Most of the time you cannot upload a custom thumbnail on YouTube because the channel is not phone verified, or it is verified but the feature has not switched on yet. If the button is there and the file bounces, the cause is the file or the route; if the file uploads but the video shows something else, it is a delay, a swap YouTube makes on vertical videos, or a policy removal whose email you have not read. Six problems, six fixes, and the first job is to find out which you have.
Every YouTube rule here comes from a YouTube Help page we read on 11 September 2026, the upload limits and error wording read again on 2 October 2026, and each one names its page. The custom thumbnails page has changed its numbers over the years, so older guides may print an older set. Where YouTube gives no number, we do not invent one.
WThumb comes up in the file rules section and in the questions at the end. Otherwise this is a diagnosis page.
Why can't I upload a custom thumbnail on YouTube?
One of six things is true. Match what you see to the list, then go to that section.
- The Upload file button is missing or grayed out. Not phone verified, or verified and the feature not yet live on this channel.
- The button is there but the file is refused. Wrong format, over the size cap for your device, or the wrong shape.
- It uploaded, but the video shows a different picture. A policy removal, or a vertical long-form video where YouTube swaps in its own frame on some pages.
- You changed it, and the old one is still there. Studio shows the new image; the channel page or the phone app shows the old one.
- It is a Short, and the option is not where you expect. Shorts have a frame picker in the app and a file upload in Studio on a computer.
- You saw the words Daily custom thumbnail limit reached. A per-channel cap that YouTube says varies by country or region and by channel history.
One check first: open the video signed out or on another device. If the new thumbnail is there, the upload worked and your own browser or app was showing a stale copy.
Is your account verified, and what does Feature eligibility say?
YouTube's help page on adding custom thumbnails puts the condition in one line: you can choose from the auto-generated suggestions, or upload your own if your account is verified. Its page on verifying a YouTube account lists custom thumbnails among the things verification unlocks. If you have never verified, that is your answer.
Verification, on that page, means entering a phone number and typing in a code that arrives by text or voice call. The page says a phone number can be associated with only two channels per year, and past that point you see the words This phone number has already created the maximum number of accounts. It also says that not every operator passes on texts or voice calls from Google, so if the text never arrives, try the voice call before you try another number.
Verified, but the button is still missing
This is the most common forum thread, and it has a check. YouTube's page Learn about feature access for YouTube Creators describes two levels above the default: intermediate features, unlocked by phone verification, and advanced features, which need phone verification plus either enough channel history or an ID or video check. Custom thumbnails belong to the first of those. Open YouTube Studio, then Settings, Channel, Feature eligibility, and read the status shown there. If phone verification is not recorded for this channel, do it from that page: it is recorded per channel, so a number verified on one channel does not carry to another.
The same feature access page says a Community Guidelines strike, a copyright strike, repeated spam, misleading metadata and a few other things can delay or restrict feature access, and that a restriction comes with an email. So a fresh strike can take the feature away for now, and the Channel violations card on the Studio dashboard is where to look.
YouTube rejected the file: format, size and shape rules as of today
If the Upload file button is there and the file bounces, the file is the problem. As of September 2026, YouTube's help page on adding custom thumbnails gives this set.
- Format. JPG or PNG, the two formats the page names, with nothing else listed. A WebP, a HEIC from a phone camera or an odd screenshot is safest converted to one of those first.
- Pixel size. As large as possible, the page says, because the same image is the preview in the embedded player. Recommended: 3840 by 2160 for videos, 2160 by 3840 for Shorts. Minimum: 640 pixels wide for videos, 640 pixels tall for Shorts.
- File size. It depends on the device you upload from: 2 MB on mobile for a video thumbnail (10 MB for podcasts), 50 MB on desktop for video, Shorts and podcast thumbnails. A file refused on your phone and accepted on your laptop has hit this line.
- Shape. 16:9 for videos, 9:16 for Shorts, 1:1 for podcasts. One rule catches vertical long-form uploads: the page says a vertical video with a 16:9 custom thumbnail gets an auto-generated 4:5 thumbnail in its place on the home, explore and subscriptions pages, while the custom one still appears on the watch feed, in watch history and on non-mobile platforms.
Open the file's properties or Get Info and read the format, pixel dimensions and size in MB.
