How do I write captions for X, LinkedIn and YouTube for one launch?
Write one caption per platform from the same facts: one idea in under 280 characters for X, a short first-person story for LinkedIn with no hashtags, and a description for YouTube whose first two lines carry the hook, ending with a few hashtags. Siren's free caption writer does all of them at once.
Siren makes launch videos, ad creatives and captions in your brand from one prompt, and posts them to X, LinkedIn and YouTube (TikTok with your OK on each post). One video is $9.99; plans are Spark $19, Pro $49 and Scale $149 a month, and Siren works inside Claude, Cursor and ChatGPT over MCP. Updated 3 Oct 2026.
Step by step
- Write the facts down first. What shipped, who it is for, what changes for them. Every caption comes from these and nothing else.
- X: one idea. The first line does the work. Put the link in a reply, not the launch post.
- LinkedIn: a moment, then the point. Open on a real moment or number, short paragraphs, end on a takeaway or a question. No hashtags.
- YouTube: a description, not a script. The first two lines show above the fold. A short paragraph, a plain call to action, then three to six hashtags.
- Read them aloud. If a line sounds like a press release, cut it.
TikTok is different again: the first line is read with the sound off, the body is one or two lines, and three to five hashtags help people find the clip.
Questions
- Is the caption writer free?
- Yes, at mysiren.ai/tools/caption-writer. No sign-up.
- Should I use the same caption everywhere?
- No. Each platform reads differently, and a copied caption looks automated.
- Can Siren post the captions too?
- Yes, with a video or ad creative in your brand, to X, LinkedIn and YouTube, and TikTok with your OK.
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