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title: Edge Runtime |
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description: API Reference for the Edge Runtime. |
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--- |
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{/* The content of this doc is shared between the app and pages router. You can use the `<PagesOnly>Content</PagesOnly>` component to add content that is specific to the Pages Router. Any shared content should not be wrapped in a component. */} |
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Next.js has two server runtimes you can use in your application: |
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- The **Node.js Runtime** (default), which has access to all Node.js APIs and is used for rendering your application. |
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- The **Edge Runtime** which contains a more limited [set of APIs]( |
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- The Edge Runtime does not support all Node.js APIs. Some packages may not work as expected. |
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- The Edge Runtime does not support Incremental Static Regeneration (ISR). |
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- Both runtimes can support [streaming](/docs/app/api-reference/file-conventions/loading) depending on your deployment adapter. |
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The Edge Runtime supports the following APIs: |
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| API | Description | |
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| ------------------------------------------------------------------------------- | --------------------------------- | |
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| [`Blob`](https://developer.mozilla.org/docs/Web/API/Blob) | Represents a blob | |
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| [`fetch`](https://developer.mozilla.org/docs/Web/API/Fetch_API) | Fetches a resource | |
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| [`FetchEvent`](https://developer.mozilla.org/docs/Web/API/FetchEvent) | Represents a fetch event | |
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| [`File`](https://developer.mozilla.org/docs/Web/API/File) | Represents a file | |
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| [`FormData`](https://developer.mozilla.org/docs/Web/API/FormData) | Represents form data | |
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| [`Headers`](https://developer.mozilla.org/docs/Web/API/Headers) | Represents HTTP headers | |
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| [`Request`](https://developer.mozilla.org/docs/Web/API/Request) | Represents an HTTP request | |
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| [`Response`](https://developer.mozilla.org/docs/Web/API/Response) | Represents an HTTP response | |
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| [`URLSearchParams`](https://developer.mozilla.org/docs/Web/API/URLSearchParams) | Represents URL search parameters | |
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| [`WebSocket`](https://developer.mozilla.org/docs/Web/API/WebSocket) | Represents a websocket connection | |
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| API | Description | |
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| ----------------------------------------------------------------------------------- | ---------------------------------- | |
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| [`atob`](https://developer.mozilla.org/en-US/docs/Web/API/atob) | Decodes a base-64 encoded string | |
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| [`btoa`](https://developer.mozilla.org/en-US/docs/Web/API/btoa) | Encodes a string in base-64 | |
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| [`TextDecoder`](https://developer.mozilla.org/docs/Web/API/TextDecoder) | Decodes a Uint8Array into a string | |
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| [`TextDecoderStream`](https://developer.mozilla.org/docs/Web/API/TextDecoderStream) | Chainable decoder for streams | |
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| [`TextEncoder`](https://developer.mozilla.org/docs/Web/API/TextEncoder) | Encodes a string into a Uint8Array | |
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| [`TextEncoderStream`](https://developer.mozilla.org/docs/Web/API/TextEncoderStream) | Chainable encoder for streams | |
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| API | Description | |
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| ------------------------------------------------------------------------------------------------------- | --------------------------------------- | |
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| [`ReadableStream`](https://developer.mozilla.org/docs/Web/API/ReadableStream) | Represents a readable stream | |
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| [`ReadableStreamBYOBReader`](https://developer.mozilla.org/docs/Web/API/ReadableStreamBYOBReader) | Represents a reader of a ReadableStream | |
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| [`ReadableStreamDefaultReader`](https://developer.mozilla.org/docs/Web/API/ReadableStreamDefaultReader) | Represents a reader of a ReadableStream | |
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| [`TransformStream`](https://developer.mozilla.org/docs/Web/API/TransformStream) | Represents a transform stream | |
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| [`WritableStream`](https://developer.mozilla.org/docs/Web/API/WritableStream) | Represents a writable stream | |
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| [`WritableStreamDefaultWriter`](https://developer.mozilla.org/docs/Web/API/WritableStreamDefaultWriter) | Represents a writer of a WritableStream | |
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| API | Description | |
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| ------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------- | |
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| [`crypto`](https://developer.mozilla.org/docs/Web/API/Window/crypto) | Provides access to the cryptographic functionality of the platform | |
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| [`CryptoKey`](https://developer.mozilla.org/docs/Web/API/CryptoKey) | Represents a cryptographic key | |
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| [`SubtleCrypto`](https://developer.mozilla.org/docs/Web/API/SubtleCrypto) | Provides access to common cryptographic primitives, like hashing, signing, encryption or decryption | |
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| API | Description | |
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| --------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | |
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| [`AbortController`](https://developer.mozilla.org/docs/Web/API/AbortController) | Allows you to abort one or more DOM requests as and when desired | |
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| [`Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Array) | Represents an array of values | |
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| [`ArrayBuffer`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer) | Represents a generic, fixed-length raw binary data buffer | |
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| [`Atomics`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Atomics) | Provides atomic operations as static methods | |
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| [`BigInt`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/BigInt) | Represents a whole number with arbitrary precision | |