Where a WThumb file sits against that list
The file WThumb gives you is a high-quality Full HD+ JPEG at 2048 by 1152 pixels for 16:9 or 1152 by 2048 for 9:16, and both shapes can be ticked in one submission. JPG is one of the two formats the Help page names, 2048 wide is above the 640 minimum, and the shape matches the placement, so there is nothing to crop. We do not publish a file size, because it varies with the picture, so check it before uploading from a phone, and if it is close to 2 MB, use a computer. On WThumb's side, new accounts get two free credits (1 credit = 1 thumbnail), no card needed.
My custom thumbnail is not showing: removed, replaced or not there yet
You uploaded, you clicked Save, Studio showed the new image, and the video shows something else. Three explanations, told apart by where you look.
Removed under the thumbnails policy
YouTube's Thumbnails policy page lists what is not allowed: pornographic imagery, sexual acts and other sexually gratifying imagery, nudity, imagery that depicts unwanted sexualisation, violent imagery meant to shock or disgust, graphic blood or gore, vulgar or lewd language, and a thumbnail that misleads viewers about what is in the video. The page says the list is not comprehensive.
Two outcomes matter. A removal without a strike: the policy page says a thumbnail may be unsuitable for all audiences without breaking Community Guidelines, and then YouTube may age-restrict the video or remove the thumbnail, tells you, and lets you upload another. Or a removal with a strike, which brings an email and an entry on the Channel violations card on the Studio dashboard. Either way there is a message, so search your inbox first. YouTube's appeals page says a removed thumbnail is appealed through the form in that email, for up to a year after the removal.
The custom thumbnails page adds that repeat offences can cost you custom thumbnail privileges for 30 days, or the account itself, which explains a button that used to be there and is gone.
Replaced on some pages because the video is vertical
If the channel page shows your custom image, the home feed shows a frame from the video, and the video is vertical long-form rather than a Short, this is the 4:5 rule from the file section, not a fault, and there is no setting to turn it off.
Not there yet
The third, and most common: the change has not reached the page you are looking at, which YouTube says may take time, and why a YouTube thumbnail keeps changing covers how to check it and why not to upload again meanwhile. If Studio still shows the old picture when you reopen the video, nothing was saved, and the steps to add a custom thumbnail cover every route.
For the first, reading the notice, appealing a removal that is wrong and replacing the image when it is not, the thumbnail was removed is the page. What a swap does and does not reset, once it lands, is in does changing a YouTube thumbnail affect views.
Why can't I change the thumbnail on my YouTube Short?
Because Shorts have two thumbnail routes on two different YouTube Help pages, and the one you are trying is probably not the one offered where you are.
Route one is a frame picker in the YouTube app. YouTube's Create YouTube Shorts page says you can choose a frame from the Short as its thumbnail before or after upload, and that the thumbnail can be edited only from the YouTube app, not from Studio. After upload the route is your channel page, Your videos, More on the Short, then Edit.
Route two is a file upload, on a computer. YouTube's custom thumbnails page says custom thumbnails for Shorts are currently available to add only in YouTube Studio on a computer, that the account must be verified, and that the shape is 9:16. The route is YouTube Studio, Content, the Shorts tab, open the Short, and under Thumbnail click Upload file, then Save.
So the app has no Upload file button; it only offers frames. In Studio on a computer with no Upload file under the Short, the first check is verification, as for any video. If the channel is verified and the button is still missing, the Help page gives no further condition; its word is currently, the language of a feature still reaching channels. Use the frame picker in the meantime and check Studio again later. What the 9:16 image can and cannot do once it is set is in change a YouTube Shorts thumbnail.
Daily custom thumbnail limit reached: what it means and what to do
This is the most confusing error, because the number is never printed. YouTube's Add custom thumbnails page puts the rule in two sentences (YouTube Help, October 2026): "There's a limit to how many custom thumbnails a channel can upload each day. If you get an error saying 'Daily custom thumbnail limit reached' when trying to upload a thumbnail, try again in 24 hours."
The same section goes on: "Limits may vary by country/region or channel history. Copyright strikes may impact channel history eligibility. Community Guidelines strikes will affect how many custom thumbnails you can upload."
The feature access page adds one more piece: advanced features, which come from channel history or an ID or video check on top of phone verification, include higher daily upload limits, given as an example rather than a table. It does not say whether that covers thumbnails, so we will not say it does. What the two pages support together: the limit exists, it is per channel, and it moves with channel history and strikes.
Every upload counts, including ones made while trying to force an update, which is why a change that has not shown yet is a reason to wait, not to upload again. If you are setting thumbnails on a backlog of old videos, spread the work across days. The limit is not a file problem, so re-encoding the image will not help; the fix is the calendar.
