knorv knorv - 3 months ago 11x
HTML Question

Which browsers support <script async="async" />?

On December 1, 2009, Google announced support for asynchronous Google Analytics tracking.

The asynchronous tracking is achieved using the async directive for the


Which browsers support the async directive (
<script async="async" />
) and since which version?


The async support as specified by google is achieved using two parts:

  • using script on your page (the script is supplied by google) to write out a <script> tag to the DOM.

  • that script has async="true" attribute to signal to compatible browsers that it can continue rendering the page.

The first part works on browsers without support for <script async.. tags, allowing them to load async with a "hack" (although a pretty solid one), and also allows rendering the page without waiting for ga.js to be retrieved.

The second part only affects compatible browsers that understand the async html attribute

  • FF 3.6+
  • FF for Android All Versions
  • IE 10+ (starting with preview 2)
  • Chrome 8+
  • Chrome For Android All versions
  • Safari 5.0+
  • iOS Safari 5.0+
  • Android Browser 3.0+ (honeycomb on up)
  • Opera 15.0+
  • Opera Mobile 16.0+
  • Opera Mini None (as of 8.0)

The "html5 proper" way to specify async is with a <script async src="...", not <script async="true". However, initially browsers did not support this syntax, nor did they support setting the script property on referenced elements. If you want this, the list changes:

  • FF 4+
  • IE 10+ (preview 2 and up)
  • Chrome 12+
  • Chrome For Android 32+
  • Safari 5.1+
  • No android versions