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| [`BigInt64Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/BigInt64Array) | Represents a typed array of 64-bit signed integers | |
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| [`BigUint64Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/BigUint64Array) | Represents a typed array of 64-bit unsigned integers | |
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| [`Boolean`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Boolean) | Represents a logical entity and can have two values: `true` and `false` | |
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| [`clearInterval`](https://developer.mozilla.org/docs/Web/API/WindowOrWorkerGlobalScope/clearInterval) | Cancels a timed, repeating action which was previously established by a call to `setInterval()` | |
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| [`clearTimeout`](https://developer.mozilla.org/docs/Web/API/WindowOrWorkerGlobalScope/clearTimeout) | Cancels a timed, repeating action which was previously established by a call to `setTimeout()` | |
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| [`console`](https://developer.mozilla.org/docs/Web/API/Console) | Provides access to the browser's debugging console | |
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| [`DataView`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/DataView) | Represents a generic view of an `ArrayBuffer` | |
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| [`Date`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Date) | Represents a single moment in time in a platform-independent format | |
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| [`decodeURI`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/decodeURI) | Decodes a Uniform Resource Identifier (URI) previously created by `encodeURI` or by a similar routine | |
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| [`decodeURIComponent`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/decodeURIComponent) | Decodes a Uniform Resource Identifier (URI) component previously created by `encodeURIComponent` or by a similar routine | |
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| [`DOMException`](https://developer.mozilla.org/docs/Web/API/DOMException) | Represents an error that occurs in the DOM | |
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| [`encodeURI`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/encodeURI) | Encodes a Uniform Resource Identifier (URI) by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character | |
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| [`encodeURIComponent`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/encodeURIComponent) | Encodes a Uniform Resource Identifier (URI) component by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character | |
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| [`Error`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error) | Represents an error when trying to execute a statement or accessing a property | |
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| [`EvalError`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/EvalError) | Represents an error that occurs regarding the global function `eval()` | |
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| [`Float32Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Float32Array) | Represents a typed array of 32-bit floating point numbers | |
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| [`Float64Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Float64Array) | Represents a typed array of 64-bit floating point numbers | |
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| [`Function`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Function) | Represents a function | |
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| [`Infinity`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Infinity) | Represents the mathematical Infinity value | |
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| [`Int8Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Int8Array) | Represents a typed array of 8-bit signed integers | |
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| [`Int16Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Int16Array) | Represents a typed array of 16-bit signed integers | |
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| [`Int32Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Int32Array) | Represents a typed array of 32-bit signed integers | |
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| [`Intl`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Intl) | Provides access to internationalization and localization functionality | |
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| [`isFinite`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/isFinite) | Determines whether a value is a finite number | |
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| [`isNaN`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/isNaN) | Determines whether a value is `NaN` or not | |
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| [`JSON`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/JSON) | Provides functionality to convert JavaScript values to and from the JSON format | |
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| [`Map`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Map) | Represents a collection of values, where each value may occur only once | |
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| [`Math`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Math) | Provides access to mathematical functions and constants | |
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| [`Number`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Number) | Represents a numeric value | |
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| [`Object`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object) | Represents the object that is the base of all JavaScript objects | |
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| [`parseFloat`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/parseFloat) | Parses a string argument and returns a floating point number | |
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| [`parseInt`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/parseInt) | Parses a string argument and returns an integer of the specified radix | |
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| [`Promise`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Promise) | Represents the eventual completion (or failure) of an asynchronous operation, and its resulting value | |
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| [`Proxy`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Proxy) | Represents an object that is used to define custom behavior for fundamental operations (e.g. property lookup, assignment, enumeration, function invocation, etc) | |
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| [`queueMicrotask`](https://developer.mozilla.org/docs/Web/API/queueMicrotask) | Queues a microtask to be executed | |
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| [`RangeError`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/RangeError) | Represents an error when a value is not in the set or range of allowed values | |
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| [`ReferenceError`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/ReferenceError) | Represents an error when a non-existent variable is referenced | |
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| [`Reflect`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Reflect) | Provides methods for interceptable JavaScript operations | |
