The YouTube community post image size question has a two-sentence answer on YouTube's own page, and the second sentence is why your 16:9 thumbnail looks cropped in the feed. As of September 2026, YouTube's Create a post page says you can upload up to 10 images with your post, each up to 16 MB, as JPG, PNG, GIF or WEBP, and that it suggests a 1:1 ratio because that is how images are shown in the feed. A thumbnail is 16:9, the feed shows a square, so part of your thumbnail's width is hidden until somebody clicks.
This post gives the numbers, explains the crop, says what a teaser should show instead of repeating the thumbnail, and ends with the brief in WThumb that survives the square.
The numbers on YouTube's page
This section is the size answer from YouTube's page and nothing else; guides that add a pixel count are guessing. As of September 2026, YouTube's Create a post page says you can choose to upload up to 10 images with your post, that each can be up to 16 MB, that the file types are JPG, PNG, GIF or WEBP, and that it suggests a 1:1 ratio because that is how images are shown in the feed. No pixel width, no pixel height, no minimum. Four things to check:
- Count. Ten per post. A teaser needs one.
- Size. Up to 16 MB each. A JPEG from a thumbnail run is well inside that; a long GIF is what reaches it.
- Format. JPG, PNG, GIF or WEBP. Anything else needs exporting first.
- Shape. A suggestion, not a limit. A 16:9 file uploads; the feed shows a square of it.
GIF is on that list. Whether a thumbnail itself can move is answered in animated thumbnail and where a GIF can go; the short version is that a GIF in a post changes nothing on the watch page, because the video's thumbnail is a separate upload.
If an upload was refused, those four lines are the whole checklist YouTube publishes. The page names no rejected ratio, so match the file against the count, the size and the format first. The numbers for the video thumbnail itself are in YouTube thumbnail size and dimensions.
Why your 16:9 thumbnail is cropped in the feed
This section explains the crop: it is the shape of the feed meeting the shape of a thumbnail. As of September 2026, YouTube's Create a post page says 1:1 is how images are shown in the feed and that viewers can see the full image by clicking to expand it, and its Add custom thumbnails page says video thumbnails use an aspect ratio of 16:9, Shorts 9:16, and podcast playlists 1:1 instead of 16:9. The two disagree by design. A 16:9 file shown as a square loses width; a 9:16 file loses height. Neither page says which part is kept, so assume the middle, the only crop that treats both sides alike, and check the posted result on a phone.
What survives a center square
The three element rule is the test: one subject, one line, one ground. A subject in the middle survives the square. Two or three words stacked near the middle survive. What dies is anything that used the width: your face at the left edge and the product at the right gives the feed the ground between them. A line across the full width loses its first and last letters. A BEFORE and AFTER split loses half of each.
Example. I QUIT MY JOB in one line along the bottom edge shows QUIT MY in the feed. Stacked as I QUIT over MY JOB under your face in the middle, it shows in full.
The paper check
Cover the left and right sides of the finished thumbnail with two sheets of paper until what remains is as tall as it is wide. That is your post image in the feed. If the subject and the words are still there, post it. If a word is cut, the next section gives the teaser its own line.
What a teaser image should show
This section is about the picture itself, because the teaser has a different job. The thumbnail wins a click on the day the video appears. The teaser makes a viewer remember that the video is coming. So it keeps the subject and changes the line to when.
The subject and the date, not the payoff
Show what the video is about and when it lands, not the result. If the thumbnail says WORTH IT? beside the robot vacuum, the teaser shows the vacuum and says FRIDAY. If the thumbnail says I WAS WRONG, the teaser says TOMORROW 6PM and does not say wrong about what. A teaser that gives away the ending leaves the thumbnail nothing to promise; one that promises what the video does not deliver is the misleading line in the policy section.
A line that differs from the thumbnail
The post and the thumbnail can sit on the same channel page, so the words must differ. FRIDAY, TOMORROW 6PM, DAY 1 IS UP, PART 2 THIS WEEK: all short, all about time. Two words fit the square better than four, and they belong near the middle with the subject.
After the video is live
The image post is for before. Once the video is public, YouTube's Create a post page, read in September 2026, says you can paste in a YouTube video URL when creating a video post, so the launch post carries the video, not a second copy of the thumbnail.
A brief to paste
- Words. FRIDAY on one line, ROBOT VACUUM on the second.
- Instructions. Me holding the robot vacuum, both of us near the middle of the frame, nothing important at the left or right edges, plain dark ground.
Where the post travels
This section follows the post after you press Post, because where it shows decides who sees the teaser and in what shape. As of September 2026, YouTube's Learn about posts page says your audience can find your posts on your channel page either on the Posts shelf in the Home tab or in the Posts tab, that posts may also show up on their homepage and Subscriptions feed, and that image posts may additionally show on the Shorts feed.
