Most spec guides treat a wrong export as a sharpness problem. It rarely is. In the drafts we look at, a bad spec almost never shows up as a slightly soft picture. It shows up as a video that plays at two thirds of the screen, a hook line cut in half by the profile grid, or a clip that stutters in the first second while the viewer decides whether to stay.

Here is the short answer. Export every short-form video at 1080 by 1920 pixels, 9:16, at the frame rate you shot, as an MP4, and keep it under the length your platform will still recommend to strangers. That one file works on TikTok and on Instagram Reels. Everything else in this guide is about what goes wrong around that file, and which of those mistakes costs you viewers rather than pixels.

The one export that works on both platforms

You do not need a TikTok version and a Reels version. You need one master file with these properties:

Aspect ratio: 9:16, vertical. This is the only shape that fills a phone screen on both apps with nothing added.
Resolution: 1080 by 1920. Both apps deliver short-form at up to 1080p. Uploading at 4K vertical does not reach the viewer at 4K; it adds a downscale step you do not control on top of the re-encode you cannot avoid.
Frame rate: whatever you shot. Thirty frames per second is the safe default. If you shot at 24, 25 or 60, export at that rate. Converting creates frames that were never captured.
Container and codec: MP4 with H.264 video and AAC audio. It is the format both apps handle with the fewest surprises. MOV uploads fine too, but MP4 is the lowest common denominator across phones, desktop uploaders and scheduling tools.
Bitrate: high. Give the platform a clean source and let it compress. A file that was already squeezed hard in your editor has nothing left for the platform’s encoder to work with.

We covered what happens to that file after upload, and why it always looks a little worse than your export, in why your video looks worse after you upload it. This post is about the decisions you make before that point.

Length: the limit you can upload versus the limit that travels

This is where the 2026 specs changed most, and where the number on the upload screen misleads people.

Both apps now accept uploads far longer than a typical short-form video. TikTok lets many accounts upload videos well past ten minutes from the camera roll. Instagram has been extending how long a Reel can be. But the upload limit is not the distribution limit. Instagram has said Reels up to three minutes are eligible to be recommended to people who do not follow you. Longer uploads can still post, but they lose the surface that brings new viewers.

The practical rules:

If you want reach from strangers on Reels, stay at or under three minutes. Past that, you are posting for your existing followers.
On TikTok, length is a creative choice before it is a spec. The app will take a long video; the question is whether the idea earns every second. Our per-format bands are in the ideal TikTok video length is a format question.
Do not pad a video to cross a threshold. A thirty-second idea stretched to sixty-one seconds loses more in retention than the extra length is worth. The shape of that loss is in retention benchmarks by video length.

Limits roll out account by account and change more often than guides get updated. Check the upload screen on your own account before you plan a long video around a number you read somewhere, including here.

What gets cropped, and where

A 9:16 video is not always shown at 9:16. It gets cut down in at least three places, and each one hides a different part of your frame.

The profile grid

Instagram’s profile grid now shows posts as 3:4 portrait tiles rather than squares. A 9:16 Reel in that grid loses a band from the top and a band from the bottom. If your hook text sits near the top of the frame, or your cover frame puts the key object low, the grid tile shows the middle of your video and nothing that explains it. TikTok’s profile grid crops vertical videos to a similar portrait tile.

This matters more than it looks. A visitor who lands on your profile from one good video decides whether to follow by scanning the grid. A grid of cropped-off text reads as a grid of nothing. The cover choice itself is a separate lever, and we treated it as one in the cover frame is a second hook.

The interface layer

The frame is also covered while it plays: the right-hand action rail, the caption and username block at the bottom, the top tabs. None of that crops your pixels, but it hides them just as well. Instagram’s bottom block is taller than TikTok’s, which is why text placed for TikTok often disappears on Reels. We measured each app’s layout in the safe zone.

Previews and shares

When a video is shared into a chat, embedded, or shown as a preview in another surface, it can be cropped closer to square. You cannot compose for every preview. You can make sure the subject and any on-screen text live in the center of the frame, where every crop keeps them.