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| [`RegExp`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/RegExp) | Represents a regular expression, allowing you to match combinations of characters | |
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| [`Set`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Set) | Represents a collection of values, where each value may occur only once | |
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| [`setInterval`](https://developer.mozilla.org/docs/Web/API/setInterval) | Repeatedly calls a function, with a fixed time delay between each call | |
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| [`setTimeout`](https://developer.mozilla.org/docs/Web/API/setTimeout) | Calls a function or evaluates an expression after a specified number of milliseconds | |
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| [`SharedArrayBuffer`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/SharedArrayBuffer) | Represents a generic, fixed-length raw binary data buffer | |
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| [`String`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) | Represents a sequence of characters | |
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| [`structuredClone`](https://developer.mozilla.org/docs/Web/API/Web_Workers_API/Structured_clone_algorithm) | Creates a deep copy of a value | |
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| [`Symbol`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Symbol) | Represents a unique and immutable data type that is used as the key of an object property | |
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| [`SyntaxError`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/SyntaxError) | Represents an error when trying to interpret syntactically invalid code | |
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| [`TypeError`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/TypeError) | Represents an error when a value is not of the expected type | |
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| [`Uint8Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Uint8Array) | Represents a typed array of 8-bit unsigned integers | |
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| [`Uint8ClampedArray`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Uint8ClampedArray) | Represents a typed array of 8-bit unsigned integers clamped to 0-255 | |
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| [`Uint32Array`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Uint32Array) | Represents a typed array of 32-bit unsigned integers | |
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| [`URIError`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/URIError) | Represents an error when a global URI handling function was used in a wrong way | |
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| [`URL`](https://developer.mozilla.org/docs/Web/API/URL) | Represents an object providing static methods used for creating object URLs | |
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| [`URLPattern`](https://developer.mozilla.org/docs/Web/API/URLPattern) | Represents a URL pattern | |
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| [`URLSearchParams`](https://developer.mozilla.org/docs/Web/API/URLSearchParams) | Represents a collection of key/value pairs | |
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| [`WeakMap`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/WeakMap) | Represents a collection of key/value pairs in which the keys are weakly referenced | |
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| [`WeakSet`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/WeakSet) | Represents a collection of objects in which each object may occur only once | |
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| [`WebAssembly`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly) | Provides access to WebAssembly | |
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### Next.js Specific Polyfills |
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- [`AsyncLocalStorage`](https://nodejs.org/api/async_context.html#class-asynclocalstorage) |
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### Environment Variables |
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You can use `process.env` to access [Environment Variables](/docs/app/guides/environment-variables) for both `next dev` and `next build`. |
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### Unsupported APIs |
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The Edge Runtime has some restrictions including: |
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- Native Node.js APIs **are not supported**. For example, you can't read or write to the filesystem. |
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- `node_modules` _can_ be used, as long as they implement ES Modules and do not use native Node.js APIs. |
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- Calling `require` directly is **not allowed**. Use ES Modules instead. |
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The following JavaScript language features are disabled, and **will not work:** |
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| API | Description | |
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| ------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------- | |
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| [`eval`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/eval) | Evaluates JavaScript code represented as a string | |
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| [`new Function(evalString)`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Function) | Creates a new function with the code provided as an argument | |
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| [`WebAssembly.compile`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/compile) | Compiles a WebAssembly module from a buffer source | |
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| [`WebAssembly.instantiate`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/instantiate) | Compiles and instantiates a WebAssembly module from a buffer source | |
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In rare cases, your code could contain (or import) some dynamic code evaluation statements which _can not be reached at runtime_ and which can not be removed by treeshaking. |
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You can relax the check to allow specific files with your Middleware configuration: |
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```javascript filename="middleware.ts" |
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export const config = { |
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unstable_allowDynamic: [ |
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// allows a single file |
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'/lib/utilities.js', |
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// use a glob to allow anything in the function-bind 3rd party module |
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'**/node_modules/function-bind/**', |
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], |
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} |
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``` |
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`unstable_allowDynamic` is a [glob](https://github.com/micromatch/micromatch |
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Be warned that if these statements are executed on the Edge, _they will throw and cause a runtime error_. |
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