Preload

Use of preload

Speed performance

Use of preload

SeoChecker indicates in a table like the one below preload candidates based on the third level of requests in the critical request chain.

How preload candidates are chosen by SeoChecker

Imagine this is a critical request chain of a page:

index.html
|--app.js
   |--styles.css
   |--ui.js

SeoChecker would choose ui.js and styles.css as candidates.

Indeed, <script src=”app.js”> is declared by the index.html file: once app.js runs, fetch() is called to download ui.js and styles.css.

As long as they are downloaded, parsed and executed, the page does not show up.

If you declare preload links, you can make the pages load faster: the potential savings depend on when the browser is able to initiate the requests.