Web/JavaScript/Reference/Global objects/Atomics

The Atomics object provides atomic operations as static methods. They are used with SharedArrayBuffer and ArrayBuffer objects.

Description

The Atomic operations are installed on an Atomics module. Unlike the other global objects, Atomics is not a constructor. You cannot use it with a new operator or invoke the Atomics object as a function. All properties and methods of Atomics are static (as is the case with the Math object, for example).

Atomic operations

When memory is shared, multiple threads can read and write the same data in memory. Atomic operations make sure that predictable values are written and read, that operations are finished before the next operation starts and that operations are not interrupted.

Wait and notify

The wait() and notify() methods are modeled on Linux futexes ("fast user-space mutex") and provide ways for waiting until a certain condition becomes true and are typically used as blocking constructs.

Static methods

Atomics.add(): Adds the provided value to the existing value at the specified index of the array. Returns the old value at that index.
Atomics.and(): Computes a bitwise AND on the value at the specified index of the array with the provided value. Returns the old value at that index.
Atomics.compareExchange(): Stores a value at the specified index of the array, if it equals a value. Returns the old value.
Atomics.exchange(): Stores a value at the specified index of the array. Returns the old value.
Atomics.isLockFree(size): An optimization primitive that can be used to determine whether to use locks or atomic operations. Returns true if an atomic operation on arrays of the given element size will be implemented using a hardware atomic operation (as opposed to a lock). Experts only.
Atomics.load(): Returns the value at the specified index of the array.
Atomics.notify(): Notifies agents that are waiting on the specified index of the array. Returns the number of agents that were notified.
Atomics.or(): Computes a bitwise OR on the value at the specified index of the array with the provided value. Returns the old value at that index.
Atomics.store(): Stores a value at the specified index of the array. Returns the value.
Atomics.sub(): Subtracts a value at the specified index of the array. Returns the old value at that index.
Atomics.wait(): Verifies that the specified index of the array still contains a value and sleeps awaiting or times out. Returns either "ok", "not-equal", or "timed-out". If waiting is not allowed in the calling agent then it throws an Error exception. (Most browsers will not allow wait() on the browser's main thread.)
Atomics.xor(): Computes a bitwise XOR on the value at the specified index of the array with the provided value. Returns the old value at that index.

Examples

Using Atomics

const sab = new SharedArrayBuffer(1024);
const ta = new Uint8Array(sab);

ta[0]; // 0
ta[0] = 5; // 5

Atomics.add(ta, 0, 12); // 5
Atomics.load(ta, 0); // 17

Atomics.and(ta, 0, 1); // 17
Atomics.load(ta, 0); // 1

Atomics.compareExchange(ta, 0, 5, 12); // 1
Atomics.load(ta, 0); // 1

Atomics.exchange(ta, 0, 12); // 1
Atomics.load(ta, 0); // 12

Atomics.isLockFree(1); // true
Atomics.isLockFree(2); // true
Atomics.isLockFree(3); // false
Atomics.isLockFree(4); // true

Atomics.or(ta, 0, 1); // 12
Atomics.load(ta, 0);  // 13

Atomics.store(ta, 0, 12); // 12

Atomics.sub(ta, 0, 2); // 12
Atomics.load(ta, 0); // 10

Atomics.xor(ta, 0, 1); // 10
Atomics.load(ta, 0); // 11

Waiting and notifiying

Given a shared Int32Array:

const sab = new SharedArrayBuffer(1024);
const int32 = new Int32Array(sab);

A reading thread is sleeping and waiting on location 0 which is expected to be 0. As long as that is true, it will not go on. However, once the writing thread has stored a new value, it will be notified by the writing thread and return the new value (123).

