Using the Simple Image Sizes WordPress plugin

Working with custom image sizes in WordPress
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The Simple Image Sizes plugin is a simple, yet powerful WordPress plugin that helps to see what image sizes have been set, to set new image sizes and to (re)generate the image sizes.

This is an ongoing post. Please suggest corrections, explanations, etc. in the comment section at the bottom of this page.


WordPress offers effective functionality for developers to be able to use their own image sizes. The Simple Image Sizes plugin can either be used to tap into this functionality or be used in combination with image size-related functions.

The Simple Image Sizes WordPress plugin

Simple Image Sizes (version 3.2.1) is a free WordPress plugin created by Rahe. At the time of updating, it had over 100 000 active installs and an average rating of 4.5 out of 5 stars. Although the plugin hasn’t been updated for some time now, it still seems to work correctly on the latest version of WordPress (5.4.1).

Simple Image Sizes WordPress plugin

The plugin is used for generating newly set image sizes. In addition to this, Simple Image Sizes also offers supportive functionality to the default image sizes set by WordPress, built-in image sizes set by other plugins and themes and additional image sizes set by developers.

Simple Image Sizes plugin

Simple Image Sizes can be installed by simply typing its name in the search bar of the Add Plugins section. After its activation, its front end is incorporated into the WordPress Media Settings section (Dashboard -> Settings -> Media).

Using Simple Image Sizes to see what image sizes have been set

In addition to the default WordPress image sizes (i.e. Thumbnail size, Medium size and Large size), Simple Image Sizes will show built-in image sizes (set by other plugins and themes) and additional image sizes (set by the theme/plugin developer).

Simple Image Sizes Media Settings

Using Simple Image Sizes to generate new images

This is where the Simple Image Sizes plugin shines the brightest. Unfortunately, images uploaded before a new image size has been defined will have to be (re)generated to add the new size. Simple Image Sizes will do that for you.

Simple Image Sizes Thumbnail Regeneration

By scrolling down on the WordPress Media Settings section, the user will see the Thumbnail regeneration section of the Simple Image Sizes plugin. Here the user can decide exactly which images to regenerate/resize.

Options include by image public name and by post type. The user can simply make a selection and then press the Regenerate Thumbnails button at which Simple Image Sizes will start to go through the already uploaded images one by one. Unfortunately, Simple Image SizesĀ will not regenerate images that were already resized.

After the old images have been regenerated, WordPress will continue to regenerate new images each time they are being uploaded to the website. For this reason, Simple Image Sizes if often deactivated/deleted after old images have been updated.

Using Simple Image Sizes to create PHP code

The third handly feature of Simple Image Sizes is the ability to create PHP code for plugins/themes. This code is added to the (child) theme’s functions.php file and will allow the Simple Image Sizes plugin to be removed in the future, but still have the image sizes active.

Unfortunately, this functionality is not complete. To be fully operational, WordPress needs image sizes to be added with the add_image_size() function and the image_size_names_choose() function. Simple Image Sizes will only generate the PHP code for adding additional image sizes with the add_image_size() function.


Although the Simple Image Sizes plugin hasn’t been updated recently, it is lightweight and still packed with features that will prove handy to theme and plugin developers.

About the author
Renier busies himself with improving his English writing, creative web design and his websites, photoshopping, micro-electronics, multiple genres of music, superhero movies and badass series.
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