WP Super Cache

WP Super Cache has just been released! This version works with WordPress 3.0 and adds a number of new features and bug fixes:

  • Cache Preloading will cache every post on your site.
  • A cache tester that will check if your homepage is cached.
  • Much better support for mobile plugins.
  • Mod rewrite rules can now be updated from within the admin page.
  • Lots and lots of bugs fixed. See the changelog for more details.

Preloading creates lots of files on your server so if you have many thousands of posts please be aware of this. Filesystem limitations may cause problems if you use a flat permalink structure. For example, ext2 or ext3 only allows 32,000 directories in a directory. If you have more than that number of posts you may run into problems.

The plugin does not preload category or tag pages but because your single posts will be cached you’ll find the load on your server will be reduced. Uncached pages will be served more quickly and your visitors will have a quicker and better experience on your site.
You may also see an increase in site traffic if your server was previously underpowered!

Update! I just released to address the (mostly minor) bugs that were reported overnight. If you don’t notice anything wrong there’s no need to upgrade.

Author: Donncha

Donncha Ó Caoimh is a software developer at Automattic and WordPress plugin developer. He posts photos at In Photos and can also be found on Google+ and Twitter.

130 thoughts on “WP Super Cache”


    I’ll be testing this Cache Preloading thing with much pleasure! First question: If I set “Refresh preloaded cache files” to 0, does that still mean when a post receives a new comment, its cached file gets refreshed?

    Oh, and did I mention how GREAT this new version is? 😉

    1. No, it means that the plugin won’t automatically preload the cache again. You’ll have to manually preload it. I have mine set to 1440 so it refreshes once a day or so, but I’ll probably change that to 3 days or maybe 7 days. No need for the cached pages on my blog to be recycled.

      Leaving a comment or the same operations that used to refresh cached pages will still refresh those pages, regardless of what’s in that box.

      1. Thanks for that clarification.

        So if I set it to a few days, does that mean that new comments will not show (to search engines, the not-logged-in and non-commenters) until after the next preload? Or is teh cahced version of pages/posts that receive a comment immediately refreshed?

        1. No, like I said in my previous reply, “Leaving a comment … … will still refresh those pages”.

          They’ll be refreshed immediately. “Lockdown” mode stops pages refreshing. Not preloading.

  2. Super excited for cache preloading 😀 I’ve got a few pages that I open up after I manually clear the cache–while this method is a bit overkill to get those, it’s nice to just click a button and have everything optimized shortly thereafter. Great work!

  3. What happened to the “clear cache” button? How can I clear the cache now (note that I did turn on the preload cache)?

    Also, could someone please explain the preload mode checkbox better and say if it’s a good idea to turn it on and why?

      1. Yes, clicking “Regenerate stats” helped – the whole section came up, with the clear cache button too. You might investigate if the cache actually had taken place before I regenerated the stats.

      2. I did browse my blog a bit and the counters in the stats were all at 0. I hit the regenerate stats button again and it refreshed to the proper value.
        To sum up, the update has broken these counters and they are working only when manually regenerating stats. Hope it helps.

        1. Chris – The counters will only update when you hit “Regenerate cache stats”. Because of the new preloading, sites could have thousands of cached pages and it hinders administration if the admin page tries to scan the cache each time. I need to make that clearer.

    1. Yes, it is a good idea to turn it on. Your supercache files won’t be cleaned up and deleted when they get old, but wp-cache files will. (See readme.txt for distinction between the two)

  4. I know this may be a difficult question to answer, but do you think the preload cache is appropriate for a shared hosting environment? Will it completely bog down the server? Would have the preload happen in the middle of night during presumably low server load help? If I stayed up late one night and initiated the preload, say at 2:00am, would the preload then re-cache start its next preload a this time (assuming I set up a preload time in intervals of 24 hours). Thanks! Chris

    1. CFisher – it’s definitely appropriate. The preloading function loads posts one after another so it shouldn’t put excessive strain on your site. It doesn’t request loads of posts at the same time.

  5. Hello, thank you very much once again for the brilliant work, the preload new function looks brilliant !

    At the present time, the only thing I can do to help is debugging, and I found a partial incompatibility with the extremely popular wp-postratings plugin.

    Visitors may rate a post, this rating is memorized, however for non-admin-loggerd visitors this rating is NOT shown until the cache is cleared.

