Hashtag

When you type # followed by letters or numbers, the platform detects it and links it to a tag page listing other posts with the same tag. A space ends the hashtag, so multi-word tags are written as one word — #lostandfound — often with capitals (#LostAndFound) to keep them readable. Tapping the tag takes you to everything else posted under it, which makes hashtags one of the simplest tools for social discovery: finding people and posts beyond the accounts you already follow.

• #bookrecs — an ongoing topic people browse whenever they want something to read.
• #examweek — a timely tag that is busy for a few days, then quiet.
• #puneeats — a local tag that connects people in the same city.

The convention started with users rather than companies: Chris Messina proposed using # to group posts on Twitter in 2007, and platforms later built it into their products.

• Be specific. #pottery reaches people who care about pottery; #art reaches everyone and no one.
• A few well-chosen tags beat a wall of them, which reads as spam.
• Check the tag page first to see whether people already use it the way you mean.
• Don't attach a trending tag to an unrelated post — readers notice, and it can break platform rules.

Hashtags matter most where people browse by topic. On a feed that is heavily ranked, a tag is only one of many signals, and the right audience may find your post anyway. On a tag page sorted newest first, the tag is the whole point: it is how someone searching for #bookrecs tonight finds the review you posted an hour ago.