Frequently Asked Questions

I updated my javascript/css/images, why do I still get the old version?

Css, javascript, images and other assets will be fetched over http by default, and will cached by ATSPageSpeed for the specified expiry time specified in the response headers.
ATSPageSpeed will check back at the expiry time by default (which can be shortened or lengthened through configuration), which is when ATSPageSpeed will notice any changes.
One way to work around this, is by configuring LoadFromFile.
Using LoadFromFile allows ATSPageSpeed to detect and reprocess files immediately after they are updated, and has other benefits as well.

Wy do I get a partially optimized response on the first request?

This is by design - ATSPageSpeed works under a tight deadline when rewriting html, and will send a partially optimized or unoptimized response when it would take too long to wait for optimizations to complete. By default ATSPageSpeed will wait for 50 ms. After a few refreshes, optimizations should be cached and ready, and you will get a fully optimized response. The deadline can be changed using RewriteDeadlinePerFlushMs value_in_milliseconds, where a value equal to or smaller then 0 will cause ATSPageSpeed to wait indefinitely until completion.
Also, ATSPageSpeed will usually only optimize cacheable assets (css/js/images), so make sure your expiration headers are set.

Why are rewritten pages sending POSTs back to my server?

Certain filters need to determine things about the page: in particular, the lazyload_images, inline_preview_images, and inline_images filters need to determine which images are above the fold, and the prioritize_critical_css filter needs to determine the CSS actually used by the page.

To do this, the filters inject JavaScript into the rewritten HTML that analyzes the page in the browser and sends data back to mod_pagespeed using a POST method. The default target is /pagespeed_beacon but that can be changed using the BeaconUrl directive.

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