How to post one video to every social platform (and what changes on each)

Posting the same video to nine platforms sounds like one job done nine times. In practice it is one job plus a list of small differences, and each one, missed, means a failed upload, a cut-off caption or a Reel that never went out. This guide is that list.

Everything here comes from each platform's official developer documentation as it read on 6 November 2026, linked inline and in the references below. If you are doing this by hand, it tells you what to change before you hit "post". If you are building it into a product, it is the spec.

1. What stays the same

Some things don't need to change:

• The video itself. A 9:16, H.264 MP4 under 90 seconds, with "fast start" (the moov atom at the front of the file), fits the documented limits of every major platform in this guide.
• The core message. What the video is about, and the one thing you want the viewer to do, stays the same everywhere.
• Timing, roughly. Posting everywhere within the same hour or so keeps the conversation in one place.

Everything below is what changes.

2. Shape and length

The full details are in our aspect ratio guide. The parts that most often cause trouble:

• YouTube Shorts: square or vertical, three minutes or less. A 16:9 video is never a Short.
• Facebook Reels: 3 to 90 seconds when published to a Page through the API (Reels publishing). A two-minute Instagram Reel can't go up as a Facebook Reel.
• Instagram Reels: at least 3 seconds, up to 15 minutes and 300 MB (media reference).
• Threads: up to 5 minutes and 1 GB (Threads overview).
• TikTok: each creator has their own maximum length, which the API reports per account, within TikTok's 10-minute API limit.

3. Captions and titles

This is where cross-posting most often goes wrong. Limits differ by a factor of ten or more:

A few things to know:

• YouTube needs a title and the others don't. Write a real one; it is what search and suggestions read.
• YouTube's description limit is in bytes. Emoji and non-Latin scripts use it up two to four times faster than plain English.
• LinkedIn's API needs escaping. Its commentary uses a "little text" format in which reserved characters like ( ) [ ] { } @ # must be escaped, or they are not treated as plain text (little text format).
• Hashtags behave differently. TikTok and Instagram parse them from the caption; a hashtag in a YouTube title or description becomes a link.
• Threads and X are short. Long captions need cutting, or splitting into a thread where the network supports it.

The practical way to handle this is to write one core caption, then fit a version to each network rather than truncating. Reelspan's AI captions do this per platform from the video or your notes, but a person with a checklist works too.

4. Privacy and audience settings

Each network has its own settings, and some have rules about them:

• TikTok requires the creator to choose the privacy level themselves, from the options TikTok returns for that account, with no default. Apps that haven't passed TikTok's audit can only post privately. Our TikTok API guide has the details.
• YouTube has public, unlisted and private, and asks whether the video is made for kids.
• Instagram has no audience setting through the API: posts are public on the account.
• Facebook Reels on a Page: the Reels guide says users should be able to choose the audience, with only "Public" offered for Pages.
• LinkedIn posts are created with a visibility (public for most uses).

5. Scheduling: native vs. your own

Only some APIs let you hand over a video with a "publish at" time:

For everything in the last row, a scheduler has to keep the video and the caption, and call the API at the right moment. That has consequences:

• Instagram containers expire after 24 hours, so create them close to the publishing time, not when the post is scheduled.
• Tokens expire. A post scheduled three weeks out needs a valid token in three weeks. Long-lived Meta user tokens and LinkedIn tokens last about 60 days (Facebook Page tokens taken from a long-lived user token don't expire), and TikTok access tokens about 2 hours, so refresh them on a schedule rather than at posting time.
• Daily limits count at posting time. TikTok allows about 15 posts per creator per day across all apps, Instagram 100 API-published posts per account per 24 hours (an older line in Meta's docs still says 50), and Facebook 30 API-published Reels per Page per 24 hours.

6. AI disclosure labels

If a video contains realistic AI-generated or altered content, most platforms now have an API field for it, and their policies may require you to set it:

Set them consistently. A video labelled on one platform and not on another is an easy mistake to make when each one is set by hand.

7. Check the result on every platform

Uploads don't fail in the same way everywhere. TikTok and Instagram process asynchronously, so a successful API call isn't a published post: you have to poll for the status (or, on TikTok, receive a webhook). YouTube's processing can also fail after the upload completes. Whatever you use, make sure it tells you per platform whether the post went live, and lets you retry the ones that didn't without posting twice to the rest.

Doing it by hand vs. with a tool

For one creator posting once a week, doing this by hand with the checklist above is fine. Past that, the work multiplies: nine platforms, each with its own token, limits, caption rules and failure modes.

That is the job Reelspan does. You upload one video, through the dashboard, the REST API or an AI agent over MCP, and it is reframed for each network, captioned to fit each one, and posted or scheduled, with per-platform results and retries. Some networks still depend on our own platform reviews (see the TikTok and Instagram guides linked above for where those stand). The free plan is enough to try it on your own accounts.