How to change a YouTube thumbnail depends on the device in your hand, and the routes are not equal. A computer can upload an image up to 50 MB, the YouTube app one up to 2 MB, and a Short takes a designed image only on a computer. The same steps add a thumbnail to a video that never had one, at upload or long after it.
Every step below comes from YouTube's own help pages, read in September 2026, with the page named. This post covers regular videos. Shorts, upload errors, automatic changes and the question of whether a new thumbnail helps each have their own post, linked where they come up.
The short answer: three routes
As of September 2026, YouTube's Add custom thumbnails page gives one route for a computer and two for a phone, and all three end in the same place: the video's Thumbnail slot. The table lines them up.
| Route | Where to go | What you can set | File limit |
|---|---|---|---|
| Computer | YouTube Studio, Content, the video's details, Thumbnail | Upload file for your own image, or Get suggestions to generate one | 50 MB, JPG or PNG |
| YouTube app | Profile picture, Your videos, More, Edit, Edit thumbnail | An auto-generated thumbnail, or Custom thumbnail for your own image | 2 MB |
| YouTube Studio app | Content, the video, Edit, Edit thumbnail | An auto-generated thumbnail, or Custom thumbnail for your own image | 2 MB |
All three ask for the same thing first. The same page says your account must be verified to use this feature, and that is YouTube's phone verification, covered in its own section below.
How to change a thumbnail on a computer, in YouTube Studio
This is the route for a designed thumbnail, because it takes the largest file. The Add custom thumbnails page lists the steps:
- Sign in to YouTube Studio.
- From the left menu, select Content.
- Go to the video you want to edit and click the edit (pencil) icon to open its details.
- Below Thumbnail, click Upload file and choose the image on your computer, or select Get suggestions to generate a thumbnail.
- Click Save.
The same page says it may take time for your thumbnail changes to appear on YouTube, and it gives no number. To see what viewers see, look at the video signed out or on a second device.
Get suggestions and Ask Studio
Get suggestions is YouTube's own generator. The same page says Ask Studio analyzes your video's transcript and themes to suggest thumbnails tailored to your video, and YouTube's post Making thumbnails easier on YouTube, dated July 24, 2026, brings thumbnail generation into Ask Studio for long form videos. How that compares with bringing your own image is in Ask Studio's thumbnail generator.
How to change a thumbnail on your phone
As of September 2026, the phone version of YouTube's Add custom thumbnails page gives the same steps for Android and for iPhone and iPad. In the YouTube app:
- Tap your profile picture, then Your videos.
- Next to the video you want to edit, tap More, then Edit, then Edit thumbnail.
- Select an auto-generated thumbnail, or tap Custom thumbnail to use an image from your phone.
- Confirm the choice and tap Select, then tap Save.
In the YouTube Studio app the path is Content, the video, Edit and Edit thumbnail, with the same two choices and the same Select and Save at the end.
One limit catches people out. The same page allows 2 MB for a video thumbnail from a phone, against 50 MB from a computer, and a large PNG from a design app is often over it. The free compressor can compress it under 2 MB: its Target 2 MB setting finds the highest quality that fits, in your browser. If you are making the image on the phone as well, make the thumbnail on your phone covers that side, and the design choices behind any new image are in how to make a YouTube thumbnail from the first decision.
How to add a thumbnail while you upload
You do not have to wait for the video to go live. YouTube's Upload YouTube videos page, read in September 2026, lists Thumbnail among the details you fill in during the upload, and describes it as the image viewers will view before choosing your video. Set it there and the video never appears with a frame you did not choose.
If you have no image ready, the video still gets a thumbnail: on a phone, the Add custom thumbnails page offers auto-generated thumbnails to select from. A frame can be enough when the video has a moment that explains itself, and a frame from the video says how to pick one that reads at feed size.
Before you can: verification
If Upload file or Custom thumbnail is missing, the account is the usual reason: the Add custom thumbnails page says your account must be verified to use this feature, and YouTube's Verify your YouTube account page, read in September 2026, makes that a phone number and a code sent by text or voice call. What to check when you have verified and the option is still missing is in custom thumbnail not working.
Shorts are different
A Short follows its own rules. As of September 2026, the Add custom thumbnails page says custom Shorts thumbnails are currently only available to add in YouTube Studio on a computer, under Content, then Shorts, and YouTube's July 24, 2026 post opens them to YouTube Partner Program creators first. On a phone you can choose a frame from the Short instead. The steps for both are in change a Shorts thumbnail after posting.
When the new thumbnail does not show
If the upload fails, whether the button is missing, the file is refused or YouTube says Daily custom thumbnail limit reached, each cause and its fix are in why a custom thumbnail will not upload. If it saved but the old image still shows, or the picture later changes by itself, thumbnail keeps changing covers the delay and the other four causes.
Should you change it, and how often?
YouTube encourages it for older videos. As of September 2026, its Thumbnail & title tips page says, "We also recommend experimenting with updating older thumbnails to increase your video's appeal to new viewers." What a swap does and does not reset is covered in does changing a thumbnail affect views.
Change one thing at a time, and leave it long enough to read. If you would rather measure than guess, YouTube's own tool, described on its title and thumbnail testing page, tries up to 3 versions of a regular video from YouTube Studio on a computer and does not run on Shorts. Test & compare covers how it picks a winner and how to make versions worth comparing.
How to do this in WThumb
The steps above change the thumbnail; the new image has to come from somewhere, and that is the part WThumb does. It does not connect to your channel or upload anything to YouTube. You make the image, check it, and set it with the steps above.
- Pick how to start. Recreate a thumbnail from a YouTube link or an uploaded reference, or start from a prompt with the video's title and what happens in it. Then choose 16:9, 9:16 or both.
- Add words and a photo. Up to three lines of words, or No text. Your photo puts you in the design; without one it is faceless, and nobody else's face is placed.
- Check it at feed size. Put the JPEG into the free YouTube thumbnail tester to see it in a home feed, search results and a phone view, light or dark.
- Upload it once. Use the computer route for the full file, or compress it first for the 2 MB phone limit, then leave it alone long enough to judge.
If the first version is close
A run takes about 30 seconds. New accounts get 2 free credits (1 credit = 1 thumbnail), no card needed. If the first version is close, revise it in words instead of starting over: the pencil on a finished thumbnail takes a change such as BIGGER FACE or FEWER WORDS, and each revision uses 1 credit.
