Canva

Design software that runs in a browser and starts you from a template rather than a blank canvas. The YouTube thumbnail preset is already the right size and the editor takes an afternoon to learn, which is most of the appeal. Canva Pro adds background removal, saved brand colours and one-click resizing between formats. Its limitation is its strength. A template easy for you to find is easy for everybody else, and a thumbnail's whole task is to look unlike the 20 around it.