--- last_modified: 2026-06-25 title: "Web Platform APIs" description: "A guide to the Web Platform APIs available in Deno. Learn about fetch, events, workers, storage, and other web standard APIs, including implementation details and deviations from browser specifications." oldUrl: - /runtime/manual/runtime/navigator_api/ - /runtime/manual/runtime/web_platform_apis/ - /runtime/manual/runtime/location_api/ - /runtime/manual/runtime/web_storage_api/ - /runtime/manual/runtime/workers/ --- One way Deno simplifies web and cloud development is by using standard Web Platform APIs (like `fetch`, WebSockets and more) over proprietary APIs. This means if you've ever built for the browser, you're likely already familiar with Deno, and if you're learning Deno, you're also investing in your knowledge of the web. Explore supported Web APIs Below we'll highlight some of the standard Web APIs that Deno supports. To check if a Web Platform API is available in Deno, you can click on [the interface on MDN](https://developer.mozilla.org/en-US/docs/Web/API#interfaces) and refer to [its Browser Compatibility table](https://developer.mozilla.org/en-US/docs/Web/API/AbortController#browser_compatibility). ## fetch The [`fetch`](/api/web/~/fetch) API can be used to make HTTP requests. It is implemented as specified in the [WHATWG `fetch` spec](https://fetch.spec.whatwg.org/). ### Spec deviations - The Deno user agent does not have a cookie jar. As such, the `set-cookie` header on a response is not processed, or filtered from the visible response headers. - Deno does not follow the same-origin policy, because the Deno user agent currently does not have the concept of origins, and it does not have a cookie jar. This means Deno does not need to protect against leaking authenticated data cross origin. Because of this Deno does not implement the following sections of the WHATWG `fetch` specification: - Section `3.1. 'Origin' header`. - Section `3.2. CORS protocol`. - Section `3.5. CORB`. - Section `3.6. 'Cross-Origin-Resource-Policy' header`. - `Atomic HTTP redirect handling`. - The `opaqueredirect` response type. - A `fetch` with a `redirect` mode of `manual` will return a `basic` response rather than an `opaqueredirect` response. - The specification is vague on how [`file:` URLs are to be handled](https://fetch.spec.whatwg.org/#scheme-fetch). Firefox is the only mainstream browser that implements fetching `file:` URLs, and even then it doesn't work by default. As of Deno 1.16, Deno supports fetching local files. See the next section for details. - The `request` and `response` header guards are implemented, but unlike browsers do not have any constraints on which header names are allowed. - The `referrer`, `referrerPolicy`, `mode`, `credentials`, `cache`, `integrity`, `keepalive`, and `window` properties and their relevant behaviours in `RequestInit` are not implemented. The relevant fields are not present on the [`Request`](/api/web/~/Request) object. - The `priority` member of `RequestInit` (`"auto"`, `"high"`, or `"low"`) is accepted and validated. Following the Fetch standard it is write-only, so it is not exposed back as a property on the `Request` object. - Request body upload streaming is supported (on HTTP/1.1 and HTTP/2). Unlike the current fetch proposal, the implementation supports duplex streaming. - The `set-cookie` header is not concatenated when iterated over in the `headers` iterator. This behaviour is in the [process of being specified](https://github.com/whatwg/fetch/pull/1346). ### Fetching local files Deno supports fetching `file:` URLs. This makes it easier to write code that uses the same code path on a server as local, as well as easier to author code that works both with the Deno CLI and Deno Deploy. Deno only supports absolute file URLs, this means that `fetch("./some.json")` will not work. It should be noted though that if [`--location`](#location) is specified, relative URLs use the `--location` as the base, but a `file:` URL cannot be passed as the `--location`. To be able to fetch a resource, relative to the current module, which would work if the module is local or remote, you should to use `import.meta.url` as the base. For example: ```js const response = await fetch(new URL("./config.json", import.meta.url)); const config = await response.json(); ``` Notes on fetching local files: - Permissions are applied to reading resources, so an appropriate `--allow-read` permission is needed to be able to read a local file. - Fetching locally only supports the `GET` method, and will reject the promise with any other method. - A file that does not exist simply rejects the promise with a vague `TypeError`. This is to avoid the potential of fingerprinting attacks. - No headers are set on the