Four of those are places a subscriber already goes. The fifth, the Shorts feed, is vertical, and the page does not say how a wide image is fitted there. One more reason to build the file around its center.
The post can also reach people who have not subscribed. YouTube's November 2017 blog post Expanding Community on YouTube said that a channel's most engaged viewers could see Community posts in the Home feed without being subscribed, and that creators were using posts to build anticipation for an upcoming video. That was 2017; the September 2026 page above still lists the homepage, so write the teaser for a stranger. FRIDAY alone tells a stranger nothing; ROBOT VACUUM over FRIDAY does.
On a new channel, the Posts shelf is then the second thing on the page that speaks to a stranger; the channel trailer thumbnail is the first.
Scheduling the teaser and the video
This section lines up the two dates so the teaser lands before the video and the launch post after it. As of September 2026, YouTube's Create a post page says that to schedule a post you click the down arrow next to Post and select Schedule Post, and its Learn about posts page says scheduled posts for a future publish date will be in YouTube Studio and in the Scheduled section of the Posts tab. That is where to look when a scheduled teaser seems to have vanished.
- Finish the thumbnail first. The teaser borrows its subject from it.
- Schedule the video, or the premiere. A premiere gives the teaser somewhere to point: the premiere thumbnail viewers see before the video exists sits on a watch page that is live before the video is, and that link goes in the post text.
- Make the teaser image. Same subject, the line swapped for the date.
- Schedule the post for before the video. YouTube's pages give no timing. We would post it a day or two ahead, close enough that FRIDAY still means this Friday.
- Post the video URL after it goes live. So the Posts tab ends the week with the video, not a stale FRIDAY.
The rules follow the image into the post
This section is the policy line, because the post image is judged by the same page as the thumbnail. As of September 2026, YouTube's Thumbnails policy page says images include banners, avatars, posts, and any other YouTube feature that has images, and lists among what is not allowed nudity, violent imagery that intends to shock or disgust, graphic or disturbing imagery with blood or gore, vulgar or lewd language, and a thumbnail that misleads viewers to think they're about to view something that's not in the video. The same page says that for those violations YouTube removes the thumbnail and may issue a strike.
The teaser has its own misleading line. FRIDAY cannot mislead. I FOUND IT, on a teaser for a video where you did not find it, can. Write the teaser after you know how the video ends.
Who cannot post at all
The same month, YouTube's Learn about posts page says posts are unavailable if you're using a supervised account or your channel is set as Made for Kids, and that posts are not currently available in Germany; on a Made for Kids channel, that page adds, the Posts tab is only visible to you, and you can't create new posts but can view past posts. Social Media Today reported in May 2023 that YouTube had dropped the subscriber minimum for posts, and in June 2024 that posts were open to all channels; neither YouTube page above states a threshold, so if the Posts tab is missing, check the three reasons YouTube names first.
How to do this in WThumb
This section makes a post image that survives the square. In WThumb there is no 1:1 output and no GIF, only a 16:9 or 9:16 JPEG from a brief, and for the teaser the brief can be your own finished thumbnail.
- Paste the reference, or upload one. A YouTube link (WThumb fetches only that video's public thumbnail) or a PNG, JPEG or WebP. The reference is a brief, not a template: the idea carries over, the design is new.
- Type the words, up to three lines. For the teaser: FRIDAY, then the subject.
- Ask for the middle in the instructions line. Me and the robot vacuum near the middle, nothing important at the edges. The layout is designed from the brief, so check it against the square.
- Add your photo, or leave it out. With a photo you are placed in the design; without one the result is faceless, the person in the reference removed and the space filled in the same style. Nobody else's face is ever put in.
- Tick 16:9 (and 9:16 if a Short is coming), one or two designs, and wait about thirty seconds. Two designs, one pick.
- Download the JPEG and upload it to the post. A Full HD+ JPEG is on the file type list and inside the 16 MB limit on YouTube's Create a post page, read in September 2026.
Two runs, or a revision
Two runs from one reference is the cleanest pair: WORTH IT? for the thumbnail, FRIDAY for the teaser, same photo, same instructions. If only the words need swapping, the pencil on the finished thumbnail takes one plain sentence and makes one new version: one credit per revision (1 credit = 1 thumbnail), as many revisions as you need.
No square, no GIF, two free
A moving teaser is a job for another tool; a true square means cropping the JPEG yourself, which also previews the feed. On a new account both runs cost nothing: the account starts with two free credits, no card needed.
Build the teaser for the square: subject and date in the middle, ground at the edges.
