Platform Requirements and Limits
Caption lengths, image and video limits and media rules for every social platform CoPost posts to.
Every social platform has its own rules about what a post can contain. Composer checks most of these for you and shows a warning before you schedule. This page collects them in one place.
ℹ️ Platforms change their rules from time to time. These are the limits CoPost currently checks against.
Caption length
| Platform | Maximum characters |
|---|---|
| X (Twitter) | 280 (25,000 for X Premium accounts) |
| 2,200 | |
| TikTok | 2,200 |
| 5,000 | |
| 5,000 | |
| YouTube | 5,000 |
| Threads | 500 |
| Mastodon | 500 |
| 500 | |
| Bluesky | 300 |
| Google Business Profile | 300 |
| 40,000 |
If one platform needs a shorter caption, create a variant for it in Composer. That way the other platforms keep the full text.
Media per platform
| Platform | What you can post | How many | Notes |
|---|---|---|---|
| Facebook (feed) | Images or a video | Up to 10 images | You can't mix images and videos in one post. |
| Facebook Reel | 1 video | 1 | Images are converted to a video automatically. Reels must be 3 to 90 seconds. |
| Facebook Story | 1 image or video | 1 | |
| Instagram (feed) | Images or a video | Up to 10 | Media is required. You can't mix images and videos. |
| Instagram Reel | 1 video | 1 | Images are converted to a video automatically. |
| Instagram Story | 1 image or video | 1 | |
| TikTok video | 1 video | 1 | Images are converted to a short video automatically. Videos can be up to 5 minutes. |
| TikTok photo | Images only | Up to 35 | Images up to 1080p and 20MB each. |
| YouTube | 1 video | 1 | A video is required. Up to 10 minutes and 100MB. |
| Images or a video | Up to 20 images | You can't mix images, videos and GIFs. Videos must be 3 seconds to 30 minutes and up to 200MB. | |
| X (Twitter) | Images, a video or a GIF | Up to 4 images | You can't mix images, videos and GIFs. Images up to 5MB. |
| Threads | Images or a video | Up to 20 images | Images up to 8MB. |
| Bluesky | Images only | Up to 4 | Videos aren't supported yet. Images up to 1MB. |
| Mastodon | Images or a video | Up to 4 images | You can't mix images, videos and GIFs. Images up to 16MB, videos up to 99MB. |
| 1 image or video | 1 | Media is required. | |
| Google Business Profile | Images | Images up to 1MB. | |
| Images or a video | Images up to 20MB, videos up to 1GB. |
If you add more media than a platform allows, CoPost uses the first ones in the order you added them. For example, X gets the first 4 images and the rest are left off.
File size limits for all uploads
| Type | Maximum size |
|---|---|
| Images | 100MB |
| Videos | 512MB |
| GIFs | 15MB |
Some platforms allow less than this; see the table above. Where a platform's image limit is smaller (X, LinkedIn, Bluesky, Threads and Facebook), CoPost tries to resize the image automatically when it publishes.
Other things to know
- Links on X: links in a normal X post are moved out of the caption and posted as the first reply, with a 👇 at the end of the caption.
- Titles: YouTube, Pinterest, Reddit and LinkedIn carousels use the Title field in Composer's Details section. Reddit posts need a title.
- Pinterest boards: each Pin goes to a board. Set a default board for each Pinterest account on the Integrations page, or choose one per post in Composer.
- Polls: X and LinkedIn support polls. LinkedIn polls can only be set in days, not hours or minutes.
- Daily limits: platforms also limit how many posts an account can publish each day. See CoPost Daily Posting Limits.
We are always here to help, so please reach out to [email protected] with any questions!