Any Shape in the App, 9:16 by API: The Facebook Reel Size Meta Publishes

What size is a Facebook reel?

Meta's recommended Facebook reel size is a 9:16 vertical video at 1080 x 1920 pixels, with 540 x 960 as the minimum, according to the Reels Publishing API, while the Facebook Help Centre says reels made in the app can be any length and any aspect ratio. The two answers come from two routes, and the route decides which one applies to your video.

The Help Centre article "Create a reel on Facebook" carries a September 2025 update: "Facebook has unified all video uploads under the Reels format. All videos posted to Facebook will be shared as reels, regardless of length or orientation." Further down, the same article puts it in five words: "any length, any aspect ratio."

The developer documentation for the Reels Publishing API, which apps use to publish reels to Facebook Pages, keeps a fixed spec table.

Spec	Reels Publishing API	Facebook Help Centre
Aspect ratio	9 x 16	Any aspect ratio
Resolution	1080 x 1920 recommended, 540 x 960 minimum	Not published
Frame rate	24 to 60 frames per second	Not published
Length	3 to 90 seconds	Any length
File type	.mp4 recommended	MP4 or MOV recommended
File size	Not published	Not published

Can a Facebook reel be horizontal?

A Facebook reel can be horizontal when you post it in the Facebook app or on facebook.com, because Meta now shares every video as a reel "regardless of length or orientation." A 16:9 video posted to your profile or Page becomes a reel without being reshaped.

Through the Reels Publishing API, the answer is narrower. The spec table lists one aspect ratio, "9 x 16." The error table on the same page widens it: error 1363040 reads "Aspect ratios for videos need to be between 16x9 and 9x16." Meta's page names a single ratio in one place and a range in another, and does not say which one the upload check enforces.

Use 9:16 for any reel that goes through the API. It matches the spec table, sits inside the error table's range, and fills a phone screen in the Reels feed. Meta's ad specs for Reels placements recommend 9:16 as well.

Which route is the reel taking?

Posted in the Facebook app

• Any aspect ratio
• Any length
• A 16:9 video becomes a reel without reshaping

Published through the Reels Publishing API

• Use 9:16 at 1080 x 1920
• Keep it between 3 and 90 seconds
• Error 1363040 covers ratios outside 16x9 to 9x16

What resolution does a Facebook reel need?

A Facebook reel published through the API needs a resolution of at least 540 x 960 pixels, and Meta recommends 1080 x 1920. Both figures are in the Reels Publishing API spec table and repeated in error 1363127: "Minimum resolution is 540 x 960 pixels. Recommended resolution is 1080 x 1920 pixels."

Meta's sample error response for a low-resolution upload words the same rule differently: "Resolution too low. Video must have a minimum resolution of 540p."

The Help Centre gives no resolution for reels made in the app. Export at 1080 x 1920 anyway. It is Meta's own recommended figure, and the same file then meets the 9:16 frame most other short-video networks use, which our guide to vertical video dimensions lays out side by side.

What frame rate does a Facebook reel need?

A Facebook reel published through the API needs a frame rate between 24 and 60 frames per second, and a fixed rate rather than a variable one. The spec table's video settings list "Fixed frame rate" and "Progressive scan," and error 1363129 states: "Reels frame rate must be between 24 and 60 frames per second."

Screen recordings at 15 FPS fall outside the range, and phone footage recorded at a variable frame rate does not meet the fixed frame rate setting. Set a fixed 30 FPS export, or a fixed 60 FPS for fast motion.

How large can a Facebook reel file be?

Meta publishes no file size limit for Facebook reels, either in the Help Centre or in the Reels Publishing API documentation. The API page mentions file size only in its upload steps, where the file_size header is set to the size of your file in bytes, and in a PartialRequestError that tells you to "Check the file size and try the upload again."

Without a published cap, length and bitrate decide the file size.

Which file format and codecs should a Facebook reel use?

A Facebook reel should be an .mp4 file with H.264 or H.265 video and AAC audio, which is what Meta's Reels Publishing API recommends. The spec table lists these settings:

• File type. .mp4 recommended.
• Video compression. H.264 or H.265, with VP9 and AV1 also supported.
• Video settings. Chroma subsampling 4:2:0, closed GOP of 2 to 5 seconds, fixed frame rate, progressive scan.
• Audio. AAC Low Complexity, stereo, 48kHz sample rate, 128 kbps or higher.

