SubtleCrypto: digest() method
=============================

**Secure context:** This 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.

Note that this API does not support streaming input: you must read the entire input into memory before passing it into the digest function.

Syntax
------


```js
digest(algorithm, data)
```

### Parameters

`algorithm`

This may be a string or an object with a single property `name` that is a string. The string names 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`

An `ArrayBuffer`, a `TypedArray` or a `DataView` object containing the data to be digested.

### Return value

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.


| Algorithm | Output length (bits) | Block size (bits) | Specification |
| --- | --- | --- | --- |
| SHA-1 | 160 | 512 | FIPS 180-4, section 6.1 |
| SHA-256 | 256 | 512 | FIPS 180-4, section 6.2 |
| SHA-384 | 384 | 1024 | FIPS 180-4, section 6.5 |
| SHA-512 | 512 | 1024 | FIPS 180-4, section 6.4 |

**Warning:** SHA-1 is now considered vulnerable and should not
 be used for cryptographic applications.



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


Examples
--------

For more examples of using the `digest()` API, see Non-cryptographic uses of SubtleCrypto.

### Basic example

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


```js
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;
}

digestMessage(text).then((digestBuffer) =>
  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:


```js
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;
}

digestMessage(text).then((digestHex) => console.log(digestHex));
```

Specifications
--------------

| Specification |
| --- |
| Web Cryptography API # SubtleCrypto-method-digest |

Browser compatibility
---------------------

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

See also
--------

* Non-cryptographic uses of SubtleCrypto
* Chromium secure origins specification
* FIPS 180-4 specifies the SHA family of digest algorithms.