Atomics.isLockFree()
Baseline
Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since December 2021.
The Atomics.isLockFree() static method is used to determine whether the Atomics methods use locks or atomic hardware operations when applied to typed arrays with the given element byte size. It is intended as an optimization primitive, so that high-performance algorithms can determine whether to use locks or atomic operations in critical sections. If an atomic primitive is not lock-free, it is often more efficient for an algorithm to provide its own locking.
Try it
console.log(Atomics.isLockFree(3));
// 3 is not one of the BYTES_PER_ELEMENT values
// Expected output: false
console.log(Atomics.isLockFree(4));
// 4 is one of the BYTES_PER_ELEMENT values
// Expected output: true
Syntax
js
Atomics.isLockFree(size)
Parameters
size-
The size in bytes to check.
Return value
A true or false value indicating whether the operation is lock free.
- Always
trueifsizeis 4, because all known platforms support 4-byte atomic operations. - Always
falseif the given size is not one of theBYTES_PER_ELEMENTproperty of integer TypedArray types.
Examples
Using isLockFree
js
Atomics.isLockFree(1); // true (platform-dependent)
Atomics.isLockFree(2); // true (platform-dependent)
Atomics.isLockFree(3); // false
Atomics.isLockFree(4); // true
Atomics.isLockFree(5); // false
Atomics.isLockFree(6); // false
Atomics.isLockFree(7); // false
Atomics.isLockFree(8); // true (platform-dependent)
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-atomics.islockfree |
Browser compatibility
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