How to regenerate older thumbnail sizes for WordPress featured image registered size

Plugin Reviewd by iTg

So, we have released our second plugin WP Category Post Lists and I hope it serves you well. One thing about the plugin is, it uses WordPress’ default featured image to show the thumbnails. As discussed previously, you can register any size of images you want. While uploading the image, WordPress will automatically check for registered sizes and will crutch the image accordingly.

But, what if you register a new image size? Will the older one get cropped automatically? The answer is NO. It won’t. When you try to get the image size then WordPress will show a proportionate HTML resized image of the original or last cropped image. So, what is the solution for that?

Thanks to Alex, a.k.a Viper007, who has provided an excellent solution for this. He has released a plugin called Regenerate Thumbnail which go to the past and resizes all the attachments to the registered sizes.

  • It works good for default sizes set from the Admin » Media.
  • Also works good for custom sizes registered via add_image_size.

So, the next time you see your thumbnails not being displayed properly, all you need to do is install and run this cool plugin.

Plugin Homepage | Plugin on WordPress directory

Also, if you are using WP CPL, then I recommend you to run this plugin atleast once after setting the thumbnail size. If you ever change the thumb size, then also it is required to run Regenerate Thumbnail.

Note that, WordPress does fine if the size is already generated via another image settings and you don’t need to worry if reverting back to a previous size. It is needed only for newly added custom sized thumbnails.

# Using the plugin:

Very very easy:

  • Install the plugin. You can either download and FTP it or search for Regenerate Thumbnail from Admin » Plugin » Add New.
  • Now go to Regen. Thumbnails from Admin » Tools.
  • Hit the Regenerate Thumbnails button.
  • This will take you to a new page. Wait a little bit there until the progress bar reaches 100%.

And you are done. The best part is, the whole process is done via several AJAX requests. So, no more run time error for a huge number of images. It will simply work fine.

Hope it was useful for you! If so, don’t forget to comment on the authors page.


  1. Free Logo Design

    I’m on my computer right now that has internet and I downloaded a game that I want to be able to play on my laptop but I don’t have the internet hookup for my laptop yet. Would it be possible to use my flashdrive and transport the game from this computer to the flashdrive to my laptop?

  2. Sara

    Hi there – thanks for this awesome awesome awesome plugin!!!! One question – my theme auto pulls the first image from each post and sets it as the featured image, so I don’t have to manually set a featured image for each post unless I want to.

    I noticed that the plugin is not auto set-up to pull the first image as thumbnail. Is this possible to enable on the settings (maybe I’m missing it!)?

    If not currently doable, you may want to consider adding this as a feature when you update the plugin – it would be very helpful for those of us who use a desktop blog publishing software (for instance – Windows Live Writer does not currently support setting a featured image for each post), so to add a featured image to a post I have to actually log in to WordPress online rather than use the desktop blog client. Just an FYI in case you didn’t realize this hiccup. Regardless, this is a great plugin! And I really appreciate your effort and generosity in sharing it with everyone. 🙂


  3. ummerlinhila

    Great article, I just given this onto a co-worker who was doing a little research on that. And he in fact purchased me lunch because I discovered it for him

    • Sharpeshots Photography

      That’s great – I thought I was going to have to go back through all my old posts and re-upload images just to change all the thumbnail sizes…which obviously would have been a serious pain

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