe('jsonLogic: cross-values validations', () => {
       expect(handleValidation({ field_a: 20, field_b: 41 }).formErrors).toEqual()
     })
   })
+
+  describe('custom operators', () => {
+    it('custom function', () => {
+      const { handleValidation } = createHeadlessForm(schemaWithCustomValidationFunction, { strictInputType: false, customJsonLogicOps: { is_hello: a => a === 'hello world' } })
+      expect(handleValidation({ field_a: 'hello world' }).formErrors).toEqual(undefined)
+      const { formErrors } = handleValidation({ field_a: 'wrong text' })
+      expect(formErrors?.field_a).toEqual('Invalid hello world')
+    })
+
+    it('custom function are form specific', () => {
+      const { handleValidation } = createHeadlessForm(schemaWithCustomValidationFunction, { strictInputType: false, customJsonLogicOps: { is_hello: a => a === 'hello world' } })
+      expect(handleValidation({ field_a: 'hello world' }).formErrors).toEqual(undefined)
+      const { formErrors } = handleValidation({ field_a: 'wrong text' })
+      expect(formErrors?.field_a).toEqual('Invalid hello world')
+
+      const { handleValidation: handleValidation2 } = createHeadlessForm(schemaWithCustomValidationFunction, { strictInputType: false, customJsonLogicOps: { is_hello: a => a === 'hello world!' } })
+      expect(handleValidation2({ field_a: 'hello world!' }).formErrors).toEqual(undefined)
+
+      const { handleValidation: handleValidation3 } = createHeadlessForm(schemaWithCustomValidationFunction, { strictInputType: false })
+      const actionThatWillThrow = () => {
+        handleValidation3({ field_a: 'hello world' })
+      }
+
+      expect(actionThatWillThrow).toThrow('Unrecognized operation is_hello')
+    })
+
+    it('validation on custom functions', () => {
+      const actionThatWillThrow = () => {
+        createHeadlessForm(schemaWithCustomValidationFunction, { strictInputType: false, customJsonLogicOps: { is_hello: 'not a funcion' } })
+      }
+
+      expect(actionThatWillThrow).toThrow('Custom JSON Logic operator \'is_hello\' must be a function, but received type \'string\'.')
+    })
+  })
 })
diff --git a/test/validation/json-logic.fixtures.js b/test/validation/json-logic.fixtures.js
index 4dc7d45b..15a70616 100644
--- a/test/validation/json-logic.fixtures.js
+++ b/test/validation/json-logic.fixtures.js
@@ -744,3 +744,22 @@ export const schemaWithReduceAccumulator = {
     },
   },
 }
+
+export const schemaWithCustomValidationFunction = {
+  'properties': {
+    field_a: {
+      'type': 'string',
+      'x-jsf-logic-validations': ['hello_world'],
+    },
+  },
+  'x-jsf-logic': {
+    validations: {
+      hello_world: {
+        errorMessage: 'Invalid hello world',
+        rule: {
+          is_hello: { var: 'field_a' },
+        },
+      },
+    },
+  },
+}