response. Therefore it is up to the consumer to determine things like the content type or content length. - Response bodies are streamed from the Rust side, so large files are available in chunks, and can be cancelled. ## Structured Clone & Transferable Objects Deno supports [`structuredClone()`](/api/web/~/structuredClone) and [`postMessage()`](/api/web/~/Worker) for cloning and transferring objects across contexts (e.g. between the main thread and Web Workers). ### Serializable types These types can be cloned with `structuredClone()` and sent via `postMessage()`: | Type | Notes | | ----------------------------------------- | -------------------------------------------------------------------------------------------- | | Primitives | `string`, `number`, `boolean`, `null`, `undefined`, `bigint` | | `Array`, `Object`, `Map`, `Set` | Including nested structures and circular references | | `Date`, `RegExp` | | | `ArrayBuffer`, `TypedArray`, `DataView` | Copied by default, or transferred (see below) | | `Error` types | `Error`, `EvalError`, `RangeError`, `ReferenceError`, `SyntaxError`, `TypeError`, `URIError` | | [`Blob`](/api/web/~/Blob) | Requires Deno 2.8+ | | [`File`](/api/web/~/File) | Requires Deno 2.8+ | | [`DOMException`](/api/web/~/DOMException) | | | [`CryptoKey`](/api/web/~/CryptoKey) | | ### Transferable types These types can be _transferred_ (not copied) via the `transfer` option in `structuredClone()` or the `transfer` list in `postMessage()`. After transfer, the original object becomes unusable: | Type | Notes | | ----------------------------------------------- | ---------------------------------------- | | [`ArrayBuffer`](/api/web/~/ArrayBuffer) | Moves the backing memory to the receiver | | [`MessagePort`](/api/web/~/MessagePort) | Transfers the port to another context | | [`ReadableStream`](/api/web/~/ReadableStream) | Transfers the stream to another context | | [`WritableStream`](/api/web/~/WritableStream) | Transfers the stream to another context | | [`TransformStream`](/api/web/~/TransformStream) | Transfers the stream to another context | ```ts // Clone a Blob const blob = new Blob(["hello"], { type: "text/plain" }); const cloned = structuredClone(blob); console.log(await cloned.text()); // "hello" // Transfer an ArrayBuffer through a MessageChannel const buffer = new ArrayBuffer(1024); const ch = new MessageChannel(); ch.port1.postMessage(buffer, [buffer]); // buffer.byteLength is now 0 (transferred) ``` ## CustomEvent and EventTarget The [DOM Event API](/api/web/~/Event) can be used to dispatch and listen to events happening in an application. It is implemented as specified in the [WHATWG DOM spec](https://dom.spec.whatwg.org/#events). ### Spec deviations - Events do not bubble, because Deno does not have a DOM hierarchy, so there is no tree for Events to bubble/capture through. - `timeStamp` property is always set to `0`. ## Typings The TypeScript definitions for the implemented web APIs can be found in the [`lib.deno.shared_globals.d.ts`](https://github.com/denoland/deno/blob/main/cli/tsc/dts/lib.deno.shared_globals.d.ts) and [`lib.deno.window.d.ts`](https://github.com/denoland/deno/blob/main/cli/tsc/dts/lib.deno.window.d.ts) files. Definitions that are specific to workers can be found in the [`lib.deno.worker.d.ts`](https://github.com/denoland/deno/blob/main/cli/tsc/dts/lib.deno.worker.d.ts) file. ## Location Deno supports the [`location`](/api/web/~/Location) global from the web. ### Location flag There is no "web page" whose URL we can use for a location in a Deno process. We instead allow users to emulate a document location by specifying one on the CLI using the `--location` flag. It can be a `http` or `https` URL. ```ts // deno run --location https://example.com/path main.ts console.log(location.href); // "https://example.com/path" ``` You must pass `--location ` for this to work. If you don't, any access to the `location` global will throw an error. ```ts // deno run main.ts console.log(location.href); // error: Uncaught ReferenceError: Access to "location", run again with --location . ``` Setting `location` or any of its fields will normally cause navigation in browsers. This is not applicable in Deno, so it will throw in this situation. ```ts // deno run --location https://example.com/path main.ts location.pathname = "./foo"; // error: Uncaught NotSupportedError: Cannot set "location.pathname". ``` ### Extended usage On the web, resource resolution (excluding modules) typically uses the value of `location.href` as the root on which to base any relative URLs. This affects some web APIs adopted by Deno. #### Fetch API ```ts // deno run --location https://api.github.com/ --allow-net main.ts const response = await fetch("./orgs/denoland"); // Fetches "https://api.github.com/orgs/denoland". ``` The `fetch()` call above would throw if the `--location` flag was not passed, since there is no web-analogous location to base it onto. #### Worker modules ```ts // deno run --location https://example.com/index.html --allow-net main.ts const worker = new Worker("./workers/hello.ts", { type: "module" }); // Fetches worker module at "https://example.com/workers/hello.ts". ``` :::note For the above use cases, it is preferable to pass URLs in full rather than relying on `--location`. You can manually base a relative URL using the [`URL`](/api/web/~/URL) constructor if needed. ::: The `--location` flag is intended for those who have a specific purpose in mind for emulating a document location and are aware that this will only work at application-level. However, you may also use it to silence errors from a dependency which is frivolously accessing the `location` global. ## Web Storage The [Web Storage API](/api/web/storage) provides an API for storing string keys and values. Persisting data works similar to a browser, and has a 10MB storage limit. The global `sessionStorage` object only persists data for the current execution context, while `localStorage` persists data from execution to execution. In a browser, `localStorage` persists data uniquely per origin (effectively the protocol plus hostname plus port). As of Deno 1.16, Deno has a set of rules to determine what is a unique storage location: - When using the `--location` flag, the origin for the location is used to uniquely store the data. That means a location of `http://example.com/a.ts` and `http://example.com/b.ts` and `http://example.com:80/` would all share the same storage, but `https://example.com/` would be different. - If there is no location specifier, but there is a `--config` configuration file specified, the absolute path to that configuration file is used. That means `deno run --config deno.jsonc a.ts` and `deno run --config deno.jsonc b.ts` would share the same storage, but `deno run --config tsconfig.json a.ts` would be different. - If there is no configuration or location specifier, Deno uses the absolute path to the main module to determine what storage is shared. The Deno REPL generates a "synthetic" main module that is based off the current working directory where `deno` is started from. This means that multiple invocations of the REPL from the same path will share the persisted `localStorage` data. To set, get and remove items from `localStorage`, you can use the following: ```ts // Set an item in localStorage localStorage.setItem("myDemo", "Deno App"); // Read an item from localStorage const cat = localStorage.getItem("myDemo"); // Remove an item from localStorage localStorage.removeItem("myDemo"); // Remove all items from localStorage localStorage.clear(); ``` ## Web Workers Deno supports the [`Web Worker API`](/api/web/workers). Workers can be used to run code on multiple threads. Each instance of `Worker` is run on a separate thread, dedicated only to that worker. Currently Deno supports only `module` type workers; thus it's essential to pass the `type: "module"` option when creating a new worker. Use of relative module specifiers in the main worker are only supported with `--location ` passed on the CLI. This is not recommended for portability. You can instead use the [`URL`](/api/web/~/URL) constructor and `import.meta.url` to easily create a specifier for some nearby script. Dedicated workers, however, have a location and this capability by default. ```ts // Good new Worker(import.meta.resolve("./worker.js"), { type: "module" }); // Bad new Worker(import.meta.resolve("./worker.js")); new Worker(import.meta.resolve("./worker.js"), { type: "classic" }); new Worker("./worker.js", { type: "module" }); ``` As with regular modules, you can use top-level `await` in worker modules. However, you should be careful to always register the message handler before the first `await`, since messages can be lost otherwise. This is not a bug in Deno, it's just an unfortunate interaction of features, and it also happens in all browsers that support module workers. ```ts import { delay } from "jsr:@std/async@1/delay"; // First await: waits for a second, then continues running the module. await delay(1000); // The message handler is only set after that 1s delay, so some of the messages // that reached the worker during that second might have been fired when no // handler was registered. self.onmessage = (evt) => { console.log(evt.data); }; ``` ### Sending messages back to the main thread Communication goes both ways. The main thread sends data to the worker with `worker.postMessage()` and listens for replies with `worker.onmessage`. Inside the worker, `self.onmessage` receives