Cross-post a video
One video to YouTube, TikTok, Reels
Short-form video is a three-platform game: YouTube Shorts, TikTok, Instagram Reels. The video you upload is almost always the same; the copy, hashtags, and title absolutely aren’t. Here’s how OpenPost lets you ship one video to all three in one composer pass.
The video you’ll want
Aspect
9:16 vertical
Length
15–60 seconds hits everywhere
Codec
H.264 MP4, AAC audio
Resolution
1080 × 1920 minimum
File size
Under 250 MB ideal; we transcode if needed
Set up the post
Open a new post, attach the video
Drag into the composer. You’ll see three preview windows on the right — YouTube, TikTok, Instagram. Each shows the video with that platform’s UI chrome overlaid.
Tick all three channels
YouTube Shorts, TikTok, Instagram Reels. If you haven’t connected one of them, OpenPost links straight to the OAuth flow.
Write the base caption
This is the fallback for any channel you don’t override. Keep it short — TikTok’s cap is 2,200 but only the first ~90 chars show above the fold.
Override per channel
Click into each preview to override its copy.
- YouTube Shorts — Title (under 100 chars) + description. Hashtags boost discovery.
- TikTok — Caption under 150 chars performs best. Mix 3–5 niche + trending hashtags.
- Instagram Reels — Longer caption is fine. First line is the hook that shows in the grid.
Pick cover frames (optional)
Each channel lets you select a custom thumbnail. Click the preview’s Coverbutton and scrub to the frame you want. If you skip, we use the video’s first sharp frame.
Schedule
Same scheduler as any post. Consider posting to all three at the same time to maximize same-day views, or stagger by an hour to spread the analytics spike.
What OpenPost does behind the scenes
- Transcodes to each platform’s preferred codec profile (Instagram is fussy about H.264 high profile; TikTok accepts most anything).
- Adds platform-required padding for YouTube Shorts (must be under 60 seconds, 9:16 only).
- Extracts an optimal poster frame using motion detection — we pick a sharp frame roughly 2 seconds in.
- Strips location EXIF and private metadata before upload.
Common pitfalls
- Music copyright— Reels and TikTok each run their own content-ID. A track that’s safe on one can be blocked on the other. Test with an unlisted upload if you’re unsure.
- Branded content tags— Instagram Reels and TikTok both require tagging sponsored videos. Toggle the Branded content switch in the per-channel composer; it sets the right flags via each API.
- YouTube Shorts > 60s— becomes a regular YouTube video, not a Short. OpenPost will warn and offer to trim before publishing.
- Captions/subtitles— burn them into the video (via your editor) if you want them on all three. Native caption APIs are inconsistent across platforms.