Recently, a WPBeginner reader asked for our help regarding an issue with images on their website. It all started when the user switched to a new theme, and the theme displayed thumbnails next to the excerpt of the post. The problem was that all new images that were uploaded after activating the theme were looking good, but all the old thumbnails looked ugly and distorted. The user tried to adjust image sizes in Settings » Media, but it didn’t solve the problem. In this article, we will show you how to regenerate thumbnails or new image sizes in WordPress.

By default when you upload an image to WordPress, it creates different sizes and saves them in the uploads folder. Previously, we published a tutorial on how to create additional image sizes in WordPress. Many WordPress themes take advantage of this feature and define new image sizes, but the problem is that these new image sizes are only applied on the images you upload after activating the theme.

To solve this problem you need to generate new sizes for all previously uploaded images. This process is often referred to as regenerating thumbnails.

To generate images in newly defined image sizes, install and activate the Regenerate Thumbnails plugin. After activating the plugin, go to Tools » Regen. Thumbnails.

Pressing the regenerate thumbnail button will start generating new image sizes defined by your theme or in Settings » Media page. It may take a while, depending on how many images you have on your website.

You can also regenerate image sizes for selected images in Media » Library.

Regenerating images sizes does not affect your original upload. It creates additional copies of images in the newly defined sizes.

It also does not delete previously created image sizes. You can delete the sizes if you are sure that you haven’t used those sizes anywhere on your website.

We hope this article helped you learn how to regenerate thumbnails and new image sizes in WordPress. You may also want to see our guide on how to fix common image issues in WordPress.

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