Hashtag is a text tag that can be set on task, post or attachment. Those tags can be used to describe object in detail, they can be searched for either in address bar or in Search tab. Every object can be assigned virtually unlimited amount of tags.

You can add hashtag to a task in task properties, in “Hashtags” area, which is opened by clicking # icon, or you can use inline editing to add tags via “Hashtag” column.

To start a quick search on tasks containing a certain hashtag you can leftclick that hashtag with Ctrl button pressed, or you can rightclick on it and select “Search by hashtag” from the menu. This will open Search tab with set criteria and search results.

You can search on several hashtags by Ctrl-leftclicking several hashtags. They will be searched for automatically.

You can add a hashtag while creating or editing a forum post.

Post hashtags are shown at the beginning of text.
By clicking on link you will open a search panel with all project posts that have this hashtag attached.

You can add hashtag to an attachment during creation / editing a forum post containing that attachment.