A very fast caching engine for WordPress that produces static html files.
Enable debugging in the plugin settings page and load the log file in a new browser tab. Then view your blog while logged in and logged out. You should see activity in the log. View the source of any page on your site. When a page is first created, you'll see the text "Dynamic page generated in XXXX seconds." and "Cached page generated by WP-Super-Cache on YYYY-MM-DD HH:MM:SS" at the end of the source code. On reload, a cached page will show the same timestamp so wait a few seconds before checking. In legacy caching mode, if you have compression enabled, the text "Compression = gzip" will be added. If compression is disabled and the page is served as a static html file, the text "super cache" will be added. The only other way to check if your cached file was served by PHP script or from the static cache is by looking at the HTTP headers. PHP cached pages will have the header "WP-Super-Cache: Served supercache file from PHP". Legacy cached files will have the header, "WP-Super-Cache: Served legacy cache file". I used the Live HTTP Headers extension for Firefox to examine the headers. You should also check your cache directory in wp-content/cache/supercache/hostname/ for static cache files. If the plugin rules are missing from your .htaccess file, the plugin will attempt to serve the super cached page if it's found. The header "WP-Super-Cache: Served supercache file from PHP" if this happens.
WP-Cache files are stored in wp-content/cache/ (or on MU sites in a blogs sub directory) and are named wp-cache-XXXXXXXXXXXXXXXXX.html. Associated meta files are stored in a meta sub directory. Those files contain information about the cached file. These files are generated by the "legacy caching" code in the plugin. Supercache files are stored in wp-content/cache/supercache/HOSTNAME/ where HOSTNAME is your domain name. The files are stored in directories matching your site's permalink structure.
This plugin is based on the excellent WP-Cache plugin. Besides the caching WP-Cache did this plugin creates copies of every page that is accessed on a blog in a form that is quickly served by the web server. It's almost as quick as if the you had saved a html page in your browser and uploaded it to replace your homepage.
No, it will do the opposite. Super Cache files are compressed and stored that way so the heavy compression is done only once. These files are generally much smaller and are sent to a visitor's browser much more quickly than uncompressed html. As a result, your server spends less time talking over the network which saves CPU time and bandwidth, and can also serve the next request much more quickly.
Note: this functionality is disabled by default. You will have to enable it on the Advanced Settings page.
WP Super Cache 1.4 introduced a cacheaction filter called wpsc_cachedata. The cached page to be displayed goes through this filter and allows modification of the page. If the page contains a placeholder tag the filter can be used to replace that tag with your dynamically generated html. The function that hooks on to the wpsc_cachedata filter should be put in a file in the WP Super Cache plugins folder unless you use the late_init feature. An example plugin is included. Edit dynamic-cache-test.php to see the example code. There are two example functions there. There's a simple function that replaces a string (or tag) you define when the cached page is served. The other example function uses an output buffer to generate the dynamic content. Due to a limitation in how PHP works the output buffer code MUST run before the wpsc_cachedata filter is hit, at least for when a page is cached. It doesn't matter when serving cached pages. See this post for a more technical and longer explanation. To execute WordPress functions you must enable the 'Late init' feature on the advanced settings page.
Cached files are served before almost all of WordPress is loaded. While that's great for performance it's a pain when you want to extend the plugin using a core part of WordPress. Enable 'Late init' mode on the Advanced settings page and cached files will be served when "init" fires. WordPress and it's plugins will be loaded now.
WordPress deletes the plugin folder when it updates a plugin. This is the same with WP Super Cache so any modified files in wp-super-cache/plugins/ will be deleted. You can define the variable $wp_cache_plugins_dir in wp-config.php or wp-content/wp-cache-config.php and point it at a directory outside of the wp-super-cache folder. The plugin will look there for it's plugins.
When a visitor leaves a comment the cached file for that page is deleted and the next visitor recreates the cached page. A page takes time to load so what happens if it receives 100 visitors during this time? There won't be a cached page so WordPress will serve a fresh page for each user and the plugin will try to create a cached page for each of those 100 visitors causing a huge load on your server. This feature stops this happening. The cached page is not cleared when a comment is left. It is marked for rebuilding instead. The next visitor will regenerate the cached page while the old page is served to the other 99 visitors. The page is eventually loaded by the first visitor and the cached page updated. See this post for more.
Those bots usually only visit each page once and if the page is not popular there's no point creating a cache file that will sit idle on your server. However if you're not using legacy caching you can allow these visits to be cached by removing the list of bots from "Rejected User Agents" on the Advanced settings page.
A tiny proportion of websites will have problems with the following configuration:
Sometimes a category page is cached as the homepage of the site instead of the static page. I can't replicate the problem but a simple solution is to switch the plugin to PHP mode. For normal traffic you will see no difference in the speed of your site. You can also enable "Extra homepage checks" on the Advanced Settings page.
