Trusted WordPress tutorials, when you need them most.
Beginner’s Guide to WordPress
WPB Cup
25 Million+
Websites using our plugins
16+
Years of WordPress experience
3000+
WordPress tutorials
by experts

What is: Thumbnail Sizes

Editorial Note: We earn a commission from partner links on WPBeginner. Commissions do not affect our editors' opinions or evaluations. Learn more about Editorial Process.

Thumbnail sizes is a built-in WordPress theme feature that allows theme designers and developers to define thumbnail sizes for images uploaded by the users. Often users confuse think that thumbnail sizes only apply to thumbnails or featured images. It is NOT true. Thumbnail sizes apply to any and all images that you upload in your WordPress. Thumbnail size is better defined as additional image sizes.

Designers and developers can choose to use one of the sizes defined in WordPress Settings » Media screen, or define their own additional image sizes. Once a new size is defined, WordPress will automatically generate a copy of each size when you upload the image. It does not automatically generate new sizes for previously uploaded images. However, there are plugins such as Regenerate Thumbnails that you can use to generate new sizes of all previously uploaded images.

There is some criticism of this feature. Critics say that this feature can consume a lot of hard disk space if you have multiple image sizes and a lot of images on your site. Unfortunately this criticism is accurate. If you have a lot of images, then you want to limit the amount of image sizes that you have on your site or simply pay for more web hosting space.

Additional Reading

Editorial Staff

Editorial Staff at WPBeginner is a team of WordPress experts led by Syed Balkhi with over 16 years of experience in WordPress, Web Hosting, eCommerce, SEO, and Marketing. Started in 2009, WPBeginner is now the largest free WordPress resource site in the industry and is often referred to as the Wikipedia for WordPress.

The Ultimate WordPress Toolkit

Get FREE access to our toolkit - a collection of WordPress related products and resources that every professional should have!

WPBeginner Assistant
How can I help you?

By chatting, you consent to this chat being stored according to our privacy policy and your email will be added to receive weekly WordPress tutorials from WPBeginner.