It has flourished in the realm of social media, particularly on Instagram and Twitter where hashtags help to categorise content. Meanwhile, its traditional use with numbers is falling out of fashion.

Hashtags

Start your multi-word tags with a hash, then use camel case

#PlainLanguage

#AnItalianInSydney

Hashtags should:

begin with a hash sign
have no other punctuation
have no spaces between different words
ideally be in camel case.

Without camel case, hashtags are almost indecipherable for assistive software like screen readers.

But try to limit the length of your hashtags as well, and don't rely on them to carry all the content in your post.

#BookLaunch

#soexcitedforthisproductlaunch #beenhardatwork #newdesigneronboard #dontmissout

Numbers

You can use a hash sign in place of the word ‘number’, although this use is now rare

See item #1 on the agenda.

You’re my #1.