> ## Documentation Index
> Fetch the complete documentation index at: https://docs.postonce.to/llms.txt
> Use this file to discover all available pages before exploring further.
# Captions for each platform
> Adjust captions per destination in PostOnce: remove comment and DM prompts, rewrite captions with AI, add custom text, remove @mentions, and how line breaks, hashtags and links are handled on each platform.
By default PostOnce copies your caption as it is. You can change it for each destination account under the workflow's **Settings › Destinations**.
1. **Remove comment / DM prompts** removes lines like "Comment GUIDE and I'll DM you the link", which don't work on other platforms.
2. **Rewrite caption with AI** rewrites the caption in the style of the destination platform. Type your own instructions (up to 1,000 characters), or leave the box empty to use the platform's default style. Links, @mentions and disclosure tags like #ad are always kept, and so are blank lines between paragraphs.
3. **Add custom text** adds text before or after every caption, such as "Full video on YouTube". If the caption gets too long for the platform, the original caption is shortened and your text is kept.
Your edits apply in this order: prompts removed, AI rewrite, Instagram mention removal, Threads length, then custom text. If the AI rewrite fails, the original caption is used.
## What the AI rewrite does on each platform
| Platform | Default style |
| - | - |
| TikTok | Short and casual, 1 to 3 lines plus up to 5 hashtags |
| Instagram | The creator's tone in short paragraphs, up to 5 hashtags. Says "link in bio" instead of "click". |
| Facebook | A short first line, links on the last line, up to 3 hashtags |
| LinkedIn | A first line that stands on its own, up to 3 hashtags |
| X | No hashtags, links at the end |
| Threads | Up to 1 hashtag, no hashtag blocks or "link in bio" |
| Bluesky | Up to two sentences, no hashtags |
| Pinterest | No hashtags, and a searchable title if the post has none |
| YouTube | Writes a title when the source has none. Chapter lists are removed on other platforms. |
Hashtags from other platforms like #fyp, #reels and #shorts are removed.
## Other caption settings
* **Remove @mentions from captions** (Instagram): removes the @ from usernames so other accounts aren't tagged.
* **Threads caption length**: 160, 280 or 500 characters. Shortened at a paragraph break or whole word.
* In [Create Post](/help/create-and-schedule-posts), tick **Platform captions** to write a different caption for each account.
## How captions are handled
* **Line breaks** are kept on every platform. On TikTok, PostOnce keeps blank lines between paragraphs, which TikTok normally removes.
* **Too long?** Captions are cut at the platform's limit. See [Platforms at a glance](/help/platform-rules).
* **Hashtags:** Instagram keeps the first 30 and TikTok the first 5.
* **Links:** clickable on Facebook, LinkedIn, X, Threads and Bluesky. Not clickable in Instagram and TikTok captions. On X, only one post per day keeps a clickable link (see [X](/help/platforms/x)).
* **@mentions:** LinkedIn posts them as plain text. Bluesky links them when the handle exists.
## Still stuck?
Search this help center with ⌘ K, or email [support@postonce.to](mailto:support@postonce.to) from the address you use for PostOnce. Include the platform, the approximate time, and the exact message you saw. Never send passwords, access tokens, API keys, or card details.
Something missing from PostOnce? [Request a feature](https://postonce.featurebase.app/) or check the [roadmap](https://postonce.featurebase.app/roadmap).
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