# What is a hashtag?

Canonical: https://postmesh.app/glossary/hashtag

By PostMesh team. Published 2026-10-31; updated 2026-10-31.

A hashtag is a word or phrase written after the # symbol, like #bakery, that labels a post by topic. On most social networks a hashtag becomes a clickable link to other posts using the same tag, which helps people find your post through search.

## What a hashtag is

A hashtag is a label you add to a post by putting # in front of a word or a run-together phrase: #sourdough, #NYCmarathon, #throwbackthursday. On most networks the tag turns into a link. Tap it and you see other posts with the same hashtag. That's the whole idea: hashtags group posts about the same thing so people can find them.

Merriam-Webster defines a hashtag as a word or phrase preceded by # that classifies or categorizes the text it accompanies, and also uses the word for the # symbol itself. Its note on the word adds that hashtags were designed for categorizing posts on Twitter, now X, but these days often comment on the post too. #notmyfinesthour isn't there to help anyone search; it's a punchline.

The "hash" part is the name of the symbol. Merriam-Webster explains that hash is short for hash mark, another name for the pound sign or octothorpe, and that hash is probably an alteration of hatch, as in the lines artists use for shading.

## Where hashtags come from

Hashtags predate social media. Know Your Meme traces them to IRC chat networks, where channel names start with # followed by a topic. On August 23, 2007, Chris Messina, then a user experience designer at Google, suggested on Twitter using # to group posts. On August 28, 2007, Stowe Boyd called them "hash tags" in a blog post. By October 2007, people were following the San Diego wildfires under #sandiegofire. Merriam-Webster dates the first known use of hashtag to 2007.

The idea spread from there. Know Your Meme notes that Facebook announced support for hashtags in public posts on June 12, 2013. Today X's help center says the feature was created on its platform, and the help centers for Instagram, YouTube and Threads each describe their own version of it.

- Before 2007: IRC chat channels use # in front of a topic name
- Aug 23, 2007: Chris Messina suggests using # to group posts on Twitter
- Aug 28, 2007: Stowe Boyd coins hash tag in a blog post
- Oct 2007: #sandiegofire tracks the San Diego wildfires
- Jun 12, 2013: Facebook adds hashtags to public posts

*Dates from Know Your Meme's Hashtag entry; Merriam-Webster dates the word to 2007.*

## How hashtags work

Put a hashtag in a post on a public account, and the post can show up when someone searches for or taps that tag. X's help center says anyone searching for a hashtag may find your post if your account is public, and that very popular hashtags often become trending topics. Instagram says that if you have a public account and add hashtags, the post becomes visible on the matching search results, and tapping the hashtag shows a page of posts that used it. Forgot to add one? Instagram says you can edit the caption of a post you've already shared or put the hashtag in a comment on it instead.

Privacy changes that. Instagram says posts from private profiles won't appear publicly on hashtag results, so only approved followers see them. And not every tag is searchable: Instagram may make a hashtag unsearchable if its text or the content posted with it keeps breaking its rules, and reviews those tags periodically. Order isn't purely chronological either. Instagram lists when a post was shared, how people engage with it and whether it meets its Recommendation Guidelines among the factors behind what you see first.

## Hashtag rules on each network

| Network | How many | Formatting rules | Where they go |
| --- | --- | --- | --- |
| Instagram | Up to 5 per post, says its help center | Numbers are fine; spaces and special characters like $ or % won't work | Caption or comments; you can only tag your own posts |
| X | As many as you like; X recommends no more than 2 | No spaces or punctuation | Anywhere in a post |
| YouTube | More than 60 and YouTube ignores them all | No spaces; join words, like #TwoWords | Title or description; up to three appear by the title |
| Threads | 1 topic per post | Up to 50 characters; spaces and special characters allowed; # optional | Tagged when you write the post |

- 5: hashtags per Instagram post
- 2: hashtags per post X recommends at most
- 60: hashtags after which YouTube ignores them all
- 1: topic tag per Threads post

*From the Instagram, X, YouTube and Threads help centers.*

> Instagram's limit has changed. Its developer documentation for publishing apps still lists 30 hashtags per caption, but its help center now says you can use up to 5 tags on a post. Go by the app: plan for 5.

Threads works a little differently from the rest. Its help page calls them topics: you tag one per post, it can include spaces, and the # is optional, though Threads notes that including it may help when posts are shared to the fediverse. On YouTube, Google's help page says it picks up to three of the most engaging hashtags from your description to show by your title.

## How to choose good hashtags

**A good hashtag**
- [ ] Describes what's actually in the post
- [ ] Is something people really search for or follow
- [ ] Is specific enough that your post isn't buried
- [ ] Has no spaces or punctuation on networks that don't allow them
- [ ] Uses capital letters at word starts so it's readable, like #SmallBatchBakery
- [ ] Isn't banned, unsearchable or tied to an unrelated trend

Relevance beats volume, especially now that limits are tight. With Instagram allowing 5 and X recommending 2, every tag needs to earn its place. Mix one broad tag with a couple of specific ones, and before you use a tag, tap it to see what's already there; a tag full of unrelated or spammy posts won't help you. Our [hashtag generator](/tools/hashtag-generator) suggests tags from a description of your post, and there are versions tuned for [Instagram](/tools/instagram-hashtag-generator), [TikTok](/tools/tiktok-hashtag-generator) and [LinkedIn](/tools/linkedin-hashtag-generator).

Capitalizing each word, often called camel case, makes a hashtag easier to read and can help screen readers say it as separate words: #SmallBatchBakery instead of #smallbatchbakery. YouTube's own example, #TwoWords, uses the same style. Put hashtags where they don't interrupt the sentence, usually at the end of the [caption](/glossary/caption).

## How people use hashtags

- "Fresh out of the oven #sourdough #SmallBatchBakery"
- "Running my first half this weekend #HalfMarathon"
- "Post your best fall photo with #OurTownInAutumn and we'll share our favorites."
- "Burnt the toast, set off the alarm, woke the baby. #notmyfinesthour"
- "Live updates from the conference all day under #DesignWeek"
- "Tag your entries #ShowYourDesk by Friday."

Some hashtags organize a conversation, like an event or a campaign. Others are jokes or asides that nobody will ever search. A brand running a campaign or a contest might create its own hashtag so entries are easy to find. That works best when the tag is short, unique and checked first to make sure it doesn't already mean something else.

## When not to use hashtags

- Don't add tags that have nothing to do with the post. YouTube calls this misleading and says it can lead to removal; on any network it annoys people.
- Don't over-tag. YouTube ignores every hashtag on a video with more than 60, and Instagram caps posts at 5.
- Don't jump on a trending hashtag about a tragedy or a cause just to sell something.
- Don't use hashtags to harass, mock or expose someone. YouTube lists this as grounds for removal.
- Don't paste the same block of tags under every post whatever it's about.
- Don't rely on hashtags to fix weak content. A clear [reel](/glossary/reel) or post with a good caption does more than any tag.

If your posts seem to have vanished from hashtag pages, check whether your account is private, whether the tag itself has become unsearchable, and whether your account has any restrictions, which is the official side of what people call a [shadowban](/glossary/shadowban).

## Hashtag vs @mention vs keyword

**Hashtag (#)**
- Labels a topic
- Links to other posts with the same tag
- Anyone can use any tag

**Mention (@)**
- Points to a specific account
- Usually notifies that account
- Uses their exact handle

**Plain keyword**
- Ordinary words in the caption
- Can still be found by search
- Reads naturally

A hashtag labels what the post is about. An @mention points at a person or brand by their [handle](/glossary/handle), and on Instagram, the developer documentation says mentioned accounts get a notification when the post goes out. Plain words matter too: X's help center says hashtags help posts show more easily in search, but a clear caption with the right words does a lot of the same work without any # at all.

## Questions

### What does a hashtag do?

It labels a post by topic and, on most networks, turns into a link to other posts using the same tag. On public accounts it helps people find your post through search.

### How many hashtags can you use on Instagram?

Instagram's help center says you can use up to 5 hashtags on a post. Its developer documentation still lists 30, but the app limit is the one to plan for.

### Who invented the hashtag?

Know Your Meme credits Chris Messina with suggesting # for grouping posts on Twitter on August 23, 2007, and Stowe Boyd with coining hash tag five days later.

### Why is it called a hashtag?

Hash is short for hash mark, another name for the # symbol, according to Merriam-Webster. The tag part is because it tags, or labels, a post.

### Do hashtags work on private accounts?

You can add them, but Instagram says posts from private profiles won't appear publicly on hashtag results. Only approved followers see them.

### Can hashtags have spaces?

Not on Instagram, X or YouTube, where a space ends the tag. Threads topics are the exception and can include spaces.

## Related terms

- [Caption](https://postmesh.app/glossary/caption)

- [Handle](https://postmesh.app/glossary/handle)

- [Reel](https://postmesh.app/glossary/reel)

- [Shadowban](https://postmesh.app/glossary/shadowban)

- [Algorithm](https://postmesh.app/glossary/algorithm)

## Sources

- [Merriam-Webster: hashtag](https://www.merriam-webster.com/dictionary/hashtag)

- [Know Your Meme: Hashtag](https://knowyourmeme.com/memes/hashtag)

- [X Help Center: How to use hashtags](https://help.x.com/en/using-x/how-to-use-hashtags)

- [Instagram Help Center: Use hashtags on Instagram](https://help.instagram.com/351460621611097)

- [Instagram Help Center: Why you can't search for certain hashtags on Instagram](https://help.instagram.com/485240378261318)

- [Instagram Help Center: How posts appear on Instagram hashtag search results](https://help.instagram.com/777754038986618)

- [Meta for Developers: IG User Media (caption limits)](https://developers.facebook.com/docs/instagram-platform/instagram-graph-api/reference/ig-user/media)

- [YouTube Help: Find playlists and videos using hashtags](https://support.google.com/youtube/answer/6390658)

- [Instagram Help Center: Tag a topic in your post on Threads](https://help.instagram.com/1356090605000312)