Atomics.wait(int32, 0, 0);
console.log(int32[0]); // 123

A writing thread stores a new value and notifies the waiting thread once it has written:

console.log(int32[0]); // 0;
Atomics.store(int32, 0, 123); 
Atomics.notify(int32, 0, 1);

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'Atomics' in that specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
`Atomics`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
Atomic operations on non-shared `ArrayBuffer` objects	Chrome No support No	Edge No support No	Firefox Full support 79	IE No support No	Opera No support No	Safari No support No	WebView Android No support No	Chrome Android No support No	Firefox Android Full support 79	Opera Android No support No	Safari iOS No support No	Samsung Internet Android No support No	nodejs No support No
`add`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`and`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`compareExchange`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`exchange`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`isLockFree`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`load`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`notify`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Alternate Name' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place. Alternate Name' Uses the non-standard name: `wake`	Edge Full support 79	Firefox Full support 78 Full support 78 Full support 63 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 63: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. Full support 57 Notes' Alternate Name' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Alternate Name' Uses the non-standard name: `wake` Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 48 — 55 Disabled' Disabled' From version 48 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 46 — 48 Notes' Alternate Name' Disabled' Notes' The `count` parameter defaults to `0` instead of the later-specified `+Infinity`. Alternate Name' Uses the non-standard name: `futexWake` Disabled' From version 46 until version 48 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1 Alternate Name' No support 10.1 — 11.1 Alternate Name' Alternate Name' Uses the non-standard name: `wake`	WebView Android No support 60 — 63 Notes' Alternate Name' No support 60 — 63 Notes' Alternate Name' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. Alternate Name' Uses the non-standard name: `wake`	Chrome Android No support 60 — 63 Notes' Alternate Name' No support 60 — 63 Notes' Alternate Name' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. Alternate Name' Uses the non-standard name: `wake`	Firefox Android Full support 63 Notes' Disabled' Full support 63 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 63: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. Full support 57 Notes' Alternate Name' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Alternate Name' Uses the non-standard name: `wake` Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 48 — 55 Disabled' Disabled' From version 48 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 46 — 48 Notes' Alternate Name' Disabled' Notes' The `count` parameter defaults to `0` instead of the later-specified `+Infinity`. Alternate Name' Uses the non-standard name: `futexWake` Disabled' From version 46 until version 48 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' Alternate Name' No support No Notes' Alternate Name' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. Alternate Name' Uses the non-standard name: `wake`	nodejs Full support 8.10.0 Alternate Name' Full support 8.10.0 Alternate Name' Alternate Name' Uses the non-standard name: `wake`
`or`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`store`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`sub`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`wait`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 48 — 55 Disabled' Disabled' From version 48 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 46 — 48 Notes' Alternate Name' Disabled' Notes' The method returns values `Atomics.OK`, `Atomics.TIMEDOUT`, and `Atomics.NOTEQUAL`, instead of the later-specified strings. Alternate Name' Uses the non-standard name: `futexWait` Disabled' From version 46 until version 48 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 48 — 55 Disabled' Disabled' From version 48 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 46 — 48 Notes' Alternate Name' Disabled' Notes' The method returns values `Atomics.OK`, `Atomics.TIMEDOUT`, and `Atomics.NOTEQUAL`, instead of the later-specified strings. Alternate Name' Uses the non-standard name: `futexWait` Disabled' From version 46 until version 48 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0
`xor`	Chrome Full support 68 Full support 68 No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place.	Edge Full support 79 Full support 79 No support 16 — 17 Notes' Notes' Support was removed to mitigate speculative execution side-channel attacks (Windows blog).	Firefox Full support 78 Full support 78 Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	IE No support No	Opera No support No	Safari No support 10.1 — 11.1	WebView Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Chrome Android No support 60 — 63 Notes' No support 60 — 63 Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	Firefox Android Full support 57 Notes' Disabled' Full support 57 Notes' Disabled' Notes' Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled' From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled' Disabled' From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config.	Opera Android No support No	Safari iOS No support 10.3 — 11.3	Samsung Internet Android No support No Notes' No support No Notes' Notes' Chrome disabled `SharedArrayBuffer` on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place.	nodejs Full support 8.10.0

Legend

Full support: Full support
No support: No support
See implementation notes.': See implementation notes.
User must explicitly enable this feature.': User must explicitly enable this feature.
Uses a non-standard name.': Uses a non-standard name.