messages and `self.postMessage()` sends results back: ```ts title="main.ts" const worker = new Worker(import.meta.resolve("./worker.ts"), { type: "module", }); // Receive results from the worker worker.onmessage = (evt) => { console.log("result from worker:", evt.data); }; // Send work to the worker worker.postMessage(41); ``` ```ts title="worker.ts" self.onmessage = (evt) => { const result = evt.data + 1; // Send the result back to the main thread self.postMessage(result); }; ``` Running `deno run --allow-read main.ts` prints `result from worker: 42`. ### Instantiation permissions Creating a new `Worker` instance is similar to a dynamic import; therefore Deno requires appropriate permission for this action. For workers using local modules; `--allow-read` permission is required: ```ts title="main.ts" new Worker(import.meta.resolve("./worker.ts"), { type: "module" }); ``` ```ts title="worker.ts" console.log("hello world"); self.close(); ``` ```shell $ deno run main.ts error: Uncaught PermissionDenied: read access to "./worker.ts", run again with the --allow-read flag $ deno run --allow-read main.ts hello world ``` For workers using remote modules; `--allow-net` permission is required: ```ts title="main.ts" new Worker("https://example.com/worker.ts", { type: "module" }); ``` ```ts title="worker.ts" // This file is hosted at https://example.com/worker.ts console.log("hello world"); self.close(); ``` ```shell $ deno run main.ts error: Uncaught PermissionDenied: net access to "https://example.com/worker.ts", run again with the --allow-net flag $ deno run --allow-net main.ts hello world ``` ### Using Deno in a worker ```js title="main.js" const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", }); worker.postMessage({ filename: "./log.txt" }); ``` ```js title="worker.js" self.onmessage = async (e) => { const { filename } = e.data; const text = await Deno.readTextFile(filename); console.log(text); self.close(); }; ``` ```text title="log.txt" hello world ``` ```shell $ deno run --allow-read main.js hello world ``` ### Specifying worker permissions :::caution This is an unstable Deno feature. Learn more about [unstable features](/runtime/fundamentals/stability_and_releases/#unstable-apis). ::: The permissions available for the worker are analogous to the CLI permission flags, meaning every permission enabled there can be disabled at the level of the Worker API. You can find a more detailed description of each of the permission options [here](/runtime/fundamentals/security/). By default a worker will inherit permissions from the thread it was created in, however in order to allow users to limit the access of this worker we provide the `deno.permissions` option in the worker API. For permissions that support granular access you can pass in a list of the desired resources the worker will have access to, and for those who only have the on/off option you can pass true/false respectively: ```ts const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", deno: { permissions: { net: [ "deno.land", ], read: [ new URL("./file_1.txt", import.meta.url), new URL("./file_2.txt", import.meta.url), ], write: false, }, }, }); ``` Granular access permissions receive both absolute and relative routes as arguments, however take into account that relative routes will be resolved relative to the file the worker is instantiated in, not the path the worker file is currently in: ```ts const worker = new Worker( new URL("./worker/worker.js", import.meta.url).href, { type: "module", deno: { permissions: { read: [ "/home/user/Documents/deno/worker/file_1.txt", "./worker/file_2.txt", ], }, }, }, ); ``` Both `deno.permissions` and its children support the option `"inherit"`, which implies it will borrow its parent permissions: ```ts // This worker will inherit its parent permissions const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", deno: { permissions: "inherit", }, }); ``` ```ts // This worker will inherit only the net permissions of its parent const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", deno: { permissions: { env: false, hrtime: false, net: "inherit", ffi: false, read: false, run: false, write: false, }, }, }); ``` Not specifying the `deno.permissions` option or one of its children will cause the worker to inherit by default: ```ts // This worker will inherit its parent permissions const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", }); ``` ```ts // This worker will inherit all the permissions of its parent BUT net const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", deno: { permissions: { net: false, }, }, }); ``` You can disable the permissions of the worker all together by passing `"none"` to the `deno.permissions` option: ```ts // This worker will not have any