WordPress Thumbnails Not Working?

If you’ve upgraded your WordPress installation (or you’re new to WordPress) and you’re trying to figure out why you sometimes get thumbnails and others you don’t, then read on.

Just a little piece of advice/information that may save someone some time.

Since starting to be a bit more active with my blog, I’ve tried to upload images and sometimes I was getting thumbnails and sometimes I wasn’t. This has resulted in more than a few harsh words as I’ve struggled to understand exactly whats going on with it.

Finally I’ve got it sorted.

First off, there is a limit on the size of the source picture… if its more than 3MP WordPress won’t generate a thumbnails by default. So thanks to these threads on the WordPress support site, I got pointed in the right direction.

After much tweaking and fiddling, I found that the thumbnail generator was dieing when it tried to load the original file. No errors, no warnings, just insta-death of the thumbnail maker, so I got to thinking about memory usage.

Having checked out my servers php.ini, I found it had an 8M limit on memory usage (the default I think). I just doubled that, restarted Apache and all my images get thumbnails.


  • jfgrissom says:

    Hi Athena,

    thanks for the post… very good information…

    I have the same problem with thumbnails not being generated… but my memory is set to 64MB the variable inthe PHP.ini file is memory_limit.

    do you know of any other causes?

    Thanks for the great post…!


    • Hi Jay,

      I’ve been experiencing quite a few permissions issues with WordPress since I upgraded my server to run PHP 5. There are a lot more ‘security’ features present in PHP 5 which prevent things like the Apache user (which is used to run the scripts by the Apache webserver) accessing directories it doesn’t own etc. To get WordPress to work properly in all respects I had to change ownership of all the scripts and directories so they belonged to the Apache user and group, but this caused other issues (namely I couldn’t copy the files for backups etc.).

      I’ve since tweaked the ownership slightly such that the scripts are owned by my control panels FTP user and the Apache group and so far, it seems good… that said I haven’t tried to upload any pictures recently.

      You also mentioned your PHP memory configuration in that it’s set to a limit of 64MB… but did you also spot the statement about the 3 mega-pixel size limit? If you’re uploading straight from say a good digital camera, it’s possible the image blows this limit away so you may have to resize the image first before uploading it. That said, I do have some panoramas on my site which are huge (if they don’t break the 3MP limit I’d be surprised) and they got handled without a hitch.

      The best thing I can suggest is that if you are running on your own server and you’re happy to tinker with permissions, then try that. Other than that, without the access and error logs from your system, it’s almost impossible to say. If you can get those then have a look through them to see if there are any clues in there.

      Good luck, and if you do need more help, don’t be afraid to ask.



  • Kim Lloyd says:

    I am seeing the same issue where thumbnails aren’t resizing after moving to a new web server. At first I thought it was a memory issue, but even tiny ones are not being resized.

    So I am going to try to the script permissions change path, but just want to be clear on what scripts. Do you mean the wp-admin/js scripts, or the php files in that directory, or the entire wp-admin directory?

    Thanks so much!


    • Hi Kim,

      The permissions relate specifically to the scripts and directories of the WordPress installation directory and the sub-directories it contains. So, things like the wp-content directory.

      You shouldn’t have to worry about the Javascript… if it’s being served, there isn’t a problem with it. Unfortunately, it’s been a long time since this issue arose and I have to confess, I’ve slept alot and consumed more than a few alcoholic beverages in the intervening period so my memory of this is more than a little fuzzy.

      I would first check your web server logs to see if they give you any indication as to the cause of the failure.

      Hope this helps.


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