0 / 2,200 caption units
No issues in these input checks.
A professional (Business or Creator) Instagram account. A personal account cannot publish through any API.Free social media post checker
Check caption length, required titles and media counts for Instagram, LinkedIn, Bluesky and other Mellow Hub destinations. No account, uploads or publishing.
By Mellow · UpdatedCheck your draft before connecting an account
Text and media counts are checked locally using Mellow Hub’s rules. No media is uploaded. Account permissions, actual files, aspect ratio, duration and network-specific delivery checks are outside this preview.
3 destinations selected · 2 input issues found.
0 / 3,000 caption units
- LinkedIn will not publish without text.
Bluesky
0 / 300 caption units
- Bluesky will not publish without text.
Ready to work with your actual channels?
Open Mellow Hub to connect a channel and prepare your post. Your account permissions and media still need checking before publication.
Connect a channel in Mellow Hub (new tab)This checker stays open. Your sample text is not transferred, and opening Hub does not publish anything.
One draft, different requirements
A caption that fits LinkedIn can still be too long for Bluesky. A YouTube upload needs a title; an Instagram post needs media. This tool uses the same input validator as Mellow Hub to surface those differences before you connect a channel or send a post.
Choose the destinations you actually use, paste your caption and describe the media count. Shorten a caption or add a missing title, then compare again. The tool does not fetch files or contact a social network. It is a preview of Hub’s known input rules, not certification that a post will be accepted.
Mellow Hub’s current input limits
| Destination | Caption limit | Media items | Title |
|---|---|---|---|
| 2,200 | 1–10 | — | |
| TikTok | 2,200 | 1–35 | 90 maximum |
| YouTube | 5,000 | 1–1 | 100 maximum · required |
| X | 280 | 0–4 | — |
| 3,000 · required | 0–20 | — | |
| Threads | 500 | 0–20 | — |
| Bluesky | 300 · required | 0–4 | — |
| 500 | 1–1 | 100 maximum | |
| 63,206 | 0–10 | — |
These are Mellow Hub’s enforced limits, generated from its platform registry. They can be more conservative than a platform’s native editor or a particular paid account tier. Placement and media type can narrow the allowed counts. TikTok Business uses a separate connection mode with the same caption and media-count limits shown here.
Why an emoji can change the count
The counter follows Hub’s implementation: Bluesky uses grapheme clusters when the browser supports them, while other destinations use UTF-16 code units. A joined emoji can therefore produce different totals. X also applies its own weighted rules for text and links; this preview does not reproduce that network’s final counter. Check the native preview when a caption is close to a limit.
What to do with a draft that does not fit
- Keep the main idea and write a shorter version for the destination that needs it.
- Use a format that fits the selected surface. A Reel and a carousel need different media.
- In Hub, use
perChannelto override one channel’s caption instead of shortening every version. - Run the authenticated validation step against your actual connected channels, then review the final post and its authority.
The MCP publishing guide explains the agent workflow. The REST scheduling guide shows the request and retry sequence. Both lead to the full reference.
Does passing these checks mean a post is live?
No. It means this set of input checks found no issue. A connected account, provider enablement, valid media and the right permissions are still required. After publishing, inspect each channel’s result and public URL. One accepted request can still produce a partial result across destinations.
Are captions saved?
The checker keeps your text in this page’s memory. It does not send the caption to Mellow, a model provider or a social network. Refreshing clears it. Normal site visit analytics may still apply.