permissions enabled const worker = new Worker(import.meta.resolve("./worker.js"), { type: "module", deno: { permissions: "none", }, }); ``` ## OffscreenCanvas Starting in Deno 2.8, the [`OffscreenCanvas`](https://developer.mozilla.org/en-US/docs/Web/API/OffscreenCanvas) API is available. `OffscreenCanvas` is a canvas that lives outside any DOM and can be used anywhere (including Web Workers) for off-thread rendering and image generation. ### Supported rendering contexts `OffscreenCanvas#getContext` accepts two of the spec-defined context ids: - `"bitmaprenderer"`: returns an [`ImageBitmapRenderingContext`](https://developer.mozilla.org/en-US/docs/Web/API/ImageBitmapRenderingContext) for displaying an `ImageBitmap` produced via `createImageBitmap`. - `"webgpu"`: returns a [`GPUCanvasContext`](https://developer.mozilla.org/en-US/docs/Web/API/GPUCanvasContext) for rendering with WebGPU. Calling `getContext` with `"2d"`, `"webgl"`, or `"webgl2"` returns `null`; these contexts are not implemented in Deno. ### Example: encoding an image to PNG Decode an image into an `ImageBitmap`, place it on an `OffscreenCanvas` via the `bitmaprenderer` context, and write the result to disk: ```ts const data = await Deno.readFile("./input.jpg"); const bitmap = await createImageBitmap(new Blob([data])); const canvas = new OffscreenCanvas(bitmap.width, bitmap.height); const ctx = canvas.getContext("bitmaprenderer")!; ctx.transferFromImageBitmap(bitmap); const blob = await canvas.convertToBlob({ type: "image/png" }); await Deno.writeFile( "./output.png", new Uint8Array(await blob.arrayBuffer()), ); ``` Typical uses: - producing thumbnails, format conversions, or social-card images at request time without spinning up a headless browser, - running off-thread image work inside a Web Worker, - driving WebGPU rendering targets that don't need a window. ## Geometry Interfaces Starting in Deno 2.8, the [Geometry Interfaces Module Level 1](https://drafts.fxtf.org/geometry/) types are available as globals. These are the same types you'd find in a browser: - [`DOMMatrix`](https://developer.mozilla.org/en-US/docs/Web/API/DOMMatrix) / [`DOMMatrixReadOnly`](https://developer.mozilla.org/en-US/docs/Web/API/DOMMatrixReadOnly): 4×4 transform matrices for 2D and 3D operations. - [`DOMPoint`](https://developer.mozilla.org/en-US/docs/Web/API/DOMPoint) / [`DOMPointReadOnly`](https://developer.mozilla.org/en-US/docs/Web/API/DOMPointReadOnly): points in 2D / 3D space. - [`DOMRect`](https://developer.mozilla.org/en-US/docs/Web/API/DOMRect) / [`DOMRectReadOnly`](https://developer.mozilla.org/en-US/docs/Web/API/DOMRectReadOnly): axis-aligned rectangles. - [`DOMQuad`](https://developer.mozilla.org/en-US/docs/Web/API/DOMQuad): a quadrilateral defined by four points. ```ts const m = new DOMMatrix().translateSelf(10, 20).scaleSelf(2); const p = new DOMPoint(1, 1).matrixTransform(m); console.log(p.x, p.y); // 12 22 ``` These types are useful for graphics work; applying transforms to canvas drawings, computing layout math, or porting browser code that depends on geometry types. ## navigator Deno implements a subset of the [`navigator`](https://developer.mozilla.org/en-US/docs/Web/API/Navigator) global. The following properties are available: - `navigator.userAgent` — always `"Deno/"` - `navigator.platform` — the underlying OS platform (e.g. `"Linux x86_64"`, `"MacIntel"`, `"Win32"`). Added in Deno 2.7. - `navigator.hardwareConcurrency` — number of logical CPU cores - `navigator.userAgentData` — a [`NavigatorUAData`](https://developer.mozilla.org/en-US/docs/Web/API/NavigatorUAData) object implementing the User-Agent Client Hints API. The low-entropy properties `brands`, `mobile`, and `platform` are read synchronously, while `getHighEntropyValues(hints)` resolves with additional details such as `architecture`, `model`, and `platformVersion`. - `navigator.locks` — a [`LockManager`](https://developer.mozilla.org/en-US/docs/Web/API/LockManager) implementing the [Web Locks API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Locks_API), for coordinating access to a named resource with `navigator.locks.request()` and `navigator.locks.query()`. ```ts console.log(navigator.userAgent); // "Deno/2.7.0" console.log(navigator.platform); // e.g. "Linux x86_64", "MacIntel", "Win32" console.log(navigator.hardwareConcurrency); // e.g. 8 console.log(navigator.userAgentData.brands); // e.g. [{ brand: "Deno", version: "2" }] ``` ## Temporal The [Temporal API](https://tc39.es/proposal-temporal/docs/) is a modern date/time library that replaces `Date` for most use cases. It was stabilized in Deno 2.7 and is available as a global without any flags. ```ts // Current date/time in local timezone const now = Temporal.Now.plainDateTimeISO(); console.log(now.toString()); // e.g. "2025-03-12T10:30:00" // Parse