"Your blog doesn't support client caching (no 304 response to If-modified-since)." "Your feed doesn't support caching (no 304 response to If-modified-since)"
Supercache doesn't support 304 header checks in mod_rewrite mode but does support it in PHP mode. This is caching done by your browser, not the server. It is a check your browser does to ask the server if an updated version of the current page is available. If not, it doesn't download the old version again. The page is still cached by your server, just not by your visitors' browsers. Try the Cacheability Engine at http://www.ircache.net/cgi-bin/cacheability.py or http://redbot.org/ for further analysis.
That tracking adds a query string to each url linked from various sources like Twitter and feedreaders. Unfortunately it stops pages being supercached. See Joost's comment here for how to turn it into an anchor tag which can be supercached.
It's not good when the web server can write to these directories but sometimes shared hosting accounts are set up in this way to make administration easier. Use
chmod 755 directory to fix the permissions or find the permissions section of your ftp client. This Google search will lead you to more information on this topic and there's also this codex page too. Unfortunately some hosts require that those directories be writable. If that's the case just ignore this warning.
Load your desktop ftp client and connect to your site. Navigate to the root (or the directory below it) of your site where you'll find wp-config.php. Download that file and edit it in a text editor. Delete the line
define( 'WP_CACHE', true ); and save the file. Now upload it, overwriting the wp-config.php on your server.
Load your desktop ftp client and connect to your site. You may need to enable "Show hidden files" in the preferences of the ftp client. Navigate to the root of your site where you'll find the .htaccess file. Download that file and edit it in a text editor. Delete the lines between "# BEGIN WPSuperCache" and "# END WPSuperCache" and save the file. Now upload it, overwriting the .htaccess file on your server.
This page on the WordPress Codex explains everything you need to know about file permissions on your server and various ways of changing them.
You may have the "clear all cached files when new posts are made" option set. Clearing those files can take time plus your visitors will now be visiting uncached pages. Are you using Google Analytics campaign tracking with utm_source in the url? Those pages aren't cached. See the question, "How should I best use the utm_source tracking tools in Google Analytics with this plugin" above for how to use them properly. Cached pages have to be refreshed when posts are made. Perhaps your server just isn't up to the job of serving the amount of traffic you get. Enable the "cache rebuild" feature as that may help.
The only real limit are limits defined by your server. For example, EXT2 and EXT3 allow a maximum of 31,999 sub directories so if you have a flat permalink structure (like /%POSTNAME%/) and more than 32,000 posts you may run into problems. Likewise, if you run a multisite network and have more than 31,999 sites (blogs) you won't be able to cache all of them. Realistically if you had that many active sites you wouldn't be running on one server.
You'll have to use a separate mobile plugin to render a page formatted for those visitors. The following plugins have been tested but YMMV depending on mobile client.
If things don't work when you installed the plugin here are a few things to check:
Make sure the following line is in wp-config.php and it is ABOVE the "require_once(ABSPATH.'wp-settings.php');" line:
define( 'WP_CACHE', true );
Garbage collection of old cache files won't work if WordPress can't find wp-cron.php. If your hostname resolves to 127.0.0.1 it could be preventing the garbage collection from working. Check your access_logs for wp-cron.php entries. Do they return a 404 (file not found) or 200 code? If it's 404 or you don't see wp-cron.php anywhere WordPress may be looking for that script in the wrong place. You should speak to your server administator to correct this or edit /etc/hosts on Unix servers and remove the following line. Your hostname must resolve to the external IP address other servers on the network/Internet use. See http://yoast.com/wp-cron-issues/ for more. A line like "127.0.0.1 localhost localhost.localdomain" is ok.
If supercache cache files are generated but not served, check the permissions on all your wp-content/cache/supercache folders (and each of wp-content cache and supercache folders) and wp-content/cache/.htaccess. If your PHP runs as a different user to Apache and permissions are strict Apache may not be able to read the PHP generated cache files. To fix you must add the following line to your wp-config.php (Add it above the WP_CACHE define.) Then clear your cache.
umask( 0022 );
If you see garbage in your browser after enabling compression in the plugin, compression may already be enabled in your web server. In Apache you must disable mod_deflate, or in PHP zlib compression may be enabled. You can disable that in three ways. If you have root access, edit your php.ini and find the zlib.output_compression setting and make sure it's "Off" or add this line to your .htaccess:
php_flag zlib.output_compression off
If that doesn't work, add this line to your wp-config.php:
If certain characters do not appear correctly on your website your server may not be configured correctly. You need to tell visitors what character set is used. Go to Settings->Reading and copy the 'Encoding for pages and feeds' value. Edit the .htaccess file with all your Supercache and WordPress rewrite rules and add this at the top, replacing CHARSET with the copied value. (for example, 'UTF-8')
Requires: 3.0 or higher
Compatible up to: 4.2.2
Last Updated: 2015-5-15
Active Installs: 1+ million
27 of 180 support threads in the last two months have been resolved.
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