A hashtag is a word or phrase written after the # symbol, with no spaces, such as #LondonFoodie or #SmallBusinessUK. The platform turns it into a clickable label that groups together every public post using the same tag, so people can browse a topic and the platform can understand what a post is about.
How hashtags work
When you add a hashtag to a caption, the platform links it to a page or search result showing other posts with that tag. Hashtags are not case sensitive, so #BristolCoffee and #bristolcoffee land in the same place, but capitalising each word makes them easier to read, including for people using screen readers.
Their role has changed. On Instagram, TikTok and YouTube, the recommendation systems now rely mostly on what is in the video, the words in the caption, on-screen text and audio, and on how people respond. A hashtag is one signal among many rather than the main way content is sorted. Instagram has also cut the number of hashtags a post can carry in recent years, and LinkedIn and Facebook give them little weight. At the time of writing (October 2026) a few relevant tags still help on most platforms, while long blocks of them rarely add anything.
There are broadly three types:
- Topic hashtags, such as #weddingflowers, which describe the subject.
- Community or location hashtags, such as #ShopLocalNorwich, which connect you with a place or group.
- Branded hashtags, unique to your business or a campaign, which collect posts by customers and make user-generated content easy to find.
Why it matters
Used well, hashtags help the right people find a post and help the platform place it in front of them. For a UK local business, an accurate location tag can put your post in front of people browsing their own town. A branded hashtag on a menu, a receipt or an event sign gives customers a simple way to share their experience, and gives you a stream of content and social proof you can reuse with permission.
Hashtags also carry legal weight in one case. When a post is advertising, the UK’s advertising rules expect it to be obviously identifiable as such, and an upfront #ad is the clearest common way to do that on social media. Burying #ad among twenty other tags at the end of a caption does not meet that standard.
Common mistakes
- Pasting the same block of 20 or more tags under every post, whatever the subject.
- Using huge generic tags like #love or #business, where a post disappears in minutes.
- Adding unrelated trending tags to borrow attention, which annoys people and can count as spam.
- Creating a branded hashtag nobody will use because it is long, hard to spell or never promoted offline.
- Not checking what a tag already means, so your brand ends up next to content you would rather avoid.
- Hiding #ad in a cluster of hashtags at the end of a sponsored post.
How to act on it
Choose three to five tags per post that a real person interested in that exact topic might search: one or two about the subject, one about the place if you serve an area, and your branded tag if you use one. Before using any tag, tap it and look at what is already there. If the posts are irrelevant, spammy or off-brand, leave it out.
Put more effort into the words around the hashtags. Clear captions, a descriptive first line, on-screen text and a well-filled profile help with social search more than tags do. If you launch a branded hashtag, keep it short and unique, promote it wherever customers meet you in person, and ask permission before reposting anyone’s photo.
Review results every few months by comparing reach from hashtags with other sources in your platform insights. If they bring almost nothing, cut back. Hashtags are a small part of a wider plan, which is how I treat them in social media strategy work.