a date const date = Temporal.PlainDate.from("2025-03-12"); console.log(date.month); // 3 // Timezone-aware const zonedNow = Temporal.Now.zonedDateTimeISO("America/New_York"); console.log(zonedNow.timeZoneId); // "America/New_York" ``` Prior to Deno 2.7, Temporal required the `--unstable-temporal` flag. ## CompressionStream and DecompressionStream Deno supports [`CompressionStream`](https://developer.mozilla.org/en-US/docs/Web/API/CompressionStream) and [`DecompressionStream`](https://developer.mozilla.org/en-US/docs/Web/API/DecompressionStream) for streaming compression and decompression. ### Supported formats | Format | String | Notes | | ----------- | --------------- | ------------------ | | gzip | `"gzip"` | RFC 1952 | | deflate | `"deflate"` | zlib (RFC 1950) | | deflate-raw | `"deflate-raw"` | raw DEFLATE (1951) | | Brotli | `"brotli"` | Added in Deno 2.7 | ```ts // Compress with Brotli const input = new TextEncoder().encode("Hello, Deno!"); const cs = new CompressionStream("brotli"); const writer = cs.writable.getWriter(); writer.write(input); writer.close(); const compressed = await new Response(cs.readable).arrayBuffer(); // Decompress const ds = new DecompressionStream("brotli"); const writer2 = ds.writable.getWriter(); writer2.write(new Uint8Array(compressed)); writer2.close(); const result = await new Response(ds.readable).text(); console.log(result); // "Hello, Deno!" ``` ## Web Crypto Deno supports the [Web Crypto API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Crypto_API) via `crypto.subtle`. ### Feature detection `SubtleCrypto.supports()` is a static method for synchronously checking whether a given algorithm and operation combination is available, without running the operation or catching an error. It takes the operation name, the algorithm, and an optional third argument, and returns a boolean. Added in Deno 2.9. ```ts SubtleCrypto.supports("digest", "SHA3-256"); // true SubtleCrypto.supports("generateKey", "ChaCha20-Poly1305"); // true SubtleCrypto.supports("sign", "ML-DSA-65"); // true ``` The operation is one of `"encrypt"`, `"decrypt"`, `"sign"`, `"verify"`, `"digest"`, `"generateKey"`, `"deriveKey"`, `"deriveBits"`, `"importKey"`, `"exportKey"`, `"wrapKey"`, `"unwrapKey"`, `"encapsulateKey"`, `"encapsulateBits"`, `"decapsulateKey"`, `"decapsulateBits"`, or `"getPublicKey"`. The optional third argument is interpreted by operation: a length in bits for `"deriveBits"`, and a related algorithm otherwise, such as the derived-key algorithm for `"deriveKey"` or the shared-key algorithm for `"encapsulateKey"` and `"decapsulateKey"`. ```ts // Will deriveKey produce an AES-GCM key from HKDF? SubtleCrypto.supports("deriveKey", "HKDF", { name: "AES-GCM", length: 256 }); ``` `SubtleCrypto.supports()` is part of the WICG [Modern Algorithms in the Web Cryptography API](https://wicg.github.io/webcrypto-modern-algos/) draft. ### SHA-3 hash algorithms Starting with Deno 2.7, the SHA-3 family of hash algorithms is supported by `crypto.subtle.digest`: - `SHA3-256` - `SHA3-384` - `SHA3-512` ```ts const data = new TextEncoder().encode("Hello, Deno!"); const hash = await crypto.subtle.digest("SHA3-256", data); console.log(new Uint8Array(hash)); ``` An `HMAC` key can also use a SHA-3 hash. Pass the algorithm name as the `hash` when you generate or import the key: ```ts const key = await crypto.subtle.generateKey( { name: "HMAC", hash: "SHA3-256" }, true, ["sign", "verify"], ); const signature = await crypto.subtle.sign("HMAC", key, data); ``` ### Extendable-output functions Deno 2.9 adds the SHAKE, cSHAKE, TurboSHAKE, and KangarooTwelve extendable-output functions (XOFs). Unlike a fixed-size hash, an XOF can produce a digest of any length, so `crypto.subtle.digest` requires an `outputLength` option giving the output size in bits. `outputLength` must be a positive multiple of 8. The supported names are: - `SHAKE128`, `SHAKE256` - `cSHAKE128`, `cSHAKE256` - `TurboSHAKE128`, `TurboSHAKE256` - `KT128` (also accepted as `KangarooTwelve`) and `KT256` ```ts const data = new TextEncoder().encode("Hello, Deno!"); // 256-bit (32-byte) SHAKE256 digest. const digest = await crypto.subtle.digest( { name: "SHAKE256", outputLength: 256 }, data, ); console.log(new Uint8Array(digest).length); // 32 ``` `cSHAKE128` and `cSHAKE256` accept two optional `BufferSource` parameters that customize the function: `functionName`, a NIST-defined function name, and `customization`, a caller-defined domain separation string. ```ts const digest = await crypto.subtle.digest( { name: "cSHAKE128", outputLength: 256, customization: new TextEncoder().encode("my-app"), }, data, ); ``` `TurboSHAKE128` and `TurboSHAKE256` accept an optional `domainSeparation` byte, which