Threads and atomics (WebAssembly)Baseline · Widely available
Threads in WebAssembly run code in parallel, while atomic memory instructions can guarantee that no two threads can read or write to shared memory at the same time.
Supported in all major browsers for at least 30 months — safe to use without fallbacks. Baseline since Dec 13, 2021. Widely available since Jun 13, 2024.
Browser support
DesktopChrome
1–73Not supported
74+Supportedsince Apr 23, 2019
Current: 155Edge
12–18Not supported
79+Supportedsince Jan 15, 2020
Current: 154Firefox
1–78Not supported
79+Supportedsince Jul 28, 2020
Current: 157Safari
1–15.1Not supported
15.2+Supportedsince Dec 13, 2021
Current: 27MobileChrome Android
18–87Not supported
88+Supportedsince Jan 19, 2021
Current: 155Firefox Android
4–68Not supported
79+Supportedsince Jul 28, 2020
Current: 157Safari iOS
1–15.1Not supported
15.2+Supportedsince Dec 13, 2021
Current: 27How to use
This feature is Baseline widely available — use it freely, no fallback needed.
Example
Full syntax and examples are on MDN — see the links below.
Feature detection
There’s no simple runtime check for this feature; rely on the support table and test in your target browsers.
Sub-features
Support for each part of the feature (2). The overall table above shows when the whole feature works.
| Sub-feature | Chrome | Edge | Firefox | Safari | Chrome Android | Firefox Android | Safari iOS |
|---|---|---|---|---|---|---|---|
| webassembly.api.Memory.Memory.shared | 74 | 79 | 78 | 15.2 | 88 | 79 | 15.2 |
| webassembly.threads-and-atomics | 74 | 79 | 79 | 15.2 | 88 | 79 | 15.2 |