    The URL of this plugin, if needed : http://lesterchan.net/portfolio/programming/php/

    Maybe you can do something about it, maybe you won’t care, but at least I made my report 🙂

    Thanks a lot, once again, for all the great work !

    Best regards,

  6. On the “preload cache” mode, what’s consider “lots of posts?” I understand that it can be server intensive, but what’s the cutoff there? I’m over 550 now, but I know people who have ten times that, so maybe my amount isn’t a “lot” in that sense. Is it still alright for me to use the preload caching feature (and not make Bluehost angry)?

      1. Haha, I’ve got almost 10 times that many posts and I’ve got them all cached. This server hums along barely doing anything most of the time now.

  7. I’ve been testing the preload feature for several weeks on a blog with over 20,000 posts. The OS is RedHat ES 5, running WordPress 2.9.2, and memcached to cache database transactions.

    As the preload filled with posts the server load remained about the same, the memcached hits decreased by about 66%, and the RAM used increased significantly as the OS cached frequently used files in the preload cache.

    The RAM usage wasn’t exactly expected, but it can be detrimental on a server with a lot of posts, but not a lot of RAM. The server I tested this on has a lot of RAM so it wasn’t a problem.

    What made the biggest difference on server load for this blog was using memcached for database transactions, which is running on the same server. I also use APC on the same server to cache PHP scripts, which also helps decrease the server load.

    The RAM usage by the preload cache adding files and directories on the disk decreases the amount of RAM available for heavy traffic loads.

    I also noted that Google crawled less than half of my posts after less than a week of using a fully loaded preload cache. This negatively affected the amount of traffic to this blog.

    I tested this on a highly trafficked blog to get the best results.

    For this blog it is better not to use the preload, because it needs the RAM for heavy traffic spikes, Google sends less traffic, and Google crawls the site less perhaps because it believes the files are static so they haven’t changed.

    Thank you for leaving us the option not to use preload.

    1. Thanks for the info Todd. Good to see memcached hits go down, and it makes sense that RAM was used to cache files. Unused RAM on a server is wasted RAM. Memory is a useful resource so it makes sense to use as much of it as possible. I found this very useful post on why cached memory is good.

      20,000 posts is a hell of a lot of posts though so perhaps you should cache a smaller number of posts, maybe 5,000? The plugin preloads from the newest posts to older so you’ll get the newest 5,000 posts. At least then those posts won’t require CPU processing to run PHP scripts, make db calls, make memcached calls etc, when loaded.

      Google will in future/or is already using speed as a metric to determine how good a site is. It’s probably good to have some portion of your (huge) site preloaded.

      1. I will try preload caching a lower number of posts.

        Many of the posts Google uses to measure site speed are older posts getting traffic spikes, which will not be preloaded because they are older, unless I preload cache all the posts on the blog. I’ve noted the one factor that has the biggest impact on speed on this blog are ads on the pages. Even Google ads slow the post pages down considerably.

        Google should consider measuring page speed by factoring out the ads on the page and returning the page speed result without those ads. The biggest sites on the Internet generate the slowest speeds because they run ads to pay their bills, yet they are penalized the most by Google. However, since those same sites are very popular the traffic still comes in despite Google’s lower ranking, which is not realistic. For this reason I believe Google will eventually abandon the speed metric, except for information purposes.

  8. We manage about 200 websites (and growing) on an MU installation. We’re digging into performance optimization and installing WP Super Cache is at the top of our list.

    We’re stuck at WPMU 2.7.1 until we can fix a few bugs and upgrade.

    Does anybody know of any issues with WP Super Cache on MU 2.7 that we should look into?

    Also, does anybody provide support/consulting for WP Super Cache?


    1. The main thing is that preloading only works on the blog you’re on, not all blogs. If you want to preload all blogs you’ll have to visit each one.

      1. That’s fine. So if we manually update each existing one, and add that to our new site setup process, we’ll be okay?

        Is the cache cleared if a widget sidebar is updated?

        1. Yeah, you’ll have to manually do it.

          The cache isn’t cleared when the widget sidebar is updated AFAIR. I couldn’t find an action to hook on to fire off.

          1. Thanks Donncha. I’m sorry, what’s AFAIR?

            If the cache isn’t cleared each time a widget sidebar is updated, how can we make sure that pages are displaying up to date content?

