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PageSpeed support

Overview

PageSpeed (mod_pagespeed) optimizes your site and makes content load more quickly. PageSpeed applies a variety of filters including minifying scripts, inlining CSS, and automatically deferring JavaScript to avoid blocking DOM rendering. Users can browse your site with less latency, and in turn, improve visitor engagement.

Availability

PageSpeed is available on all v5+ platforms. PageSpeed is enabled by default.

Filter usage

PageSpeed is built as modular filters. These filters, in turn, may be added and removed to a web site resulting in a variety of optimizations. Filters may be added or removed in a .htaccess file.  By default, all filters listed in  CoreFilters (refer to Filter list) are enabled.

  1. Create a file named .htaccess in your document root if it does not already exist
    • To add filters: 
      ModPagespeedEnableFilters filtera,filterb
    • To remove filters:
      ModPagespeedDisableFilters filtera,filterb
  2. Once committed, these filters specified will be added or removed from CoreFilters

Filter list

Note: In the heading, “CF” is CoreFilters and OFB is “OptimizeForBandwidth”.

Filter Name In CF In OFB Brief Description
add_head Yes No Adds a <head> element to the document if not already present.
combine_heads No No Combines multiple <head> elements found in document into one.
inline_import_to_link Yes No Inlines <style> tags comprising only CSS @imports by converting them to equivalent <link> tags.
outline_css No No Externalize large blocks of CSS into a cacheable file.
outline_javascript No No Externalize large blocks of JS into a cacheable file.
move_css_above_scripts No No Moves CSS elements above <script> tags.
move_css_to_head No No Moves CSS elements into the <head>.
combine_css Yes No Combines multiple CSS elements into one.
rewrite_css Yes Yes Rewrites CSS files to remove excess whitespace and comments, and, if enabled, rewrite or cache-extend images referenced in CSS files. In OptimizeForBandwidth mode, the minification occurs in-place without changing URLs.
fallback_rewrite_css_urls Yes No Rewrites resources referenced in any CSS file that cannot otherwise be parsed and minified.
rewrite_style_attributes No No Rewrite the CSS in style attributes by applying the configured rewrite_css filter to it.
rewrite_style_attributes_with_url Yes No Rewrite the CSS in style attributes if it contains the text ‘url(‘ by applying the configured rewrite_css filter to it
flatten_css_imports Yes No Inline CSS by flattening all @import rules.
prioritize_critical_css No No Replace CSS tags with inline versions that include only the CSS used by the page.
make_google_analytics_async No No Convert synchronous use of Google Analytics API to asynchronous
rewrite_javascript Yes Yes Rewrites JavaScript files to remove excess whitespace and comments. In OptimizeForBandwidth mode, the minification occurs in-place without changing URLs.
rewrite_javascript_external Yes Yes Implied by rewrite_javascript. Rewrites JavaScript external files to remove excess whitespace and comments. In OptimizeForBandwidth mode, the minification occurs in-place without changing URLs.
rewrite_javascript_inline Yes Yes Implied by rewrite_javascript. Rewrites inline JavaScript blocks to remove excess whitespace and comments.
include_js_source_maps No No Adds source maps to rewritten JavaScript files.
combine_javascript Yes No Combines multiple script elements into one.
canonicalize_javascript_libraries No No Redirects JavaScript libraries to a JavaScript hosting service.
inline_css Yes No Inlines small CSS files into the HTML document.
inline_google_font_css No No Inlines small CSS files used by fonts.googleapis.com into the HTML document.
inline_javascript Yes No Inlines small JS files into the HTML document.
local_storage_cache No No Cache inlined resources in HTML5 local storage.
insert_ga No No Adds the Google Analytics snippet to each HTML page.
rewrite_images Yes Yes Optimizes images, re-encoding them, removing excess pixels, and inlining small images. In OptimizeForBandwidth mode, the minification occurs in-place without changing URLs.
convert_jpeg_to_progressive Yes Yes Converts larger jpegs to progressive format. Implied by recompress images.
