Thumbnailr

Thumbnailr is a YouTube thumbnail editor that runs in your browser. There's no sign-up, no install and no watermark. It has templates (including gaming), a Thumbnail Check (a design checklist), a Feed Test that previews your thumbnail in a mock YouTube feed, Series Mode for consistent thumbnails across a series (free for up to 3 per batch), and import from a YouTube link.

We built it and we're looking for a few adult YouTube creators to make one real thumbnail and tell us where it got in the way. Try it on a real video thumbnail and let us know what was confusing via the feedback page on our website.