          2. “As Far As I Recall”

            Normally widgets aren’t updated that often so it hasn’t been an issue so far. If you can find an action I can use I’ll add it to the next version.

            Meanwhile, if it’s a widget you’ve created yourself, you could use something like this if your widget fires an action when it’s updated by a human on the widgets page.

            add_action('switch_theme', 'wp_cache_no_postid', 99);

            Replace “switch_theme” with your own action.

            Widgets that update themselves, like RSS widgets won’t update until the cached page refreshes. This is a problem with all full page caching plugins. There’s a FAQ on it in the readme.txt

          3. Thank you so much for your help. Do you, or do you know anybody who provides consulting, implementation and support for this plugin?

          4. I do support on the plugin forum but I don’t have time to do consulting or anything else. A good WP or PHP developer will be able to find their way around the plugin though.

  9. i wonder why my trackback doesn`t come through. great to read the new features, i`m going to update from the early test versions through this final. thank you very much, donncha ! 🙂

  10. I have this error:

    Warning: Division by zero in /var/www/vhosts/meinetechwelt.net/httpdocs/wp-content/plugins/wp-super-cache/wp-cache.php on line 1745

    With the other Version i dont have this problem. How can i enable Preload Cahche?

    1. Martin – I’ve got that fixed in the development version. It only affects those who use the plugin in half-on mode but I’ll have to make a minor release this morning with that fix, plus the disappearing “Delete cache” button problem.

  11. Hi Donncha. Thanks for this latest development for a great plugin.

    I have a question about the cache preloading. My site uses the On This Day plugin to display links to other pages with the same date. The results change at midnight.

    With the minimum 720-minute (12-hour) refresh of the preload cache files, there’s a danger that the On This Day information would be out of date for up to 12 hours, which I’d obviously rather avoid.

    Is the 720 minute figure just a recommendation, and would it be a problem to lower this to, say, 180 minutes? I currently have around 2,500 pages on my site.

    1. It’s a recommendation because it takes so long to cache posts. If you preload too often you might as well not preload at all unfortunately.

      The best thing to do would be rewriting that plugin so it outputs a .js file that can be loaded by your blog. It’ll be update as soon as time changes.

      Or just don’t worry about it because the “On This Day” output will be right for those visitors who aren’t near your timezone. 🙂

    1. That’s odd. Did you press return, or click “Update Settings” or “Preload Cache Now” after changing it?

      It works for me when I change it and press return.

  12. Thanks for the update and your support here in the comments!
    Martin: maybe you have this plugin “half on” or even “off” at the top of its config page?

      1. Martin – you’ll have to open up wp-cache.php and look for the text “custom_preload_interval” and try to debug it when you submit that form. Or else you can edit wp-content/wp-cache-config.php and change “$wp_cache_preload_interval” to whatever interval you want.

          1. And what number do you see when I have XXX in this string? It’s right next to the refresh time.

            “(0 to disable, minimum XXX minutes.)”

          2. I see 60.

            if ( $_POST[ ‘custom_preload_interval’ ] != 0 )
            wp_schedule_single_event( time() + ( $_POST[ ‘custom_preload_interval’ ] * 60 )

          3. Oh my good, big sorry lol. I dont have read all. You write minimum 30 minutes (i have not see this). when i hit 10 this can not work. Big Sorry.

  13. I was wondering: Have you addressed any of the issues with object cache plugins? I was unable to make your product work with object cache and eAccelerator in previous versions? How’s this coming?


    1. No, I haven’t done any work on it. I simply don’t have time. It did work with memcached when I tried it. I briefly used xcache here (as an object cache, not with this plugin) a few weeks ago and it proved unreliable so I haven’t pursued it.

  14. Well, reason I use eAccelerator is that the installation is supported and available via cPanel. Anyway, I’ll give it a whirl. At worst it won’t work, and I’ll let you know. I realize you must have a day job. 🙂


      1. Use the cache tester, or check the timestamps match on consecutive reloads of a page. If you’re really paranoid, check wp-content/cache to make sure there’s nothing in there!

  15. Donncha,

    One suggestion. When the command “Delete Cache” is used the Admin page is reloaded. It would be good if activating “Delete Cache” would also trigger the “Regenerate cache stats” command.