The Help Centre's article on video formats is broader: "We recommend using the MP4 or MOV format," followed by a list that includes mkv, avi, wmv and others. That list covers videos posted in the app. For reels published by an app or a scheduling tool, follow the API table.

How do you export a Facebook reel at the right size?

Export a Facebook reel at the right size by matching the Reels Publishing API spec, because a file that passes the API also works in the app. This sequence covers every row of Meta's table:

1. Set the canvas to 1080 x 1920. That is 9:16 at Meta's recommended resolution, well above the 540 x 960 minimum.
2. Set a fixed frame rate of 30 or 60 FPS. Turn off variable frame rate in the editor or the phone camera.
3. Keep the cut between 3 and 90 seconds if the reel will be published through the API. Error 1363128 reads "Reels duration must be between 3 and 90 seconds."
4. Export .mp4 with H.264 video and AAC audio at 48kHz in stereo.
5. Keep text and faces away from the edges. Facebook's interface sits on top of the full-screen player. Our guide to social media safe zones maps the covered areas.

The API also counts reels, separately from size: Meta limits it to "30 API-published posts within a 24-hour moving period." For when a reel is the right Facebook format at all, see balancing Facebook formats, and for the in-app steps, how to post reels on Facebook.

How does AdaptlyPost handle Facebook reel size?

AdaptlyPost schedules Facebook Reels to connected Pages, and it does not resize uploaded media, so each reel has to be uploaded at the size and format Facebook requires. You upload a vertical video, add a caption and set a publish time in the Facebook post scheduler, next to the Page's photos, videos and posts.

Through the AdaptlyPost API, a reel is a VIDEO post with facebookConfigs.postType set to REEL, with an optional videoTitle, and uploads accept video/mp4 and video/quicktime. The request details are in the guide to posting to Facebook via API. Bulk scheduling takes video files in MP4, MOV or WebM up to 1GB each and between 3 seconds and 5 minutes. A 1080 x 1920 MP4 at 30 FPS fits every one of those routes.

Frequently asked questions

What is the best Facebook reel size?

1080 x 1920 pixels in a 9:16 frame. Meta lists 1080 x 1920 as the recommended resolution in its Reels Publishing API and 540 x 960 as the minimum. The same export works for reels posted in the app.

Can Facebook reels be horizontal?

Yes, in the app. Meta's Help Centre says all videos are shared as reels "regardless of length or orientation." Through the Reels Publishing API, use 9:16, the ratio in Meta's spec table.

What is the minimum resolution for a Facebook reel?

540 x 960 pixels through the Reels Publishing API. A lower-resolution upload returns error 1363127. The Help Centre publishes no minimum for reels made in the app.

What frame rate should a Facebook reel use?

A fixed rate between 24 and 60 frames per second. Meta's API lists "Fixed frame rate" in its video settings and returns error 1363129 outside that range. Export at a fixed 30 or 60 FPS.

Is there a file size limit for Facebook reels?

Meta publishes none. Neither the Facebook Help Centre nor the Reels Publishing API documentation states a maximum file size for reels. Length and bitrate decide the file size instead.

What file format do Facebook reels need?

Meta's Reels Publishing API recommends .mp4 with H.264 or H.265 video and AAC Low Complexity audio at 48kHz. The Help Centre recommends MP4 or MOV for videos posted in the app. The AdaptlyPost API accepts MP4 and QuickTime files for Facebook reels.

How long can a Facebook reel be?

Through the Reels Publishing API, a reel must run between 3 and 90 seconds, and error 1363128 rejects anything outside that range. The Help Centre says reels made in the app can be any length. Keep API reels within 90 seconds.

How many Facebook reels can I post through the API per day?

Meta limits the API to 30 API-published posts within a 24-hour moving period. The cap counts posts, not file size. Plan your schedule around that count.

Which codec should I use for a Facebook reel?

Use H.264 video with AAC audio. Meta's Reels Publishing API lists H.264 or H.265, with VP9 and AV1 also supported. Audio should be AAC Low Complexity, stereo, 48kHz, 128 kbps or higher.

Does AdaptlyPost resize videos for Facebook reels?

AdaptlyPost does not resize uploaded media. It schedules Facebook Reels to connected Pages, so upload each reel at the size and format Facebook requires, such as a 1080 x 1920 MP4 at 30 FPS. Bulk scheduling takes MP4, MOV or WebM files up to 1GB each.