As a YouTube creator, you have probably come across the situation where you needed to test how well a certain thumbnail works, or whether text on it is too small. Yet, this is a pain to do, as thumbnails can take days to update, and you might need to create a private video to test on without annoying your subscribers.
This page sets out to make the whole process a lot easier by letting you select an image and preview it in all relevant dimensions and contexts. All of the processing is done client-side, nothing is stored on our end.
The recommended size for YouTube thumbnails is 1280×720 pixels. The minimum width required is 640 pixels.