What is a hashtag?
A hashtag is a label anyone can create. Put a # in front of a word, or a run of words with no spaces, and most social platforms turn it into a link to every public post using the same tag. The idea started on Twitter in 2007, suggested by a user as a way to group conversations, and spread to Instagram, TikTok, LinkedIn, Facebook, YouTube and Threads, each of which treats tags a little differently.
There are broadly three kinds. Community tags join a conversation that already exists, such as a hobby or a cause. Event and trend tags gather posts around a moment, from an awards show to a news story. Branded tags are owned by a company or a campaign and exist to collect everything posted about it in one place.
Why it matters
Why a hashtag matters
A hashtag makes a post findable by people who do not already follow you. On platforms with tag search and tag pages, a well-chosen tag puts content in front of an audience that is already interested in the subject. For a campaign, a branded hashtag is also a measuring tool: it shows how many people joined in and gathers their posts for the brand to see, share and learn from.
Hashtags also shape how a post reads. A clean, relevant tag looks deliberate; a wall of thirty generic ones looks desperate. The way a brand uses them is part of its tone of voice.
In practice
How a hashtag works in practice
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When a post is published, the platform indexes its hashtags. Anyone who taps the tag or searches for it can see the post among others using it, usually sorted by a mix of relevance and recency. Recommendation systems also read hashtags, along with captions, audio and the video itself, as a clue to what a post is about and who might want it.
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On the brand side, the social team checks a tag before using it: how big it is, what else is posted under it, whether it has been taken over by spam or a different meaning. Branded tags are checked for awkward readings (a tag is all one word, so run-together phrases can spell things nobody intended), then tracked through social listening once the campaign is live.
Watch out
What people get wrong about hashtags
Using them as a substitute for an idea. A branded hashtag does not create a movement; people only use a tag when the thing it stands for is worth joining. The tag is the address, not the invitation.
The other common mistake is stacking dozens of broad tags in the hope of reach. On most platforms today that adds little, and on some it makes content look like spam. A few specific, relevant tags almost always do more than many generic ones.
Brands also forget to check a tag's history. A phrase that seems harmless can already belong to a joke, a protest or a community with no interest in being marketed to, and walking into it uninvited is how hashtags end up in the news for the wrong reasons.
