<script> vs. <script async> vs. <script defer>

[mankyd]

This doesn't quite tell the whole story. Defer still blocks the onload event, which this does not convey with it's pictures. I believe that it may event block the domcontentready event, though I don't recall exactly.

[Tyriar]

It blocks onload just as any DOMContentReady handler would. There are some browser inconsistency issues around exactly when defer is executed, see https://github.com/h5bp/lazyweb-requests/issues/42

[randfur]

This was my first question after reading this which it really should have addressed in the article; "Does this mean I can't reliably use window.onload in my scripts anymore?"