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Video spec checker for social media videos

This video spec checker tests a finished video's length, file size, dimensions and format against the limits of TikTok, Instagram Reels, YouTube Shorts, LinkedIn, Facebook Reels, X, Snapchat Stories, Threads, and Bluesky. It runs in your browser. Nothing is uploaded. Where a platform publishes no limit, the result says Unknown instead of guessing.

Works with: any finished video file whose details you can see on your computer or phone.

What it does not do: trim, resize or upload the video.

A video spec checker compares a finished video with each platform's upload limits before you post it, so a rejected upload never costs you a day. Postdom is an AI social media tool that turns your website into short videos, slideshows and posts, then publishes them. This free video spec checker covers the 9 platforms Postdom posts to.

Use the checker

How does this video spec checker work?

Choose a platform, then type the values from your exported file, or let the optional file reader fill in the browser-visible local metadata. Check the fields, then run the check.

Optional: choose a local video to read the exact file size, browser-reported MIME type, dimensions, and raw duration. The reported type may be empty or inaccurate. Nothing is uploaded.

Ready when you are

Enter the exported video's details, then run the check.

Missing input stays missing. The checker never treats a blank field as zero or a not-published rule as a pass.

A useful order

What should I fix first?

Fix the checks that fail before you look at recommendations. An Unknown result needs no fix: the platform simply publishes no number for it.

  1. 1

    Confirm the exported file

    Check the final export, not the editor timeline. The file details on your computer or phone give you the length, size and dimensions.

  2. 2

    Fix what failed

    Re-export only what the result names: format, file size, length, dimensions or frame shape. Renaming a file does not change its format.

  3. 3

    Leave Unknown as it is

    Unknown means the platform publishes no limit for that check. It is not a pass, so check the account and the platform before you post.

  4. 4

    Review the finished video

    Fitting the specs says nothing about the content itself. Watch the video once more and check it suits the platform and your audience.

Social media video specs

Social media video specs differ more than most people expect. TikTok takes videos up to 10 minutes, depending on the account. Instagram Reels take 3 seconds to 15 minutes, Facebook Reels 3 seconds to 90 seconds, and Snapchat 6 seconds to 60 seconds. YouTube counts a video as a Short up to 3 minutes when the frame is square or vertical. Threads allows 5 minutes and X 20 minutes. TikTok, Instagram and Facebook all recommend a 9:16 vertical frame.

Video size for social media

Video size for social media means two things: the file size and the frame size. Postdom takes MP4 or QuickTime files up to 500 MiB, and Bluesky caps video at 50 MB. For the frame, Facebook recommends 1,080 × 1,920 pixels, TikTok accepts 360 to 4,096 pixels on each side, Snapchat needs at least 540 × 960, and X recommends 1,280 × 720 with a 16:9 or 1:1 ratio. Run your export through the checker once per platform to see which of these it meets.

The rules behind the result

Video specs by platform

Every row below comes from the same records Postdom uses when it posts. An enforced rule can fail a check. A recommendation cannot. A limit the platform does not publish is shown as Not published, never as zero.

Destination

TikTok

7 enforced rules · 2 recommendations · 2 not-published fields

RuleValueStatus and source
Minimum durationNot publishedNot publishedOfficial source · verified
Maximum duration10 minutes (600 seconds)EnforcedOfficial source · verified
Accepted upload formatsMP4 or QuickTimeEnforcedOfficial source · verified
Minimum resolutionwidth: 360 · height: 360EnforcedOfficial source · verified
Maximum resolutionwidth: 4,096 · height: 4,096EnforcedOfficial source · verified
Recommended resolutionquality: 720p or higherRecommendationOfficial source · verified
Aspect ratio ruleNot publishedNot publishedOfficial source · verified
Account maximum can varyYesEnforcedOfficial source · verified
Recommended aspect ratio9:16RecommendationOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

Instagram Reels

7 enforced rules · 1 recommendations · 2 not-published fields

RuleValueStatus and source
Minimum duration3 secondsEnforcedOfficial source · verified
Maximum duration15 minutes (900 seconds)EnforcedOfficial source · verified
Accepted upload formatsMP4 or QuickTimeEnforcedOfficial source · verified
Minimum resolutionNot publishedNot publishedOfficial source · verified
Maximum horizontal resolution1,920EnforcedOfficial source · verified
Recommended resolutionNot publishedNot publishedOfficial source · verified
Aspect ratio ruleminimum: 0.01 · maximum: 10EnforcedOfficial source · verified
Recommended aspect ratio9:16RecommendationOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

YouTube Shorts

6 enforced rules · 0 recommendations · 4 not-published fields

RuleValueStatus and source
Minimum durationNot publishedNot publishedOfficial source · verified
Maximum duration3 minutes (180 seconds)EnforcedOfficial source · verified
Accepted upload formatsMP4 or QuickTimeEnforcedOfficial source · verified
Minimum resolutionNot publishedNot publishedOfficial source · verified
Recommended resolutionNot publishedNot publishedOfficial source · verified
Aspect ratio rulemaximum width to height ratio: 1EnforcedOfficial source · verified
Recommended aspect ratioNot publishedNot publishedOfficial source · verified
Shorts qualificationorientation: square or vertical · maximum duration seconds: 180 · applies to uploads on or after: 2024-10-15EnforcedOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

