In a nutshell
A hashtag is a label that sorts posts by topic. When you put # before a word, as in "#SpringMenu," the word becomes clickable, and people who press it see the posts with the same hashtag. Spaces and symbols cut it off partway, so write it as one continuous word.
Differences by network
| Network | How it works | Guideline for number |
|---|---|---|
| X | A label that classifies a post | Official Help recommends up to 2 |
| Added to captions and comments | Up to 5 per post in the official Help | |
| Threads | One "topic" per post | 1 |
X's Help says you can use as many hashtags as you like, but recommends using no more than 2 in a single post (How to use hashtags). On Instagram, the Help says up to 5 hashtags can be added to one post (Instagram hashtags). Rules on numbers can change, so please read this as of October 2026.
What business accounts should watch for
More hashtags do not mean more reach. In the recommendation system X has published, hashtags are not counted as a score. Adding more makes a post harder to read and more likely to look like a hard sell. For a business account, it suits better to narrow down to the one tag that represents the post's topic.
When you create your own hashtag for a campaign, first search to check it isn't already used with another meaning. More on using them is in How to use hashtags.
If you do add them, choose ones that fit the post's content and that people actually search with. Lining up unrelated hashtags can become a reason a post is less likely to be recommended (shadowban). The overall use is explained in How to use hashtags.
In SNS TOWN
In the pre-post check, posts with two or more hashtags are stopped when AI drafts or the post cycle send them to X. For posts you write yourself and for networks other than X, only a caution is shown. AI drafts are also instructed to write with 0 to 1 hashtags from the start. For Threads, the composer has a topic field that takes up to 50 characters.
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