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