rel="preload" css tags with mod_pagespeed

[al...@cadence-labs.com]

Newer versions of mod_pagespeed will strip <link rel="preload" hints from the page and turn them into preload headers ... you can disable this feature, however doing so also disables pagespeed's ability to optimize the CSS.

If you are following this design pattern: https://github.com/filamentgroup/loadCSS of using rel="preload" to load non-critical css, this functionality results in the css getting stripped from the page content.

Is this intended behavior? 

[Joshua Marantz]

Sorry I need to re-read the preload spec.  But isn't 'preload" a hint that requires that a non-preload link tag also exist?  If that's right, then MPS should not be changing behavior by stripping the preloads, though it may harm performance.

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[al...@cadence-labs.com]

The preload tag should be independent of non-preload tags. 

I think mod pagespeed is trying to take a <preload link tag and turn it into a preload header. This would be fine, but if you review my original post one way that google encourages async loading of non-critical CSS is to use <link preloads with javascript that turn them into normal <link tags upon completion

[Adam Lane]

I am trying to use mod_pagespeed with loadCSS and having a problem I am unsure how to deal with:

   https://github.com/filamentgroup/loadCSS/issues/225

The heart of the matter seems to be that I have preload link tags with onload attributes and mod_pagespeed is removing them so the onload never fires.  I just stumbled into this issue so I am totally guessing but I suspect the solution is that hint_preload_subresources should not remove a preload link tag if it has an onload attribute?

[Otto van der Schaaf]

Filed https://github.com/pagespeed/mod_pagespeed/issues/1621 for tracking this

Otto