Every platform has a preferred video format. Upload outside those specs and the platform either rejects your file, silently degrades the quality, or forces a crop that cuts off exactly the wrong thing. It's not random. It's not a bug. It's the platform telling you - in the rudest possible way - that you did it wrong.
The frustrating part is that none of them explain this clearly in one place. You have to dig through support docs written by people who clearly haven't uploaded a video in their lives. So I did that digging. Here's what actually matters, platform by platform.
TikTok - The One That Punishes You the Most for Getting It Wrong
TikTok is a vertical video platform. Full stop. If you upload anything that isn't 9:16 (portrait orientation), TikTok will add black bars on the sides or force a crop. Either way, it looks amateur. Don't do it.
What TikTok actually wants:
Resolution: 1080 × 1920 pixels. Aspect ratio: 9:16. Format: MP4 or MOV. Maximum file size: 287.6MB for iOS, 72MB for Android (yes, the limits are different - annoying but true). Maximum length: up to 10 minutes for most accounts, though shorter videos still perform better. Frame rate: 24–60fps. TikTok handles all of these fine.
The one thing people get wrong most often: exporting at the wrong bitrate. TikTok's own compression is aggressive, so if you upload a low-bitrate file, the final result looks terrible because TikTok then compresses an already-compressed video. Export at the highest quality your editing app allows. Let TikTok do the compression from a clean source, not from a file that's already been squeezed.
Also - upload on Wi-Fi. I mentioned this in another piece and I'll say it again here: TikTok appears to serve lower quality versions of videos that were uploaded on slow mobile connections. It's not officially documented anywhere, but I've seen it consistently enough to believe it's real. Upload on Wi-Fi, especially if you're posting something you care about.
Instagram - Three Different Formats, Three Different Rules
Instagram is the most complicated one because it has multiple video contexts and each behaves differently. You've got Reels, Feed videos, and Stories. They don't all want the same thing.
Reels: 9:16, 1080 × 1920px, MP4 or MOV, up to 90 seconds. This is Instagram's main video push right now - they're prioritising Reels in the algorithm heavily. If you're creating video for Instagram and ignoring Reels, you're leaving reach on the table.
Feed videos (square or landscape): 1:1 square at 1080 × 1080px works reliably and fills the feed thumbnail well. Landscape 16:9 at 1920 × 1080px is also supported. Portrait 4:5 at 1080 × 1350px is arguably the best for feed because it takes up more screen real estate when people are scrolling - more pixels, more attention.
Stories: 9:16, 1080 × 1920px, up to 60 seconds per Story card. The safe zone matters here. Instagram overlays UI elements - your profile icon, the swipe-up area, the reply bar - over the top and bottom of the frame. Keep important content in the middle 80% of the screen. Anything at the very top or very bottom risks being covered.
Instagram's compression is notoriously bad. It's gotten slightly better, but upload something with fine text or complex motion and watch what happens. The workaround most creators use: export at a higher bitrate than you think you need, then let Instagram compress from a quality source. Some people also swear by uploading as H.264 rather than H.265, claiming Instagram handles it more cleanly. I've had mixed results - worth testing for your specific content type.
Facebook - Old Platform, Weirdly Flexible Specs
Facebook supports a surprisingly wide range of video formats, which sounds like good news until you realise that "flexible" often just means "will accept your file but still compress it into mediocrity."
What Facebook wants: MP4 or MOV, 1080p at most (though it accepts up to 4K, it re-encodes everything down anyway), 16:9 aspect ratio for standard video, up to 4GB file size, and maximum length of 240 minutes. That last one is absurd - almost no one is uploading four-hour videos to Facebook - but it's technically supported.
Facebook Reels follow the same 9:16 specs as Instagram Reels, which makes sense given they share infrastructure. Keep it at 1080 × 1920px, under 60 seconds for Reels specifically.
For regular feed videos, Facebook does reasonably well with landscape content - probably because it was designed before vertical video became dominant. If you're sharing something intended for desktop viewers, 16:9 at 1080p is still the right call. For mobile-first content, match the Reels spec.
One Facebook-specific issue: their auto-captions are inconsistent and often wrong, and a large portion of Facebook video is watched with sound off. If your video relies on audio to make sense, it's not optimised for Facebook. Either add captions manually or make the visuals carry the story.
X (Twitter) - Tight Limits That Catch People Off Guard
X has some of the strictest video constraints of any major platform, and they've gotten stricter since the API changes. If you're not on X Premium, the limits are quite tight.
Standard (free) account limits: MP4 or MOV, maximum 512MB file size, maximum 2 minutes 20 seconds (140 seconds). Resolution caps at 1280 × 720px for standard accounts. That's 720p - uploads above this resolution get downscaled.
X Premium limits: Up to 3 hours of video, up to 8GB file size, and higher resolution support including 1080p and potentially 4K for some account types. Whether that's worth paying for depends entirely on how much video content you post there.
