Hashtags are the part of a post where the networks disagree most. Instagram refuses a caption with more than 30; TikTok's own app stops at five and its API has no rule at all; YouTube ignores every hashtag on a video once there are more than 60; on Tumblr a hashtag in the text is just text, while one on the last line becomes a tag; on LinkedIn a hashtag is clickable only if it is written in LinkedIn's own markup. This page lists the rules, network by network, from what Preflight enforces and sends when it publishes, checked on 28 October 2026, and ends with how to write one set of tags for several networks.
Hashtag rules by network
| Network | Rule | What happens |
|---|---|---|
| At most 30 hashtags and 20 mentions in a caption | More is refused, because the API refuses it. A first comment can carry the hashtags instead | |
| TikTok | The API has no hashtag rule; the app takes five | Over five is a warning, because extra tags only spend caption characters |
| YouTube | Up to 60 hashtags in the title and description together | Over 60, YouTube ignores every hashtag on the video, so Preflight warns at the count |
| No limit found in LinkedIn Help or the Posts API | Hashtags are rewritten into LinkedIn's template so they stay clickable | |
| Bluesky | Count as the text you type, with the # | Each one is marked as a facet so it is clickable; a tag longer than 64 graphemes or only digits is skipped |
| Threads | One topic tag per post, separate from the text | The tag is stripped of the #, periods and ampersands and cut to 50 characters |
| Tumblr | A last line made only of hashtags becomes the tags | The line leaves the body; hashtags inside the text stay text |
| No hashtag rule enforced | The first comment is the usual place for hashtags or a link | |
| Pinterest, Mastodon, Telegram, Discord | Preflight enforces no hashtag rule | They stay ordinary text |
Instagram: the only hard limit
Thirty is a refusal, not a warning: the 31st hashtag makes the API refuse the whole post, and Preflight stops it in the composer with the count instead. Mentions have their own limit of 20. The same caption can move the hashtags into a first comment, which keeps the caption short and is posted straight after the post. A story is not judged on its caption, because Instagram stories carry none through the API.
TikTok and YouTube: tags that stop helping
TikTok's rule is advice, not enforcement. The Content Posting API has no hashtag limit and the 2,200 characters of the caption are its only one, while the TikTok app itself takes five; past five they earn no reach and only spend characters, so Preflight warns. YouTube's rule is a cliff: with 60 or fewer hashtags they are used, with 61 or more none are. YouTube also has a separate tags field, fitted into 500 characters including commas, and it does not want a leading # there. The #Shorts hashtag helps YouTube's systems and search but does not make a video a Short; the shape and length of the file decide that (see YouTube Shorts limits).
LinkedIn, Bluesky and Threads: clickable only when marked
On these three a hashtag typed as plain text is not necessarily a link. LinkedIn stores a hashtag as a template, {hashtag|\#|coding}, and Preflight rewrites each #tag you type into it, so it stays clickable while the rest of the text is escaped. Hashtags at the end of a long LinkedIn post sit behind the fold and are not seen until someone taps "see more". Bluesky stores text as plain text and turns a hashtag into a link only when the post also carries a facet, a byte range plus the tag; Preflight builds the facet for every hashtag, link and mention. Threads separates the topic: one topic tag is its own field of the first post.
Tumblr: the last line
On Tumblr a hashtag inside a sentence is not linked. Write the tags on the last line, alone, and Preflight removes that line from the body and sends its words as the post's tags. A tags field in the API, comma separated, overrides the last line.
One set of tags for several networks
Write for the strictest network first and see what each adds. A set of up to five hashtags passes Instagram, TikTok and YouTube without a warning; more than five suits Instagram and YouTube but costs TikTok caption space. If the post also goes to Tumblr, put the set on the last line, and if it goes to LinkedIn, expect them to be read only after the fold. The text of each network can be its own: a scheduler with a different caption per network lets Instagram carry 15 hashtags while TikTok carries five and Tumblr turns the last line into tags. The Preflight composer counts the hashtags against each network's rule while you type, and the same check runs from the API and the MCP server. The caption lengths and other rules are compared in TikTok vs Instagram limits, and every network's limits are on the limits page.
Questions people ask
- How many hashtags can you use on Instagram?
- At most 30 in a caption, together with at most 20 mentions. The API refuses a post over either limit, and Preflight stops it in the composer. The hashtags can also go in a first comment.
- How many hashtags should you use on TikTok?
- The TikTok API has no hashtag limit, but the app itself takes five, and hashtags past five earn no reach while using up caption characters. Preflight warns above five.
- Why were all my YouTube hashtags ignored?
- There were more than 60 in the title and description. Past 60, YouTube ignores every hashtag on the video instead of keeping the first ones.
- How do hashtags work on Tumblr?
- Tumblr does not link a hashtag inside the text. If the last line of the post contains only hashtags, Preflight removes the line and uses its words as the post's tags.
- Are hashtags clickable on LinkedIn and Bluesky when scheduled?
- Only if the tool marks them. LinkedIn needs each hashtag in its own template and Bluesky needs a facet for it. Preflight does both, so a hashtag stays a link.