  16. Wow..always something surprising come up with Wp-SuperCache. Glad I’m still sticking with it even though some asked me to move to.. (I forgot that its name is that’s supposed to be more “powerful” heh)

    Gonna try the pre-loading now

  17. Thanks for this update Donncha.
    I have two questions,
    What happens when a comment is posted after ticking the ‘Only refresh the current page when a comment is posted’ option?
    Does the cache rebuild take place only for that post and when?
    (Few of my best posts, almost receive a comment every minute, so if I understand it correctly, those posts will never be Gzipped?)
    Second, what happens when a new post is published after the cache re build? When does the cache build for this ‘new post’?

    1. Graham:
      1. Only the current page is refreshed, the homepage and other tag/category pages aren’t.
      2. Yes. It will be rebuilt when a visitor visits the page again.
      3. They will be gzipped if you have it enabled. No reason why not.
      4. See 2. The cache is built when someone views the post on your blog.

      1. Thanks for reply but I’m not seeing it come on my site.
        The cache was preloaded and there were some 1222 Super cache files. I visit a page on my site, see the source and found the GZip (which is enabled by the way). I leave a comment on that page and see the source again and find that there is no Gzip and the page is freshly cached.
        I reload the page (after clearing the cache of my browser) and still don’t see the Gzip comment in the source.
        This is not happening on your site (Ocaoimh). I leave a comment, for example this comment, on a Gzipped page and even after submitting the comment, I find the Gzip comment in the source.
        What is wrong with my settings?
        I’m on ON mode with SC with mobile support and ‘refresh the page only when a comments are made’ box ticked, compression enabled.

        1. Graham – try the debug system in the plugin. That will tell you what’s happening. It might shed some light on why it’s not serving gzipped cached pages for you.

          1. Is there any downside in leaving the ‘regenerate preload cache’ to ‘0’?
            Like Google thinking it to be an old post and dropping it? (Is there any way to find the post age from the cache?)
            Since I would (almost) never make changes to posts that are already published, except that comments keep coming, I would like to leave it at ‘zero’.

  18. Dear Donncha, i am running wordpress blog and every week i revcieved notification from shared hosting server.my blog has 1000 posts and i update after 15 days means twice a month. i just need recommended setting for my blog.
    Which options i’ve to check or uncheck?
    Refresh preloaded cache time?
    expiry time?
    Waiting for your kind response.

  19. Donncha,

    When WordPress 3.0 was released yesterday I ran into a problem. I used Memcached to cache database objects for WordPress, and I’ve used Xcache in the past, for several single install blogs that do not use WordPress MU. I used the drop-in plugin http://plugins.trac.wordpress.org/browser/memcached/.

    When I setup WordPress 3.0 I could not get it to work properly with the Memcached plugin linked above. The logins were no longer unique, and I could not find a solution. I thought perhaps WordPress would have documented a solution since they integrated WordPress MU into the 3.0 release, but I couldn’t find the information for single blog installs to keep the logins unique with a wp-config.php entry as I’ve used for years.

    In wp-config.php I entered the following two lines to make my single blog installation logins, and database object caching, unique in Memcached:

    global $blog_id;
    $blog_id = ‘www_domainname_com’;

    At the end of my efforts I had to stop using Super Cache and switch over to W3 Total Cache, only because W3TC had built-in support for Memcached, APC, Xcache, and eAccelerator for database and page caching.

    When using the drop-in plugin linked above I averaged 99% efficiency with Memcached, but the W3TC the efficiency is only 66%, which is why I would prefer not to use it at all.

    My preference is to use Super Cache, and the drop-in Memcached plugin linked above as I’ve been using for years, but I cannot find a solution to keep the logins unique. If you can write a solution into Super Cache, or send me some links to where I mind find a solution to my problem I would continue to use Super Cache.

    I am very grateful for all the time you put into Super Cache, and even more grateful because you offer free support for a free plugin that could be sold for a lot of money since we all need it, and the quality is so good.

    Any help in solving this problem would be appreciated greatly.

      1. Yes. Version 2 is what I’ve been using, but since the release of WordPress 3 I can no longer keep the logins or database cache unique for the single blog installations in memcached using:

        global $blog_id;
        $blog_id = ‘www_domainname_com’;

        I suspect there was a change made when WordPress MU was integrated into the WordPress 3 release, but I haven’t found any documentation that discusses the change. I also don’t keep up on all the core code changes so I’m left at a disadvantage in solving this issue.