Aspect ratio: X supports 1:1, 5:4, 16:9, and 9:16. The 16:9 landscape format tends to render best in the feed on desktop. On mobile, 1:1 square fills the preview card well. Vertical video (9:16) is supported but not prioritised the way it is on TikTok or Instagram.
X video gets watched quickly and scrolled past quickly. If your content doesn't hook in the first two seconds, it's effectively invisible. That's less a spec issue and more a content issue - but it's worth knowing before you spend time optimising resolution for a platform where retention is brutal.
Reddit - The Platform That Nobody Thinks About for Video
Reddit isn't primarily a video platform, but its built-in video hosting (via Reddit's native video player) has gotten considerably better. The problem is that Reddit's video player is still a bit awkward - no sound autoplay, inconsistent mobile behaviour, and the audio/video separation issue that plagued it for years (when you downloaded a Reddit video, audio was a separate file - a genuinely annoying quirk that downloaders like MyVideoCity handle automatically).
Reddit video specs: MP4, maximum 15 minutes for standard users, up to 60 minutes for Reddit Premium. Maximum file size 1GB. Supported resolutions up to 1080p. 16:9 tends to look best in the feed - Reddit is still primarily a landscape/desktop-first platform at its core, even if mobile usage is huge now.
One genuinely useful thing about Reddit video: subreddit-specific rules often matter more than platform specs. Some subreddits require direct video posts, some only allow links, some have length limits. Check the subreddit sidebar before assuming your video will be accepted.
Vimeo - For When Quality Actually Matters
Vimeo is where you go when you're done compromising on quality. It's the platform that won't mangle your carefully graded footage - at least not at the same rate as the others. The free tier has storage limits, but the encoding quality is noticeably better than what Instagram or TikTok will give you.
What Vimeo supports: Practically everything. MP4, MOV, AVI, WMV - it handles all the common formats. Resolution up to 8K. Aspect ratios are flexible. The recommended export settings for best results: MP4, H.264, 1080p at 10–20Mbps bitrate, stereo audio at 320kbps.
Vimeo's privacy controls are excellent - you can password-protect videos, restrict playback to certain domains, disable downloads, or allow downloads. For client work, portfolio pieces, or anything where quality control matters, Vimeo is usually the right choice over YouTube alternatives.
The Universal Rules That Apply Everywhere
A few things are true regardless of which platform you're uploading to.
Export at the highest quality your editor can produce, then let the platform compress. Never upload something you've already heavily compressed - you're compressing twice and the result looks it.
H.264 is still the most universally compatible codec. H.265 is more efficient but some platforms handle it worse. If you're not sure, H.264 is the safe choice.
Audio at 44.1kHz or 48kHz stereo is standard across all platforms. Don't overthink the audio settings - get the video right and standard audio settings will be fine.
Frame rate: whatever your source footage is, export at the same frame rate. 24fps for cinematic content, 30fps for general content, 60fps if you're doing slow motion or gaming. Mismatching the export frame rate to the source is a common mistake that introduces judder.
What to Do When You've Already Downloaded a Video and Want to Re-Upload It
This comes up more than you'd think. You download a video from one platform - through MyVideoCity, say - and you want to re-post it somewhere else. Maybe it's your own content and you want to cross-post. Maybe you have permission. What do you need to know?
The downloaded file is already compressed by the original platform. Re-uploading it to a second platform means a second round of compression. The quality loss compounds. If the original was sharp, the re-upload will be softer. If the original was already a bit soft, the re-upload will be notably degraded.
There's no fix for this if you don't have the original source file. You're working with whatever the platform kept. The best you can do is use the highest quality version available when you download, and upload to the target platform at its recommended settings without adding any additional compression on your end first.
If you do have the original - if it's your own content and you still have the camera file - always upload from source. Never re-upload a platform-processed version when the original exists. The quality difference is real and permanent.
A Quick Reference - Specs at a Glance
TikTok: 9:16 · 1080×1920 · MP4/MOV · up to 10 min · upload on Wi-Fi
Instagram Reels: 9:16 · 1080×1920 · MP4/MOV · up to 90 sec
Instagram Feed: 4:5 portrait preferred · 1080×1350 · up to 60 min
Instagram Stories: 9:16 · 1080×1920 · 60 sec per card · keep content centred
Facebook: 16:9 or 9:16 · 1080p · MP4/MOV · up to 240 min
X (free): 16:9 or 1:1 · 720p · MP4 · under 140 sec · under 512MB
X (Premium): up to 1080p · up to 3 hrs · up to 8GB
Reddit: 16:9 · 1080p · MP4 · up to 15 min (standard) or 60 min (Premium)
Vimeo: Any ratio · up to 8K · MP4/H.264 recommended · 10–20Mbps bitrate
For platform-specific download guides - if you're pulling content off these platforms rather than uploading to them - see the full breakdowns for TikTok, Instagram, Facebook, X (Twitter), and Vimeo.