Can I use
?

defer attribute for external scripts

- LS

The boolean defer attribute on script elements allows the external JavaScript file to run when the DOM is loaded, without delaying page load first.

Chrome

  1. ❌ 4 - 7: Not supported
  2. ✅ 8 - 132: Supported
  3. ✅ 133: Supported
  4. ✅ 134 - 136: Supported

Edge

  1. ✅ 12 - 131: Supported
  2. ✅ 132: Supported

Safari

  1. ❌ 3.1 - 4: Not supported
  2. ✅ 5 - 18.2: Supported
  3. ✅ 18.3: Supported
  4. ✅ 18.4 - TP: Supported

Firefox

  1. ❌ 2 - 3: Not supported
  2. ✅ 3.5 - 30: Supported
  3. ✅ 31 - 134: Supported
  4. ✅ 135: Supported
  5. ✅ 136 - 138: Supported

Opera

  1. ❌ 9 - 12.1: Not supported
  2. ✅ 15 - 113: Supported
  3. ✅ 114: Supported

IE

  1. ◐ 5.5 - 9: Partial support
  2. ✅ 10: Supported
  3. ✅ 11: Supported

Chrome for Android

  1. ✅ 132: Supported

Safari on iOS

  1. ❌ 3.2 - 4.3: Not supported
  2. ✅ 5 - 18.2: Supported
  3. ✅ 18.3: Supported
  4. ✅ 18.4: Supported

Samsung Internet

  1. ✅ 4 - 26: Supported
  2. ✅ 27: Supported

Opera Mini

  1. ❌ all: Not supported

Opera Mobile

  1. ❌ 10 - 12.1: Not supported
  2. ✅ 80: Supported

UC Browser for Android

  1. ✅ 15.5: Supported

Android Browser

  1. ❌ 2.1 - 2.3: Not supported
  2. ✅ 3 - 4.4.4: Supported
  3. ✅ 132: Supported

Firefox for Android

  1. ✅ 132: Supported

QQ Browser

  1. ✅ 14.9: Supported

Baidu Browser

  1. ✅ 13.52: Supported

KaiOS Browser

  1. ✅ 2.5: Supported
  2. ✅ 3: Supported
Resources:
MDN Web Docs - Script Attributes
has.js test
WebPlatform Docs
async vs defer attributes