        It would be nice if WordPress would offer some sort of help page to reliably plugin Memcached, APC, Xcache, and eAccelerator, so that a drop-in plugin could be used rather than a full fledged WordPress plugin. Some of us need to utilize solutions to help WordPress scale just like WordPress itself does, but so far WordPress hasn’t documented much that could be helpful for someone with more than a lightly trafficked blog. If I were more competent in this area I would provide the documentation myself on nerdgrind.com, but I have other personal family obligations that limit my time right now.

        If WordPress could officially provide more support and documentation in this area it would benefit a lot of people in my situation, while also giving people like me the freedom to use a great plugin like Super Cache, which really is Super.

      2. I went back over everything and now have Memcached working with WordPress 3.0.

        I used the drop-in plugin located at:


        Reinstalled the latest PECL version at:


        and I use this version of Memcached rather than the RPM version for RedHat:


        To make sure all objects are stored with unique identifiers in Memcached I add the following lines to wp-config.php:

        global $blog_id;
        $blog_id = ‘www_mydomainname_com’;

        I also added two more lines for good measure in case I want to add more Memcached servers in the future:

        global $memcached_servers;
        $memcached_servers = array(‘default’ => array(‘’));

        Currently Memcached runs on the same server as the MySQL server, and manages to reduce the server load significantly even though caching is also enabled in MySQL.

        I am also back to using WP Super Cache, which allows more flexibility for me than W3 Total Cache (W3TC).

        My biggest complaint with W3TC was how it utilized Memcached. The drop-in plug for WordPress listed first above has a 99% hit efficiency storing three times more items than W3TC, and uses barely any RAM whereas W3TC filled up all the RAM space storing the same objects as the drop in plugin while only getting a maximum 80% efficiency.

        Life is good again.

        1. Wow, that’s a lot of work but thanks for documenting it. You shouldn’t need to set the blog_id though. It’s set in wp-settings.php. I’ll ping Ryan about this.

  20. Hi Donncha, I noticed that even though I have Super Cache in ON mode and both Preload Cache and Super Cache Compression enabled, there are no Gzipped pages/posts/feeds served to either my browser (logged out) or services like http://www.whatsmyip.org/http_compression/ and http://ismyblogworking.com/ ( but it does detect “WP Super Cache is active.” 😉 )

    I checked the /cache/ folder and all .gz page/post files (except feeds!) are there and have the proper content. The shared server has zlib.output_compression installed but it is turned OFF for my domain. All .htaccess rules are in order as far as I can tell.

    What else could be interfering ? Thanks for your thoughts 🙂

  21. I am really batteling to reinstall wp super cache – keep getting an error message saying it it broken, I have done everything the forums have suggested to fix it but to no avail, worked perfectly fine on my other site. Please can someone urgently help. Been struggeling now for 3 days. thanks


  22. Hi Donncha, Thanks for a professional and highly effective plugin. Been using it for a few weeks so about time I sent a few token spondulix your way – done just now $xx.76 and long overdue.
    Does No Adverts for Friends work with SC, and if so – how?
    What causes some posts to be cached under WP-Cache?
    Why does compression sometimes not appear to be working – as reported by ismyblogworking.com
    Switching compression off and back on again appears to resolve it

    Go raibh míle maith agat,

    1. Danny, thanks very much for the donation! It’s much appreciated!

      1. It does, just enable the plugin of the same name in the admin page.
      2. Users who leave comments, are logged in, or use a mobile client will get wp-cache pages.
      3. Not sure why. Have you tried the debug system in the plugin to figure it out?

  23. The home page does not refresh for non-logged-in users when preload mode is checked, and a new post has been posted.

    WP Cache and Super Cache enabled
    Mobile device support (selected)
    Preload mode (selected)
    Refresh preloaded cache files every 0 minutes.
    Super Cache Compression (enabled)

    Garbage collection every 86400 seconds.

    1. Todd – worked for me. The post I just made appeared immediately in a logged out browser. I made sure the browser had loaded the homepage a few minutes previously just to be sure it was cached.

