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A Facebook Reel published through Meta's API must be 3 to 90 seconds long, vertical 9:16, at least 540×960 pixels (1080×1920 recommended), 24 to 60 frames per second at a fixed rate, preferably as an MP4. Reels can only be published this way to Facebook Pages, and each Page can publish 30 API Reels in a rolling 24 hours.
Facebook Reels video requirements
Property | Requirement |
|---|---|
File type | .mp4 recommended |
Aspect ratio | 9:16 |
Resolution | 1080×1920 recommended, 540×960 minimum |
Frame rate | 24–60 fps, fixed |
Length | 3–90 seconds |
Video | H.264 or H.265 (VP9 and AV1 also supported), 4:2:0 chroma, closed GOP of 2–5 seconds, progressive scan |
Audio | AAC Low Complexity, stereo, 48 kHz, 128 kbps or more |
Meta's Reels specification doesn't state a maximum file size. A 90-second 1080p H.264 file is normally well under 100 MB, so in practice the length limit is what you hit first.
The 90-second limit is the one that decides your edit
Instagram takes Reels up to 15 minutes, TikTok up to 10 through its API, YouTube files vertical videos as Shorts up to 3 minutes. Facebook's Reels API stops at 90 seconds. If one master clip is going to all four, Facebook sets the length: cut it to 90 seconds or less, or make a separate, shorter Facebook version.
When Uplonic publishes to a Facebook Page, a video between 3 and 90 seconds goes out as a Reel; a longer one is posted as a regular Page video instead of failing, so it won't appear in the Reels tab.
The minimum matters too. A 2-second loop or a very short reaction clip is below Facebook's 3-second floor (Instagram and LinkedIn have the same 3-second minimum).
Frame rate and keyframes: the settings exporters get wrong
Two of Meta's video settings are easy to miss in an export dialog:
Fixed frame rate. Phone recordings often use a variable frame rate to save battery. Re-export at a constant 30 fps if your editor offers it.
Closed GOP of 2–5 seconds. A "GOP" is the run of frames between two full keyframes. At 30 fps, a keyframe every 60 frames gives 2 seconds. Many exporters call this "keyframe interval".
The ffmpeg command in our social media video specs overview sets both (fps=30 and -g 60), along with the AAC 48 kHz audio Meta asks for.
Pages only, and who can post
Meta's Reels Publishing API publishes to Facebook Pages. It can't post Reels to a personal profile, which is why scheduling tools ask you to connect a Page, not your profile. The person connecting the Page needs a role that lets them create content on it, and grants the tool three permissions during Facebook login: showing your list of Pages, reading Page engagement, and managing Page posts.
Good to know: if a tool can't see a Page you manage, the usual cause is that the Page wasn't ticked in the Facebook login dialog. Reconnecting and selecting the Page usually fixes it, as long as your role on the Page allows you to create content there.
How many Reels per day
"Reels API is limited to 30 API-published posts within a 24-hour moving period" per Page, and Meta recommends that apps enforce the limit themselves, especially for scheduled posts. The window is rolling: a Reel published at 18:00 frees its slot at 18:00 the next day, not at midnight.
Caption length
Meta's Reels documentation doesn't give a caption limit. Uplonic trims the Facebook description at 2,200 characters, keeping the hashtags at the end. For the networks that do document their limits, see social media character limits.
Before you schedule a Facebook Reel
3–90 seconds.
9:16, 1080×1920, H.264, fixed 30 fps, keyframe every 2 seconds.
AAC stereo, 48 kHz.
A Facebook Page connected, not a profile.
Fewer than 30 API Reels on that Page in the last 24 hours.
Check the length, resolution and container in your browser with our video spec checker before you schedule.
Sources & methodology
How we got these numbers: from Meta's Reels Publishing API documentation, re-checked on October 17, 2026. Meta doesn't publish a Reel file-size or caption limit in that guide, so we don't give one.
Reels Publishing API — specifications, limits and requirements — Meta for Developers, accessed October 2026
