Key takeaways
YouTube recommends custom thumbnails at 3840 by 2160 pixels for videos, in a 16:9 frame at least 640 pixels wide, uploaded as a JPG or PNG.
Uploads from a computer can be up to 50 MB, while uploads from a phone are limited to 2 MB for video thumbnails.
Most thumbnails are seen small, so build them around one clear subject, a few words at most and strong contrast.
Keep the bottom-right corner clear of important details, since YouTube puts the video length there.
YouTube Studio can test up to three thumbnails and titles on a video and shows the version with the most watch time to all viewers.
What you need
An image editor that handles layers and text. Free browser editors work, and so does any desktop design app you already use.
A sharp source image, ideally a still shot for the thumbnail rather than a frame grabbed from the video.
A verified YouTube channel, which you need before you can upload custom thumbnails.
Step 1: Set up the canvas
Create a 3840 by 2160 pixel canvas, which is YouTube's current recommendation for videos and scales cleanly down to the 1280 by 720 size many older guides use. Keep it 16:9 so nothing gets cropped. For Shorts, YouTube recommends a vertical 2160 by 3840 image.
Step 2: Decide on one idea
A thumbnail should show what the video promises in a single glance. Pick one idea, such as the result, the problem or the moment of surprise, and build the image around it. If you need to explain the thumbnail, the idea is too complicated for a picture that's often smaller than a postage stamp on a phone.
Step 3: Shoot or choose the main image
Faces and clear objects draw the eye. If you're on camera, shoot a dedicated photo with a strong, readable expression and good light rather than pausing the video. If the video is about a product or a result, show that thing large and in focus. Cut the subject out from the background so you can control what sits behind it.
Step 4: Build the composition
Make the subject big, filling a third to half of the frame.
Use a simple background that contrasts with the subject, such as a blurred scene, a flat color or a gradient.
Place the subject and any text on different sides so they don't compete.
Keep the bottom-right corner free of anything important, because YouTube overlays the video length there.
Leave a little space at the edges, since the thumbnail appears at many sizes and in different layouts.
Step 5: Add text sparingly
Text should add to the title, not repeat it. Use three to five words at most, in a thick, simple font, large enough to read on a phone. Add a stroke, shadow or solid block behind the text so it stays readable over any background. If the image tells the story on its own, skip text entirely.
Step 6: Push color and contrast
Thumbnails compete with everything else on the page, so raise contrast and saturation a little more than you would for a normal photo. Use one or two bright accent colors that stand apart from YouTube's white and dark interfaces, and keep your color choices consistent from video to video so viewers recognize your channel.
Step 7: Check it small
Zoom out until the thumbnail is about the size it appears on a phone, or view it on your own phone. Check that the subject reads instantly, the text is legible and the emotion or idea comes across. Also check it against both light and dark backgrounds, since viewers use both themes.
Step 8: Export and upload
Export as a JPG or PNG. If you upload from a computer, the file can be up to 50 MB, but from the phone app the limit is 2 MB for video thumbnails, so export a smaller JPG if you plan to upload on mobile. Make sure the thumbnail follows YouTube's Community Guidelines, since misleading or graphic thumbnails can be removed.
Step 9: Test two or three versions
YouTube Studio on a computer can A/B test up to three thumbnails, titles or combinations of both on a long-form video. When the test ends, YouTube shows the version with the highest watch time to everyone. You need advanced features turned on for your channel, and Shorts and scheduled live streams can't be tested.
Common mistakes
Too much text. If it takes more than a second to read, cut it.
Tiny subject. A face or object that fills only a small part of the frame disappears on a phone.
Busy background. Blur it or replace it so the subject stands out.
Low resolution. A blurry frame grab looks worse when YouTube scales it up on large screens.
Misleading images. A thumbnail that does not match the video can win clicks and lose watch time.
Frequently asked questions
What size should a YouTube thumbnail be?
YouTube recommends 3840 by 2160 pixels for videos and 2160 by 3840 for Shorts, with a minimum width of 640 pixels for videos. Use a 16:9 frame and upload a JPG or PNG.
What is the file size limit for YouTube thumbnails?
Thumbnails uploaded from a computer can be up to 50 MB. From a phone, the limit is 2 MB for video thumbnails and 10 MB for podcast thumbnails.
How much text should a YouTube thumbnail have?
Three to five words at most, in a bold font large enough to read on a phone. Many strong thumbnails use no text at all.
Can I A/B test YouTube thumbnails?
Yes. YouTube Studio on a computer can test up to three thumbnails and titles on a long-form video and shows the version with the most watch time to all viewers once the test ends.
Why can't I upload a custom thumbnail?
Custom thumbnails need a verified channel. Verify your account in YouTube Studio, then the option to upload a thumbnail appears in each video's details.