  24. The script that says ‘Currently caching from x to y post’ is getting stuck sometimes.
    I have around 1250 posts. The preloading takes some 20 mins for 1200 posts to complete and then it hangs on between 1200 – 1300. I waited half an hour and it still reads currently caching from 1200 to 1300 posts.
    I want to know if something happens if I log out of wordpress when this job is running and the reasons why this could be happening?
    Thanks for this wonderful plugin.


    1. Phil – chances are it stalled. Sometimes the next preloading job is scheduled but somehow forgotten by WordPress. It happens occasionally but hasn’t happened to either of my main blogs in the last 2 weeks I’ve been testing it.

      1. Thanks.
        Amazingly it still reads ‘currently caching from post 1200 to 1300’ when I woke up this morning after 13 hours of sleep.
        I kept wordpress logged in all this while.
        Can I log out while this job is running, in case this happens again in future?


  25. Hello,
    I was just wondering, would WP Super Cache would create an issue with me posting to my Facebook wall not pulling the image from a post?
    Thanks in advance for your help.

  26. Works great now *thumbsup*.
    After I fixed the issue of cronjobs not running that is (occasional problem because of my host and the short timeout in wp) ^^

    I have one thing to comment about though.
    Should the feeds really be cached by default?
    And if so shouldn’t they be cleared out when a new post is published just as the frontpage and blog page? I spent an hour troubleshooting today before I saw the cache footer in my feed…
    It also seems like the caching kinda ruins the feedsmith plugin, but that may have been a one time thing.

  27. Hi Donncha and All,

    I know we’re on now, but I figure you’ll see this and consider it.

    Super Cache doesn’t handle <!–nextpage–>

    I think it would be helpful if Super Cache would cache all the pages on paged posts.

    I’m also going to request that WordPress search return paged-post results as well. Google doesn’t handle them, but Yahoo apparently does. It’s strange to me that I have to go out to Yahoo to do a search that will return the URL’s with the page numbers appended.

    If you like this idea for WordPress to add this, maybe you all could vote for it over at http://wordpress.org/extend/ideas/topic/have-wordpress-search-handle-the-wordpress-quick-tag#post-17439.

    Thanks, and peace.

      1. The source code for that link says:

        <!– Dynamic page generated in 0.910 seconds. –>
        <!– Live page served on 2010-07-09 03:58:34 –>
        <!– Compression = gzip –>

        I thought it would say it’s from Supercache if it’s cached via the plugin.

        Anyway, do you think, Donncha, that you might be able to get Supercache to cache our posts that are paged with the <!–nextpage–> WordPress quick tag? If so, that would be great!

        Thanks again.

          1. No such luck for me. I even emptied my browser cache before and between refreshing. The source still didn’t show it was being serve by the plugin. I use Opera 10.60 (on Windows XP) if that helps. I also just went and checked at my own blog just to be sure my browser is still being served Super Cache pages. It is.

            Hello, I just tried it with Chrome. I get a cached page. When I come back and try it with Opera, it’s not cached even if I clear the browser cache and reload twice.

            Yep, I double checked, and your page isn’t serving a cached page to my Opera browser.

            I hope this helps you somehow, since you put in so much work on the plugin.

            Thanks for the back and forth, and I do look forward to caching the quick-tag post-pages if possible.

            WordPress “Ideas” says that my idea of returning search results directly on the post-page is under consideration. If you haven’t voted for it over there, would you do that please. You have some well deserve/earned clout there too I understand, so if you can put in a word….

            Thanks again.

          2. Tom – something odd about Opera then. I haven’t used that browser on a desktop machine in ages so maybe you can test it for me?

            Enable the debug system in the plugin, limit it to your own IP and visit your blog. It should give you a hint as to why it failed.

  28. I did as you suggested, but I want to be clear that it has been working just fine with Opera on my blog. Anyway, I used the email method rather than file. With one loading of the blog, it sent 38 emails. If you send me an address, I can forward them. Tomorrow, I can try the file method to consolidate the info for you and simply attach it to an email — whichever would work better for you. I wouldn’t want all that cookie info out in the clear here. I trust you understand.

    In the interim, I might try a few Opera-setting tweaks on your multi-page comment post.

  29. Well, I turned off the ram and browser cache and masked Opera as Firefox and turned off the new Opera feature called application caching. It still didn’t work on your comment page 8. It was worth a try though, I think, as part of the process-of-elimination.