The rule that survives all three: keep the subject, the face and every line of text inside the central area of the frame, clear of the top and bottom sixth and clear of the right edge. Use the outer bands for background and motion, never for meaning.

The spec mistakes that cost retention, not sharpness

A slightly soft video still gets watched. These mistakes cost you viewers, which is why they are worth fixing first.

1. Uploading horizontal or square footage as-is

A 16:9 clip on a vertical feed plays as a strip across the middle of the screen, with bars or a blurred fill above and below. The subject shrinks to a fraction of its possible size, faces become small, and the video looks like it was made for somewhere else. Square and 4:5 clips are less extreme and still leave the viewer with a smaller picture than every video around yours.

The fix: reframe to 9:16 in your editor. If you have to use landscape footage, crop into it and follow the subject rather than letterboxing the whole frame. A tighter crop at slightly lower detail beats a sharp picture the size of a stamp.

2. A first frame that is not the video

Fade-ins from black, a logo sting, a blank title card. On a vertical feed the first frame is what a viewer sees before they have decided anything, and a black or empty frame gives them a reason to keep scrolling. It also becomes your auto-selected thumbnail more often than you would like.

The fix: start on a frame that already shows the subject. Cut every fade-in at the head of the timeline. We argue for starting inside the action in our hook guides, including visual vs verbal hooks.

3. Frame rate mismatches and stutter

Phones often record at a variable frame rate. Mixing clips shot at different rates, or exporting at a rate that does not match the source, can produce stutter, dropped frames or audio that slowly drifts out of sync with lips. Viewers rarely identify it, but they feel it, and it tends to show up in the first seconds where a talking head does most of the work.

The fix: set your project to the rate of your main footage before you edit, not at export. If a clip was shot at a different rate, conform it once and check lip sync on a phone, not on your monitor.

4. Text sized for a monitor

Text that reads comfortably on a laptop preview is often too small on a phone, and far too small once the interface covers part of the frame. Small text makes a viewer work, and a video that makes people work in the first second loses them.

The fix: check every text frame on a phone at arm’s length. If you cannot read it in one glance, it is too small or too long. More on when captions help at all in do captions increase views.

5. Exporting a different file for each platform

It sounds careful. In practice it doubles the chance that one version ships with a wrong setting, a missing caption or the old cut. The creators with the fewest spec problems export one master and upload that same file everywhere. If you cross-post, crossposting without the watermark penalty covers the one thing that genuinely has to change between uploads.

A one-minute pre-upload check

Run this on every video before it goes out. It takes less time than rewriting a caption.

Shape: is it 9:16, filling the whole screen, with no bars?
Size and rate: 1080 by 1920, at the frame rate you shot?
Length: under the recommendation limit for the platform you care about most?
First frame: does it show the subject, not black, not a logo?
Center: is every line of text and every face inside the middle of the frame, clear of the top, bottom and right edge?
Grid: crop a screenshot to 3:4 from the middle. Does the tile still make sense?
Phone check: watch it once on a phone, sound on, at arm’s length. Any stutter, any drift, any text you had to squint at?

If all seven pass, the spec is not what will decide how the video performs. That is the point of the check: it removes the boring reasons a good video can fail, so what is left to judge is the content itself.

What specs cannot fix

A perfect export of a weak opening is still a weak opening. Specs are a floor, not a ceiling. They stop a good video from being quietly handicapped; they do not make an ordinary video travel.

Once the file is right, the questions that matter are the ones about the video itself: does the first second earn the second one, where does attention drop, and does the idea deliver what the hook promised. That is where Blossom works. It scores your hook from 1 to 10 and explains why, maps where attention builds and where it drops with timestamps, and shows how the same format performs in your niche on TikTok and Instagram. It does not cover YouTube Shorts. You can start a 7-day trial (it needs a card and charges nothing before day 7) and run your next draft through it, or read the FAQ first.

Aspect Ratio, Resolution and Length: The 2026 Vertical Video Specs