LinkedIn

3 enforced rules · 4 recommendations · 1 not-published fields

RuleValueStatus and source
Destination file-size ceiling5 GiB (5,368,709,120 bytes)RecommendationOfficial source · verified
Accepted upload formatsMP4EnforcedOfficial source · verified
Maximum durationNot publishedNot publishedOfficial source · verified
Minimum resolutionlongest side: 256 · shortest side: 144RecommendationOfficial source · verified
Maximum resolutionlongest side: 4,096 · shortest side: 2,304RecommendationOfficial source · verified
Aspect ratio ruleminimum: 0.416667 · maximum: 2.4RecommendationOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

Facebook Reels

4 enforced rules · 3 recommendations · 1 not-published fields

RuleValueStatus and source
Minimum duration3 secondsEnforcedOfficial source · verified
Maximum duration90 secondsEnforcedOfficial source · verified
Accepted upload formatsMP4RecommendationOfficial source · verified
Maximum resolutionNot publishedNot publishedOfficial source · verified
Recommended resolutionwidth: 1,080 · height: 1,920RecommendationOfficial source · verified
Recommended aspect ratio9:16RecommendationOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

X

4 enforced rules · 2 recommendations · 1 not-published fields

RuleValueStatus and source
Maximum duration20 minutes (1,200 seconds)EnforcedOfficial source · verified
Accepted upload formatsNot publishedNot publishedOfficial source · verified
Minimum resolutionwidth: 32 · height: 32EnforcedOfficial source · verified
Recommended resolutionwidth: 1,280 · height: 720RecommendationOfficial source · verified
Recommended aspect ratio16:9 or 1:1RecommendationOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

Snapchat Stories

6 enforced rules · 0 recommendations · 2 not-published fields

RuleValueStatus and source
Minimum duration6 secondsEnforcedOfficial source · verified
Maximum duration1 minutes (60 seconds)EnforcedOfficial source · verified
Accepted upload formatsMP4EnforcedOfficial source · verified
Minimum resolutionwidth: 540 · height: 960EnforcedOfficial source · verified
Aspect ratio ruleNot publishedNot publishedOfficial source · verified
Maximum resolutionNot publishedNot publishedOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

Threads

6 enforced rules · 0 recommendations · 1 not-published fields

RuleValueStatus and source
Maximum duration5 minutes (300 seconds)EnforcedOfficial source · verified
Aspect ratio ruleminimum: 0.01 · maximum: 10EnforcedOfficial source · verified
Maximum horizontal resolution1,920EnforcedOfficial source · verified
Accepted upload formatsMP4 or QuickTimeEnforcedOfficial source · verified
Minimum resolutionNot publishedNot publishedOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Destination

Bluesky

4 enforced rules · 0 recommendations · 2 not-published fields

RuleValueStatus and source
Destination file-size ceiling47.68 MiB (50,000,000 bytes)EnforcedEvidence or verification record unavailable.
Accepted upload formatsMP4EnforcedOfficial source · verified
Maximum durationNot publishedNot publishedOfficial source · verified
Aspect ratio ruleNot publishedNot publishedOfficial source · verified
Postdom file-size ceiling500 MiB (524,288,000 bytes)EnforcedPostdom core architecture record · verified
Postdom accepted upload formatsMP4 or QuickTimeEnforcedPostdom core architecture record · verified

Format and file size

The format and file-size checks are Postdom's own upload rules and apply on every platform. Each platform's rows add its own published length, dimension and frame-shape limits. Recommendations are guidance and never fail a check.

Free video spec checker

The video spec checker is free and needs no account. Pick a platform, type the length, file size, width, height and format from your export, or let the page read them from the file on your device. Each check comes back as Pass, Fix or Unknown, and you can check as many videos as you like. Start a free trial to see the exact fix for each failed check.

Before you rely on a result

Questions about the video spec checker

Use the result to fix a finished file before you post it. It checks the file, not what is in it.

Is the video spec checker free?

Yes. The video spec checker is free, needs no account and runs in your browser. Starting a free trial adds the exact fix for each failed check, and Postdom can make the video to spec for you.

Does passing the checker guarantee my video will publish?

No. A pass means your video fits the limits on record for that platform. A platform can still reject a video because of the account, its permissions, the content or its own policy.

Does this page upload my video?

No. You can type the length, file size, width, height and format yourself. The optional file reader uses the size, reported MIME type and video details your browser shows, and sends nothing anywhere.

Why can a result be Unknown?

Unknown means the platform publishes no limit for that check, so there is nothing to test against. The checker shows the gap rather than guessing a number, and Unknown never counts as a pass.

Which destinations does the checker support?

Every destination has a tab: TikTok, Instagram Reels, YouTube Shorts, LinkedIn, Facebook Reels, X, Snapchat Stories, Threads, and Bluesky. What each tab can decide depends on what Postdom has validated for it, and that differs by destination - a row reads Unknown when no enforced bound is published, rather than guessing a pass. Postdom validates and publishes supplied finished video.

Get videos made to spec with Postdom

Postdom reads your website and makes short videos and slideshows for your business at each platform's size, then posts them once you approve each one.

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