  30. I tried to use the plugin but the admin page insisted that I make several modifications to my site, which I was not comfortable doing. So I deactivated it and tried to delete the plugin but deleting it failed, giving me these error messages:

    Warning: include(../../../wp-load.php) [function.include]: failed to open stream: No such file or directory in /home/content/44/4452544/html/wp-content/plugins/wp-super-cache/uninstall.php on line 8

    Warning: include() [function.include]: Failed opening ‘../../../wp-load.php’ for inclusion (include_path=’.:/usr/local/php5/lib/php’) in /home/content/44/4452544/html/wp-content/plugins/wp-super-cache/uninstall.php on line 8

    UNINSTALL_WPSUPERCACHE must be set to a non-blank value in uninstall.php

  31. Hi I’ve installed the plugin ( on my WP 3 site and keep receiving this error when testing the cache.

    The pages do not match! Timestamps differ or were not found!

    I’ve set debugging to ‘file’ but the entries are numerous and don’t suggest an error that I understand.

    My site has 14,000 posts and keeps getting taken down by the shared server operator for using too many system resources. So I really need this plugin to work. Please can you suggest a solution – I’ve searched high and low on the web for two hours now, to no avail.


    1. OK have just installed on another new site with only 7 articles and again, same error. It seems like this is normal behaviour for this plugin, if so it would just be nice to know. ANyone?

      1. John – it’s not normal. Unfortunately you’ll have to figure out why it’s not caching. There are loads of tips in the readme.txt and the debugging file will help if you take some time to read through it.

  32. Hi, trying to figure out how to reset the cache after saving menu (WP3.0 menu)

    tested without success the following in wp_cache_phase2

    add_action(“admin_menu” , ‘ prune_super_cache’ );

    any idea ? this would be nice to avoid the extra step of manually clearing the cache after editing

  33. OK tried this one

    add_action(“wp_update_nav_menu” , ‘ wp_cache_clear_cache’ );

    reacts OK but error message :
    Warning: call_user_func_array() [function.call-user-func-array]: First argument is expected to be a valid callback, ‘ wp_cache_clear_cache’ was given in /home/polewest/www/wp-includes/plugin.php on line 395

  34. Is there any reason for the comment in the source to say ‘Dynamic page generated in -0.83 seconds’
    Note the ‘minus’ sign.
    Duplicate process: I’ve updated a previously cached post and visited (almost immediately) it on a different browser with no cookies or history.
    When I visited that page after a minute or so, it is showing the same ‘-0.83 seconds’.
    All other pages are showing a positive number (that is with no sign at all).

    1. Todd – that’s some weird server you’ve got there, heading back in time and all that! I don’t know why you’d get a negative number there as it’s a counter and can’t be negative! You might have to dig into the source and find out for yourself.

  35. Hi Donncha,
    Am I correct in thinking that SC does not automatically generate a new cached home page after a new post is posted?
    If it does not, that may be an enhancement to consider. Google arrives usually within 30 seconds of being pinged and it would be great if it met a cached home page and a cached page for the new post.
    Many thanks,

    1. Yes, it doesn’t. You can write a plugin that hooks into the publish_post action and fetches the front page of your blog if you really want it to be cached immediately.

  36. A couple of questions (any help is appreciated):

    1. I’m seeing this error under “Directly Cached Files”. Warning! /xxx/xxx/xxx/xxx/xxxxx/
    domains/exampledomain.com/html/ is writable. Please make it readonly after your page is generated as this is a security risk.

    Since I have the CHMOD set to 750, I believe the permissions are correct. Any thoughts? (Note: x’s were just added to mask the path.)

    2. If I want to disable the mobile support, which part of the mod rewrite rules should be removed?

    3. I’ve also got the following in my .htaccess and I’m wondering if any of these would conflict with the plugin:

    #AddHandler application/x-httpd-php5 .php

    AddHandler php5-script .php

    Header unset ETag
    Header unset Last-Modified

    FileETag none

    Header set Expires “Mon, 27 Dec 2010 20:00:00 GMT”
    Header set Cache-Control “public, no-transform”

    php_value output_handler ob_gzhandler

    AddOutputFilterByType DEFLATE application/x-javascript text/css text/html text/xml

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