What is the character limit difference between Mastodon and TikTok?

Mastodon allows 500 characters and TikTok allows 2,200.

How do I post to Mastodon and TikTok at the same time?

With PostWire, one API call publishes to both: POST /api/post with platforms set to ["mastodon","tiktok"]. Or one MCP tool call from an AI agent.

Not a direct copy

Cross-posting Mastodon to TikTok: what actually breaks

Not directly. TikTok will not accept a text-only post, so a straight copy is impossible — the post has to be rebuilt for TikTok, not forwarded to it.

Side by side

	Mastodon	TikTok
Characters	500	2,200
Media	optional	a video (required)
Hashtags	2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers	max 5 hashtags, inside the caption (comments are invisible to the algorithm)
Links in body	fine	fine
Needs platform approval	no	yes

What changes, one by one

TikTok will not accept a text-only post

Mastodon posts are frequently text-only. TikTok requires a video on every post, so there is no direct equivalent — you have to attach media before this cross-post is even possible.

You have 1,700 characters you are not using

Mastodon caps at 500 characters, TikTok allows 2,200. Posting the short version verbatim wastes the room TikTok gives you to actually explain the thing.

The hashtag rules are not the same

Mastodon: 2-4 hashtags in CamelCase (#SocialMedia, not #socialmedia) for screen readers. TikTok: max 5 hashtags, inside the caption (comments are invisible to the algorithm). Carrying the tag block across is the single most obvious sign of an automated cross-post.

TikTok needs a title you never wrote

TikTok requires a separate title (max 150 characters). Mastodon has no such field, so there is nothing to copy across — it has to be written.

TikTok needs approval, Mastodon does not

You can post to Mastodon today with a credential you generate yourself. TikTok gates posting behind a platform review — see our API approval notes for what that actually takes.

Why copy-paste cross-posting underperforms

Mastodon is community-first; alt text on media is expected, not optional. TikTok is hook-first, not SEO-first: the first 80-100 characters decide everything. Those are different jobs, so the same words cannot do both well — and every algorithm here demotes text that obviously was not written for it. The fix is not to skip cross-posting; it is to send a native version to each network.

Publish to both in one call

curl -X POST https://postwire.io/api/post \
  -H "Authorization: Bearer $POSTWIRE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "platforms": ["mastodon", "tiktok"],
    "text": "Your post",
    "per_platform": {
      "mastodon": { "text": "The Mastodon version" },
      "tiktok": { "text": "The TikTok version" }
    }
  }'

PostWire's /api/generate writes those per-platform versions for you from a single prompt, respecting every limit in the table above. From an AI agent it is one MCP tool call.

Get an API key free →

Questions people actually ask

Can I cross-post from Mastodon to TikTok?: Not directly. TikTok will not accept a text-only post, so a straight copy is impossible — the post has to be rebuilt for TikTok, not forwarded to it.
What is the character limit difference between Mastodon and TikTok?: Mastodon allows 500 characters and TikTok allows 2,200.
How do I post to Mastodon and TikTok at the same time?: With PostWire, one API call publishes to both: POST /api/post with platforms set to ["mastodon","tiktok"]. Or one MCP tool call from an AI agent.

Other pairs: TikTok to Mastodon · all combinations · which APIs need approval