convert_png_to_jpeg Yes Yes Converts gif and png images into jpegs if they appear to be less sensitive to compression artifacts and lack alpha transparency. Implied by recompress images.
convert_jpeg_to_webp Yes Yes Producess lossy webp rather than jpeg images for browsers that support webp. Implied by recompress images.
convert_to_webp_lossless No No Replaces gif and png images with webp images on browsers that support the format.
insert_image_dimensions No No Adds width and height attributes to <img> tags that lack them.
inline_images Yes No Implied by rewrite_images. Replaces small images bydata: urls.
recompress_images Yes Yes Implied by rewrite_images. Recompresses images, removing excess metadata and transforming gifs into pngs.
recompress_jpeg Yes Yes Implied by recompress_images. Recompresses jpegs, removing excess metadata.
recompress_png Yes Yes Implied by recompress_images. Recompresses pngs, removing excess metadata.
recompress_webp Yes Yes Implied by recompress_images. Recompresses webps, removing excess metadata.
convert_gif_to_png Yes Yes Implied by recompress_images. Optimizes gifs to pngs.
strip_image_color_profile Yes Yes Implied by recompress_images. Strips color profile info from images.
strip_image_meta_data Yes Yes Implied by recompress_images. Strips EXIF meta data from images.
jpeg_sampling Yes Yes Implied by recompress_images. Reduces the color sampling of jpeg images to 4:2:0.
resize_images Yes No Implied by rewrite_images. Resizes images when the corresponding <img> tag specifies a smaller widthand height.
resize_rendered_image_dimensions Yes No Implied by rewrite_images. Resizes an image when the rendered dimensions of the image are smaller than the actual image.
inline_preview_images No No Uses inlined low-quality images as placeholders which will be replaced with original images once the web page is loaded.
resize_mobile_images No No Works just like inline_preview_images, but uses smaller placeholder images and only serves them to mobile browsers.
remove_comments No No Removes comments in HTML files (but not in inline JavaScript or CSS).
collapse_whitespace No No Removes excess whitespace in HTML files (avoiding<pre>, <script>, <style>, and <textarea>).
elide_attributes No No Removes attributes which are not significant according to the HTML spec.
extend_cache Yes No Extends cache lifetime of CSS, JS, and image resources that have not otherwise been optimized, by signing URLs with a content hash.
extend_cache_css Yes No Implied by extend_cache. Extends cache lifetime of otherwise unoptimized CSS resources by signing URLs with a content hash.
extend_cache_images Yes No Implied by extend_cache. Extends cache lifetime of otherwise unoptimized images by signing URLs with a content hash.
extend_cache_scripts Yes No Implied by extend_cache. Extends cache lifetime of otherwise unoptimized scripts by signing URLs with a content hash.
extend_cache_pdfs No No Extends cache lifetime of PDFs by signing URLs with a content hash.
sprite_images No No Combine background images in CSS files into one sprite.
rewrite_domains No No Rewrites the domains of resources not otherwise touched by PageSpeed, based on MapRewriteDomainand ShardDomain settings in the config file.
trim_urls No No Shortens URLs by making them relative to the base URL.
pedantic No No Add default types for <script> and <style> tags if the type attribute is not present and the page is not HTML5. The purpose of this filter is to help ensure that PageSpeed does not break HTML4 validation.
remove_quotes No No Removes quotes around HTML attributes that are not lexically required.
add_instrumentation No No Adds JavaScript to page to measure latency and send back to the server.
convert_meta_tags Yes No Adds a response header for each meta tag with anhttp-equiv attribute.
defer_javascript No No Defers the execution of JavaScript in HTML until page load complete.
dedup_inlined_images No No Replaces repeated inlined images with JavaScript that loads the image from the first occurence of the image.
lazyload_images No No Loads images when they become visible in the client viewport.
insert_dns_prefetch No No Inserts <link rel="dns-prefetch" href="//www.example.com"> tags to reduce DNS resolution time.
in_place_optimize_for_browser No Yes Perform browser-dependent in-place resource optimizations.

 

See also

Updated on March 7, 2021

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