Web/API/SubtleCrypto/digest

Secure contextThis feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The digest() method of the SubtleCrypto interface generates a digest of the given data. A digest is a short fixed-length value derived from some variable-length input. Cryptographic digests should exhibit collision-resistance, meaning that it's hard to come up with two different inputs that have the same digest value.

It takes as its arguments an identifier for the digest algorithm to use and the data to digest. It returns a Promise which will be fulfilled with the digest.

Syntax

const digest = crypto.subtle.digest(algorithm, data);

Parameters

algorithm is a DOMString defining the hash function to use. Supported values are:
- SHA-1 (but don't use this in cryptographic applications)
- SHA-256
- SHA-384
- SHA-512.
data is an ArrayBuffer or ArrayBufferView containing the data to be digested.

Return value

digest is a Promise that fulfills with an ArrayBuffer containing the digest.

Supported algorithms

Digest algorithms, also known as cryptographic hash functions, transform an arbitrarily large block of data into a fixed-size output, usually much shorter than the input. They have a variety of applications in cryptography.

SHA-1

This algorithm is specified in FIPS 180-4, section 6.1, and produces an output 160 bits long.

Warning: This algorithm is now considered vulnerable and should not be used for cryptographic applications.

SHA-256

This algorithm is specified in FIPS 180-4, section 6.2, and produces an output 256 bits long.

SHA-384

This algorithm is specified in FIPS 180-4, section 6.5, and produces an output 384 bits long.

SHA-512

This algorithm is specified in FIPS 180-4, section 6.4, and produces an output 512 bits long.

Hint: If you are looking here for how to create an keyed-hash message authentication code (HMAC), you need to use the SubtleCrypto.sign() instead.

Examples

Basic example

This example encodes a message, then calculates its SHA-256 digest and logs the digest length:

const text = 'An obscure body in the S-K System, your majesty. The inhabitants refer to it as the planet Earth.';

async function digestMessage(message) {
  const encoder = new TextEncoder();
  const data = encoder.encode(message);
  const hash = await crypto.subtle.digest('SHA-256', data);
  return hash;
}

const digestBuffer = await digestMessage(text);
console.log(digestBuffer.byteLength);

Converting a digest to a hex string

The digest is returned as an ArrayBuffer, but for comparison and display digests are often represented as hex strings. This example calculates a digest, then converts the ArrayBuffer to a hex string:

const text = 'An obscure body in the S-K System, your majesty. The inhabitants refer to it as the planet Earth.';

async function digestMessage(message) {
  const msgUint8 = new TextEncoder().encode(message);                           // encode as (utf-8) Uint8Array
  const hashBuffer = await crypto.subtle.digest('SHA-256', msgUint8);           // hash the message
  const hashArray = Array.from(new Uint8Array(hashBuffer));                     // convert buffer to byte array
  const hashHex = hashArray.map(b => b.toString(16).padStart(2, '0')).join(''); // convert bytes to hex string
  return hashHex;
}

const digestHex = await digestMessage(text);
console.log(digestHex);

Specifications

Specification	Status	Comment
Web Cryptography APIThe definition of 'SubtleCrypto.digest()' in that specification.	Recommendation	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`digest`	Chrome Full support 37	Edge Partial support 12 Notes' Partial support 12 Notes' Notes' Not supported: SHA-1.	Firefox Full support 34 Full support 34 No support 32 — 34 Disabled' Disabled' From version 32 until version 34 (exclusive): this feature is behind the `dom.webcrypto.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE Partial support 11 Notes' Partial support 11 Notes' Notes' Returns `CryptoOperation` instead of `Promise`	Opera Full support 24	Safari Full support 7	WebView Android Full support 37	Chrome Android Full support 37	Firefox Android Full support 34 Full support 34 No support 32 — 34 Disabled' Disabled' From version 32 until version 34 (exclusive): this feature is behind the `dom.webcrypto.enabled` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android Full support 24	Safari iOS Full support 7	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
Partial support: Partial support
See implementation notes.': See implementation notes.
User must explicitly enable this feature.': User must explicitly enable this feature.

In Chrome 60, they added a feature that disables crypto.subtle for non-TLS connections.