A thumbnail is an image on a website representing an identical but larger graphic.
A thumbnail is a small image preview that is displayed instead of a large version. A common size for a thumbnail is 150 x 150 pixels. The thumbnails are often square, but there are also rectangular miniature graphics. The term thumbnail is mostly used for very small images. But a larger graphic could also be called a thumbnail, so long as it is a placeholder for the same graphic in a higher resolution.
This can be explained, for example, using the media library of the WordPress content management system. If you load an image with a resolution of 1,600 x 1,060 pixels into the media library, you can then add it in different sizes as a thumbnail, medium, large, and full size.
The standard size of a thumbnail is 150 x 150 pixels. This setting can, however, be modified in the system. If you add the image under the “large” category with a resolution of 1024 x 682 pixels, it is by no means a small picture. Nevertheless, it is a preview image, since the actual image is significantly larger.
One of the features of a thumbnail is that users can retrieve the large version by clicking the graphic. Either the larger image is displayed directly, for example in a new window, or a new page will be opened, which also contains the image. An example of this is the category page of an online shop, where the thumbnails of different product images are listed. When you click one of the product images, the details page of the product will open, containing a product description beside the larger graphic.
Thumbnails are very prevalent because of various advantages:
From a legal perspective, it should be noted that copyright protection also applies to thumbnails, even if the graphics cannot stand on their own because of their low resolution and quality. The use of thumbnails without copyright authorization and the listing of thumbnails in the Google search results is therefore legally controversial.