must be in the range `0x01` to `0x7F`: ```ts const digest = await crypto.subtle.digest( { name: "TurboSHAKE256", outputLength: 512, domainSeparation: 0x1f }, data, ); ``` `KT128` and `KT256` are KangarooTwelve XOFs. They accept an optional `customization` `BufferSource`: ```ts const digest = await crypto.subtle.digest( { name: "KT128", outputLength: 256 }, data, ); ``` ### KMAC `KMAC128` and `KMAC256` are keyed message authentication codes built on cSHAKE. Added in Deno 2.9. Generate a key with a `length` in bits, then sign and verify with an `outputLength` in bits and an optional `customization` `BufferSource`: ```ts const key = await crypto.subtle.generateKey( { name: "KMAC128", length: 128 }, true, ["sign", "verify"], ); const data = new TextEncoder().encode("Hello, Deno!"); const params = { name: "KMAC128", outputLength: 256, customization: new TextEncoder().encode("Deno"), }; const mac = await crypto.subtle.sign(params, key, data); const valid = await crypto.subtle.verify(params, key, mac, data); ``` KMAC keys can be imported and exported in the `"raw"`, `"raw-secret"`, and `"jwk"` formats. ### Argon2 `Argon2d`, `Argon2i`, and `Argon2id` are password-hashing key-derivation functions. Added in Deno 2.9. Import the password as a key in the `"raw-secret"` format with the `deriveBits` usage, then call `deriveBits`. The parameters are `memory` (memory cost in kibibytes), `passes` (iterations), `parallelism` (degree of parallelism), and a `nonce` `BufferSource` (the salt). `secretValue` and `associatedData` are optional `BufferSource` values: ```ts const password = new TextEncoder().encode("correct horse battery staple"); const key = await crypto.subtle.importKey( "raw-secret", password, "Argon2id", false, ["deriveBits"], ); const derived = await crypto.subtle.deriveBits( { name: "Argon2id", memory: 65536, passes: 3, parallelism: 4, nonce: crypto.getRandomValues(new Uint8Array(16)), }, key, 256, // output length in bits ); ``` ### ChaCha20-Poly1305 Deno 2.9 supports the `ChaCha20-Poly1305` authenticated encryption algorithm through `generateKey`, `encrypt`, and `decrypt`. Keys are always 256 bits: ```ts const key = await crypto.subtle.generateKey( { name: "ChaCha20-Poly1305" }, true, ["encrypt", "decrypt"], ); ``` Each `encrypt` and `decrypt` call takes a 12-byte `nonce` and optional `additionalData` that is authenticated but not encrypted. Use a fresh nonce for every message encrypted under the same key: ```ts const nonce = crypto.getRandomValues(new Uint8Array(12)); const data = new TextEncoder().encode("Hello, Deno!"); const ciphertext = await crypto.subtle.encrypt( { name: "ChaCha20-Poly1305", nonce }, key, data, ); const plaintext = await crypto.subtle.decrypt( { name: "ChaCha20-Poly1305", nonce }, key, ciphertext, ); console.log(new TextDecoder().decode(plaintext)); // "Hello, Deno!" ``` The returned ciphertext includes the 16-byte Poly1305 authentication tag. ### Post-quantum cryptography Deno 2.9 implements the NIST post-quantum algorithms from the WICG [Modern Algorithms in the Web Cryptography API](https://wicg.github.io/webcrypto-modern-algos/) draft: ML-DSA and SLH-DSA signatures, and ML-KEM key encapsulation. #### ML-DSA signatures `ML-DSA` (FIPS 204) is a lattice-based digital signature scheme. Three parameter sets are available, in increasing security level: `ML-DSA-44`, `ML-DSA-65`, and `ML-DSA-87`. Generate a key pair, then sign with the private key and verify with the public key: ```ts const { publicKey, privateKey } = await crypto.subtle.generateKey( { name: "ML-DSA-65" }, true, ["sign", "verify"], ); const data = new TextEncoder().encode("Hello, Deno!"); const signature = await crypto.subtle.sign( { name: "ML-DSA-65" }, privateKey, data, ); const valid = await crypto.subtle.verify( { name: "ML-DSA-65" }, publicKey, signature, data, ); console.log(valid); // true ``` `sign` and `verify` accept an optional `context`, a `BufferSource` that binds the signature to an application-specific value. The same `context` must be supplied to both calls: ```ts const context = new TextEncoder().encode("v1"); const signature = await crypto.subtle.sign( { name: "ML-DSA-65", context }, privateKey, data, ); ``` ML-DSA keys can be imported and exported in the `"pkcs8"`, `"spki"`, `"jwk"`, `"raw-public"`, `"raw-private"`, and `"raw-seed"` formats. #### SLH-DSA signatures `SLH-DSA` (FIPS 205) is a stateless hash-based signature scheme. All twelve parameter sets are available, combining a hash family (`SHA2` or `SHAKE`), a security level (`128`, `192`, or `256`), and a `s` (small signature) or `f` (fast) tradeoff: - `SLH-DSA-SHA2-128s`, `SLH-DSA-SHA2-128f`, `SLH-DSA-SHA2-192s`, `SLH-DSA-SHA2-192f`, `SLH-DSA-SHA2-256s`, `SLH-DSA-SHA2-256f` - `SLH-DSA-SHAKE-128s`, `SLH-DSA-SHAKE-128f`, `SLH-DSA-SHAKE-192s`, `SLH-DSA-SHAKE-192f`, `SLH-DSA-SHAKE-256s`, `SLH-DSA-SHAKE-256f` SLH-DSA