Error.isError()Limited availability
The Error.isError() static method checks whether a value is an Error object.
Not yet supported in all major browsers — check the table and provide a fallback.
Browser support
DesktopChrome
1–133Not supported
134+Supportedsince Mar 4, 2025
Current: 155Edge
12–133Not supported
134+Supportedsince Mar 6, 2025
Current: 154Firefox
1–137Not supported
138+Supportedsince Apr 29, 2025
Current: 157Safari
✕Not supportedup to 27
Current: 27MobileChrome Android
18–133Not supported
134+Supportedsince Mar 4, 2025
Current: 155Firefox Android
4–137Not supported
138+Supportedsince Apr 29, 2025
Current: 157Safari iOS
✕Not supportedup to 27
Current: 27How to use
Not supported in Safari, Safari iOS. Use feature detection below and provide a fallback (or a polyfill) for those browsers.
Example
Full syntax and examples are on MDN: isError.
Feature detection
JS · check before using
if ("isError" in Error || ("prototype" in Error && "isError" in Error.prototype)) {
// Error.isError is available
}