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What is a thumbnail?

A thumbnail is a small image representation of a larger image, usually intended to make it easier and faster to look at or manage a group of larger images. Graphic designers and photographers typically use this term.

For example, software that lets users manage multiple images often provides a miniaturized version of each image so that they don't have to remember the file name of each image.

A thumbnail also means a small and approximate version of a full-size image or brochure layout as a preliminary design step. This is also referred to as a preview image and is a smaller version of the original image.

Why are thumbnails used?

If someone has a lot of images to look through, thumbnails can help them find an image they want faster since they don't have to open each file individually.

For example, Adobe's Acrobat Reader lets users show a sequence of thumbnails of viewable pages as a way to navigate among the pages in a PDF document.

Webpages with many pictures, such as online stores with visual catalogs, also often provide thumbnail images instead of larger images to make the page download faster. Then the user controls which images need to be seen in full size.

When searching for images on a search engine, the website will return thumbnail versions of images to make scanning and scrolling through images more accessible.

Thumbnails displayed on a tablet screen
Example of thumbnails for an online video streaming catalog.

What size are thumbnails?

The thumbnail size can vary depending on the purpose. For example, thumbnail images used to represent several larger images, such as in document management software, can be very small because the focus is only on seeing which image is which.

But thumbnail images shown instead of full-size pictures on websites need to be large enough to be helpful yet small enough to download quickly.

The image format for a thumbnail can be either JPEG, PNG, GIF or WEBP. JPEG is used most often because it's smaller in file size than other image formats; however, exact pixel dimensions can vary.

Different applications for thumbnails

The following is a list of use cases for thumbnails.

  • Video thumbnail. A thumbnail for a video is a single frame or a short sequence of frames from the video. It can be used as a still image to represent the video on websites and social media.
  • YouTube thumbnail. A thumbnail on YouTube is a reduced-size version of the YouTube video's preview image. The thumbnail image represents the video content on the YouTube channel and in search results. YouTube also lets users create custom video thumbnails.
  • Blog thumbnail. A thumbnail image used in blog posts or articles is typically much smaller than the original image. The thumbnail image helps readers identify the topic of the article.

See also: digital asset management, version control, image metadata, image content search, image map

This was last updated in June 2022

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