Here are some of the most useful filters provided by mod_pagespeed. Each one has a simple HTML example attached; click "before" to see the original file, and "after" to see what mod_pagespeed produces with that filter (and only that filter) enabled. The two versions should look exactly the same, but the "after" one will be (slightly) speedier. Use "view source" to see the mod_pagespeed difference!
add_instrumentation | Adds client-side latency instrumentation. | before | after |
extend_cache | Improves cacheability. | before | after |
collapse_whitespace | Removes unnecessary whitespace in HTML. | before | after |
combine_css | Combines multiple CSS files into one. | before | after |
combine_javascript | Combines multiple JavaScript files into one. | before | after |
combine_heads | Combines multiple <head> elements into one. | before | after |
defer_javascript | Defers the execution of javascript in the HTML. | before | after |
move_css_above_scripts | Moves CSS Above Scripts. | before | after |
move_css_to_head | Moves CSS into the <head> element. | before | after |
elide_attributes | Removes unnecessary attributes in HTML tags. | before | after |
inline_css | Inlines small external CSS files. | before | after |
inline_import_to_link | Inlines style tags comprising a single CSS @import by converting them to an equivalent link. | before | after |
flatten_css_imports | Flattens @import rules in CSS by replacing the rule with the contents of the imported resource. | before | after |
inline_javascript | Inlines small external Javascript files. | before | after |
lazyload_images | Loads images when they become visible in the client viewport. | before | after |
local_storage_cache | Loads inlined CSS and image resources into HTML5 local storage whence the client fetches them subsequently rather than the server sending them again. | before | after |
outline_css | Moves large inline <style> tags into external files for cacheability. | before | after |
outline_javascript | Moves large inline <script> tags into external files for cacheability. | before | after |
remove_quotes | Removes unnecessary quotes in HTML tags. | before | after |
remove_comments | Removes HTML comments. | before | after |
rewrite_style_attributes | Rewrite the CSS in style attributes by applying the configured rewrite_css filter to it. | before | after |
rewrite_style_attributes_with_url | Rewrite the CSS in style attributes by applying the configured rewrite_css filter to it, but only if the attribute contains the text 'url('. | before | after |
trim_urls | Removes unnecessary prefixes from URLs. | before | after |
make_google_analytics_async | Converts synchronous Google Analytics code to load asynchronously. | before | after |
rewrite_css | Minifies CSS. | before | after |
rewrite_css + cache_extend | Cache extends images in CSS. | before | after |
rewrite_css + rewrite_images | Re-compress images in CSS. | before | after |
rewrite_images | Rescales, and compresses images; inlines small ones. | before | after |
rewrite_javascript | Minifies Javascript. | before | after |
sprite_images | Sprites images. | before | after |
insert_ga | Inserts Google Analytics javascript snippet. | before | after |
inline_preview_images | Delays original images; serves inlined, low-quality placeholder images until originals are loaded. | before | after |
resize_mobile_images | Just like inline_preview_images, but uses smaller placeholder images for mobile browsers. | before | after |