How to post one video to TikTok, Instagram Reels and YouTube Shorts at once

When I started making content, I spent about an hour a day on the dumbest possible task: re-uploading the same video to five different apps.

Same file. Same caption, mostly. Five times.

That hour is why Postminion exists. But you don't need Postminion to post one video to TikTok, Instagram Reels and YouTube Shorts. You need a file that all three accept and a caption that works on each. This post covers both, then shows the shortcut.

The manual way

TikTok. Tap the + button, tap Upload, pick your video, add any sound or text, then tap Next. Write your description and hashtags, set who can view it, and tap Post. TikTok's help center walks through each step.

Instagram Reels. Open Create, pick the video, trim it, choose a cover, then write your caption and share. You'll re-type or paste the caption, and probably trim the hashtags (more on that below).

YouTube Shorts. Tap Create, then Upload a video, and pick a vertical or square video. After the editor, YouTube asks for the details: a title of up to 100 characters and your privacy setting. Then you tap Upload.

Three apps, three uploads, three captions. Not hard. Just slow, every single day you post.

One file that works on all three

The good news: the three platforms overlap a lot. One vertical video, 9:16, under 3 minutes, is valid on all of them.

Here are the official limits, checked on September 29, 2026.

Sources: TikTok's help center on video length, TikTok's developer docs on video limits and captions, Instagram's help center on Reel length, Reel size and hashtags, Instagram's publishing API reference, and YouTube's help on 3-minute Shorts and titles and descriptions.

The full rules for each platform are in separate posts on TikTok limits, Reels limits and Shorts limits.

3 minutes is the real ceiling. TikTok and Instagram both accept longer videos, but YouTube only counts a video as a Short if it's square or vertical and up to three minutes. Instagram also says it won't recommend Reels over 3 minutes to people who don't follow you. So if one file has to work everywhere, keep it at 3 minutes or less.

Vertical 9:16 is the safe shape. It's inside Instagram's allowed range, YouTube treats it as a Short, and it fills a phone screen on TikTok.

File size matters if you use a scheduler. Schedulers post through each platform's API, and Instagram's publishing API caps Reels at 300 MB. TikTok's API allows up to 4 GB. So if Instagram is one of your destinations, keep the file under 300 MB.

Postminion's own limit is 3 minutes and 500 MB per video. That lines up with YouTube Shorts, but the 500 MB is above Instagram's 300 MB API cap, so the 300 MB rule above still applies if you post to Reels.

The caption is where the platforms differ

The video can be identical. The caption usually shouldn't be.

Hashtags. Instagram's help center now says you can use up to 5 hashtags on a post. If you paste a TikTok caption with 12 hashtags, trim it. YouTube picks up to three hashtags from your description to show by the title, and ignores every hashtag on a video that has more than 60.

Titles. YouTube needs a title. TikTok and Instagram don't have one. Keep it short, specific, and under 100 characters.

Length. TikTok and Instagram captions both top out at 2,200 characters through their APIs. YouTube splits text into a 100-character title and a description of up to 5,000 characters.

Mentions. An @handle on TikTok may belong to someone else on Instagram. Check tags per platform instead of copying them across.

The practical approach: write one base caption, then make two small edits: cut the hashtags down for Instagram, and write a proper title for YouTube.

Sounds and music don't travel

If you add a trending sound inside TikTok, that sound lives on TikTok. When you upload your own file to Instagram or YouTube, it arrives with whatever audio is baked into it, and each platform checks that audio against its own rights agreements.

Two examples. Instagram says its licensed music library is for personal, non-commercial use, and certain business accounts don't have access to it. YouTube says that from September 24, 2026, new Shorts between one and three minutes with a Content ID claim are no longer automatically blocked, and may stay playable.

The simplest rule for cross-posting: use your own audio (voice, original music, or royalty-free tracks you have rights to), and add platform sounds natively only when a post needs one.

How to do it in one go with Postminion

This is the workflow I built Postminion for.

1. Connect your accounts. TikTok, an Instagram Business or Creator account, and your YouTube channel. Postminion connects through each platform's official login, so it never sees your passwords.
2. Upload the video once. One vertical video, up to 3 minutes and 500 MB (under 300 MB if Instagram is included).
3. Write a default caption. It's used for every account unless you override it.
4. Override where it matters. Give Instagram a caption with fewer hashtags. Add the YouTube title, which Postminion requires (up to 100 characters). Your default caption becomes the YouTube description unless you override that too.
5. Fill in TikTok's settings. TikTok requires a few choices on every post: who can view it, whether comments, Duets and Stitches are allowed, whether it's branded content, and an AI-generated content label if it applies. You also confirm TikTok's Music Usage and Branded Content policy, and pick a cover frame.
6. Schedule it or post now. Pick a date, time and time zone, or publish immediately. Scheduled posts show up on the content calendar.

One upload, three platforms, and the captions are still tuned for each one. If a platform has a temporary hiccup, Postminion retries automatically.

What Postminion can't do here

• No trending sounds or in-app music. Postminion publishes your file as it is. It can't attach TikTok sounds or Instagram's music library. If a post depends on a trending sound, post that one in the app.
• No stickers, polls, collaborator tags or location tags on Instagram.
• YouTube is Shorts only. No long-form videos, and Shorts go out as public.
• Videos over 3 minutes aren't supported. That's usually fine for Shorts, but it rules out longer TikToks and Reels.
• No analytics yet. It's coming soon. Today you can see what was published, not how it performed.

If that list doesn't get in your way, it can give you that hour back. The TikTok, Instagram and YouTube Shorts pages have more detail on each network, and if you've already posted on TikTok and want to move those videos over, read how to cross-post TikTok videos to Instagram Reels.

Try Postminion free for 7 days.

FAQ

Can you post the same video to TikTok, Instagram Reels and YouTube Shorts?

Yes. A vertical 9:16 video of 3 minutes or less is valid on all three. YouTube Shorts are capped at 3 minutes, and Instagram doesn't recommend Reels over 3 minutes to new audiences, so 3 minutes is the practical limit.

What video size works for TikTok, Reels and Shorts?

Use a vertical 9:16 video, up to 3 minutes long. If you post through a scheduler, keep the file under 300 MB, because that's the Reels limit in Instagram's publishing API. Postminion accepts videos up to 3 minutes and 500 MB.

Do YouTube Shorts need a title?

Yes. YouTube asks for a title of up to 100 characters when you upload a Short, and Postminion requires one before it will publish to YouTube. TikTok and Instagram don't use titles, only captions.

How many hashtags can I use on Instagram Reels?

Instagram's help center says you can use up to 5 hashtags on a post. TikTok captions can hold more, so trim your hashtags before reusing a TikTok caption on Instagram.

Can Postminion add trending sounds to my video?

No. Postminion publishes your video file with the audio already in it. It can't add TikTok sounds or Instagram's licensed music, so posts that rely on a trending sound are better published in the app.