See ["Flag posts" in the *Help Center*][1].

Flagging **posts** (questions/answers) can be done via:

 - The web site, sometimes aided by tools found here on Stack Apps.
 - The official (i)phone apps.
 - The API.  See [the various `/flags/` routes][2].

<br>
Flagging **chat messages** is included under this tag for now, due to the low volume of flagging related questions here.


  [1]: https://stackapps.com/help/privileges/flag-posts
  [2]: https://api.stackexchange.com/docs