See how your thumbnail holds up in a crowded feed

Load the image file into a preview that mocks the layouts YouTube renders it in, then read it at that size instead of at full size in your editor. This page does that in four layouts at once and pairs each with your real title. It is a mock of the interface, not a draft on your channel — nothing is published and nothing is sent to YouTube.

YouTube currently recommends 3840 × 2160 pixels at a 16:9 ratio, with a minimum width of 640 pixels, in JPG, GIF, or PNG. The video-thumbnail upload limit depends on the device: 2 MB on mobile and 50 MB on desktop. The source table above links to the YouTube Help page and shows when Kabo last checked it.

No. The file is read by your own browser through a local object URL, so it is never sent to Kabo or to any other server, and this page makes no network request with it. Close the tab and the preview is gone. There is nothing stored and nothing to delete.

Most YouTube watching happens on phones, where the thumbnail renders far smaller than the canvas you designed it on and the title stacks underneath rather than beside it. Small text that reads fine at full size turns into a grey smudge, and a face near the edge can get clipped by the crop. The mobile scene above stacks the same way so you catch it before it ships.

There is no formula, and anyone selling one is guessing. What holds up across niches is legibility at small size: one clear subject, strong contrast against a pale feed background, and at most three or four words of text. The rest is whether the image and the title together promise something a viewer cannot get by scrolling past — which is why this page always shows them together.

Smaller than anywhere else. The suggested column packs entries into a narrow strip beside the player, so that is the smallest your image will ever be rendered. Exact pixel sizes shift with window width, device, and YouTube's own layout experiments, so treat the sidebar scene above as an approximation rather than a measurement.

If YouTube's own upload screen refuses or ignores your thumbnail, check the device-specific limit first: video thumbnails must stay under 2 MB when uploaded from mobile and under 50 MB from desktop. YouTube Help lists JPG, GIF, and PNG, and custom thumbnails require an eligible verified account. A saved change can also take time to appear. If this page will not load your file, check that it is a plain image rather than a PSD or document export.

No. Adding a second image only renders both candidates in the same mocked layouts so you can compare crop, contrast, and legibility at feed size. It does not publish either image, receive live traffic, measure click-through rate, or choose a statistical winner. A real experiment must run against actual viewers through YouTube's own testing features where available.

Yes — switch the preview between Light and Dark and the scenes repaint in YouTube's dark-theme colors. It is worth checking both, because many viewers keep YouTube in dark theme, especially on phones. A thumbnail with a white background that pops against a pale feed can glare or lose its edges against near-black, and pale text that reads fine in light mode can wash out. If your image depends on a light border or bright margins, the dark scenes will show you what disappears.

It is a close mock, not a pixel-perfect copy. YouTube changes its layouts by device, by window width, and through rolling interface experiments, and the view counts in the scenes are placeholders for spacing. What it does reproduce faithfully is the part that decides the click: your image at feed scale, cropped to 16:9, with the real title next to it.