Therefore, the hashtag "was created organically by Twitter users as a way to categorize messages." Today they are for anyone, either with or without technical knowledge, to easily impose enough annotation to be useful without needing a more formal system or adhering to many technical details.
Internationally, the hashtag became a practice of writing style for Twitter posts during the 2009–2010 Iranian election protests; Twitter users inside and outside Iran used both English- and Persian-language hashtags in communications during the events.
In many cases other characters are also allowed, in particular accented characters used in many languages, but handling may vary from one client to another, and from time to time as standards evolve.
The use of embedded capitals (Camel Case) increases readability and avoids confusion; a (real) pen shop would be advised to use #Pen Island rather than all lower-case.Twitter has an algorithm to tackle attempts to spam the trending list and ensure that hashtags trend naturally.Although the hashtag started out most popularly on Twitter as the main social media platform for this use, the use has extended to other social media sites including Instagram, Facebook, Flickr, Tumblr, and Google .In order for topics to trend, there has to be a consensus, whether silent or stated, that the hashtag refers to that specific topic.Hashtags also function as beacons in order for users to find and "follow" (subscribe) or "list" (organize into public contact lists) other users of similar interest.