import deferLimited availability
The import defer and import.defer() JavaScript statements import a module while deferring its evaluation until its first use.
Not yet supported in all major browsers — check the table and provide a fallback.
Browser support
DesktopChrome
✕Not supportedup to 155
Current: 155Edge
✕Not supportedup to 154
Current: 154Firefox
✕Not supportedup to 157
Current: 157Safari
✕Not supportedup to 27
Current: 27MobileChrome Android
✕Not supportedup to 155
Current: 155Firefox Android
✕Not supportedup to 157
Current: 157Safari iOS
✕Not supportedup to 27
Current: 27How to use
Not supported in Chrome, Edge, Firefox, Safari, Chrome Android, Firefox Android, Safari iOS. Use feature detection below and provide a fallback (or a polyfill) for those browsers.
Example
Full syntax and examples are on MDN: defer.
Feature detection
JS · check before using
// Syntax can't be tested with an if-statement — an unsupported
// browser fails to parse the whole script. Either transpile for older
// targets (e.g. Babel/TypeScript/esbuild), or probe in isolation:
let supported = true;
try {
new Function("/* code that uses the syntax */");
} catch {
supported = false;
}This is a language syntax feature.
Specification
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 |
|---|---|---|---|---|---|---|---|
| import.defer | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ |
| import.defer | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ |