How to Make a YouTube Thumbnail: Size, Rules and Upload

The numbers most guides repeat are out of date. Here are the ones YouTube's help center lists now, and the steps from a blank canvas to a tested thumbnail.

Actualizado el 2026 de octubre

What is the YouTube thumbnail size?

As of October 2026, YouTube's help center lists these requirements for custom thumbnails:

• Resolution: 3840 by 2160 pixels for videos, with a minimum width of 640 pixels.
• Aspect ratio: 16:9 for videos.
• Formats: JPG or PNG.
• File size: up to 2 MB when uploading from a phone, up to 50 MB from a computer.
• Content: the image has to follow YouTube's Community Guidelines, like the video itself.

What file types does YouTube accept for thumbnails?

JPG and PNG, according to the current help page. Older guides also list GIF, which came from earlier versions of YouTube's guidance; if you have a thumbnail in another format, export it as PNG or JPG before uploading.

PNG keeps text edges crisp and suits flat graphics. JPG makes smaller files and suits photographs. For a thumbnail that mixes a photo with bold text, either works; just check the text after export, since heavy JPG compression smudges thin letters first.

Why can't I upload a custom thumbnail?

Usually because the account isn't verified. Custom thumbnails are one of YouTube's intermediate features, which unlock when you verify your channel with a phone number. Until then, YouTube only lets you choose among frames it picks from the video. How to start a YouTube channel covers verification and the other features it unlocks.

The other causes:

• The file is over the size limit for the device you're using. Try from a computer, where the limit is 50 MB.
• The format isn't JPG or PNG.
• The image is narrower than 640 pixels.
• The channel has lost access to custom thumbnails after a Community Guidelines issue. YouTube's help page warns that a thumbnail that breaks the guidelines can bring a strike, and repeated problems can remove the ability to upload custom thumbnails for a period.

How do you design a thumbnail that gets clicked?

Start from where it's seen. Most thumbnails are viewed small: in a search list on a phone, next to another video, on a TV home screen from across the room. Design for that size and it will look fine everywhere else.

• One subject. A face, an object, a result. If you need to point at three things, the thumbnail is doing the title's job.
• Few words, large. Three or four words that add to the title rather than repeating it.
• Contrast that survives shrinking. A subject that stands out from the background at the size of a fingernail.
• Honesty. A thumbnail that promises something the video doesn't deliver gets the click and loses the viewer in seconds, which shows up as weak watch time.
• A consistent look across a series, so returning viewers recognise your videos in a crowded feed.

Can you change a thumbnail after posting?

Yes, at any time. In YouTube Studio, open Content, click the edit icon on the video, upload a new file under Thumbnail and save. The change applies everywhere the video appears, although it can take a little while to show up across YouTube.

The views a video has already collected stay. Changing a thumbnail doesn't reset anything, and it's one of the few changes you can make to a published video that can revive it. Thumbnails for Shorts work differently, and how to change the thumbnail on YouTube Shorts covers that case.

Does a thumbnail affect views?

Directly. YouTube shows your video to people as an impression, a thumbnail on their screen, and the share of those impressions that turn into views is your impressions click-through rate in YouTube Studio. A better thumbnail on the same video raises that rate and turns the same impressions into more views. What impressions are on YouTube explains how they're counted.

The click is only half of it. YouTube also watches what happens after the click, which is why a misleading thumbnail rarely pays off. The thumbnail that wins is the one that brings in people who then watch.

Can you A/B test thumbnails on YouTube?

Yes, with Test & Compare in YouTube Studio. As of October 2026, YouTube's help center says you can test up to three thumbnails, or three titles, or combinations of both, on one video. YouTube shows the options to different viewers, and at the end the one with the highest watch time becomes the thumbnail everyone sees.

The limits from the same page: it's only available on a computer through YouTube Studio, it needs advanced features enabled, and it isn't available for Shorts, scheduled live streams, private videos, or videos set as made for kids or for mature audiences. Tests usually finish within two weeks, depending on how many impressions the video gets.

Results come in three kinds: a winner, a result where the options performed the same, and an inconclusive result, in which case the first option you uploaded stays as the default.

Testing only needs traffic to compare. A new video with a handful of impressions won't produce a verdict, which is part of why channels care about the first days of a video. Some give a new upload a starting count with YouTube views, which needs the video's watch link and nothing else; it changes the number shown under the video, not how YouTube ranks it or which thumbnail wins. Every YouTube service is listed on the YouTube page, and how to grow your YouTube channel covers why thumbnails and titles carry so much weight.

Questions people ask about YouTube thumbnails