uses the same `generateKey`, `sign`, and `verify` flow as ML-DSA, including the optional `context`: ```ts const { publicKey, privateKey } = await crypto.subtle.generateKey( { name: "SLH-DSA-SHAKE-128f" }, true, ["sign", "verify"], ); const data = new TextEncoder().encode("Hello, Deno!"); const signature = await crypto.subtle.sign( { name: "SLH-DSA-SHAKE-128f" }, privateKey, data, ); ``` SLH-DSA keys can be imported and exported in the `"pkcs8"`, `"spki"`, `"jwk"`, `"raw-public"`, and `"raw-private"` formats. #### ML-KEM key encapsulation `ML-KEM` (FIPS 203) is a key-encapsulation mechanism: one party encapsulates a fresh shared secret to a recipient's public key, and the recipient decapsulates the resulting ciphertext to recover the same secret. The parameter sets are `ML-KEM-512`, `ML-KEM-768`, and `ML-KEM-1024`. The recipient generates a key pair and publishes the public (encapsulation) key. The sender calls `encapsulateKey`, which returns both the `ciphertext` to send back and a `sharedKey` `CryptoKey` for the algorithm named by its third argument. The recipient passes the ciphertext to `decapsulateKey` to derive the same key: ```ts const { publicKey, privateKey } = await crypto.subtle.generateKey( { name: "ML-KEM-768" }, true, ["encapsulateKey", "decapsulateKey"], ); // Sender: encapsulate a shared AES-GCM key to the recipient's public key. const { ciphertext, sharedKey } = await crypto.subtle.encapsulateKey( { name: "ML-KEM-768" }, publicKey, { name: "AES-GCM", length: 256 }, false, ["encrypt", "decrypt"], ); // Recipient: decapsulate the ciphertext to recover the same key. const recovered = await crypto.subtle.decapsulateKey( { name: "ML-KEM-768" }, privateKey, ciphertext, { name: "AES-GCM", length: 256 }, false, ["encrypt", "decrypt"], ); ``` `encapsulateBits` and `decapsulateBits` are the lower-level variants: they return the raw shared secret as an `ArrayBuffer` instead of importing it as a `CryptoKey`. A decapsulation (private) key also exposes `getPublicKey()`, which returns its matching encapsulation (public) key. ## createImageBitmap Deno supports [`createImageBitmap()`](https://developer.mozilla.org/en-US/docs/Web/API/createImageBitmap) for decoding images into `ImageBitmap` objects that can be used with [`OffscreenCanvas`](#offscreencanvas). ### Supported input formats | Format | Notes | | ------ | ----------------- | | PNG | | | JPEG | | | BMP | | | GIF | Added in Deno 2.7 | | WebP | Added in Deno 2.7 | ```ts const data = await Deno.readFile("./image.gif"); const bitmap = await createImageBitmap(new Blob([data])); console.log(bitmap.width, bitmap.height); ``` ## File locking [`Deno.FsFile`](/api/deno/~/Deno.FsFile) supports advisory file locking to coordinate access between processes: - [`lock(exclusive?)`](/api/deno/~/Deno.FsFile.prototype.lock) — acquires a lock. Shared (read) by default; pass `true` for exclusive (write). Blocks if an incompatible lock is held. - [`lockSync(exclusive?)`](/api/deno/~/Deno.FsFile.prototype.lockSync) — synchronous variant of `lock()`. - [`tryLock(exclusive?)`](/api/deno/~/Deno.FsFile.prototype.tryLock) — non-blocking. Returns `true` if the lock was acquired, `false` otherwise. Added in Deno 2.7. - [`tryLockSync(exclusive?)`](/api/deno/~/Deno.FsFile.prototype.tryLockSync) — synchronous variant of `tryLock()`. ```ts const file = await Deno.open("./data.txt", { read: true, write: true }); const locked = await file.tryLock(true); // exclusive if (locked) { await file.write(new TextEncoder().encode("hello")); await file.unlock(); } else { console.log("File is locked by another process, skipping."); } file.close(); ``` ## Deviations of other APIs from spec ### Cache API Only the following APIs are implemented: - [CacheStorage::open()](https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage/open) - [CacheStorage::has()](https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage/has) - [CacheStorage::delete()](https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage/delete) - [CacheStorage::keys()](https://developer.mozilla.org/en-US/docs/Web/API/CacheStorage/keys) (Deno 2.8+) - [Cache::match()](https://developer.mozilla.org/en-US/docs/Web/API/Cache/match) - [Cache::put()](https://developer.mozilla.org/en-US/docs/Web/API/Cache/put) - [Cache::delete()](https://developer.mozilla.org/en-US/docs/Web/API/Cache/delete) - [Cache::keys()](https://developer.mozilla.org/en-US/docs/Web/API/Cache/keys) (Deno 2.8+) A few things that are different compared to browsers: 1. You cannot pass relative paths to the APIs. The request can be an instance of Request or URL or a url string. 2. `match()` & `delete()` don't support query options yet.