door hanger

plural door hangers · alternative doorhanger

1. A sign or advertisement that is cut so that it can be hung from the handle or knob of a door.

   1 more example

   The law prohibits you from stuffing your materials into mailboxes, but most communities do not legally frown on doorhangers. These low-priced marketing weapons can do a variety of jobs for you: entice people into your store, tempt them into ordering your product, motivate them to call you for more information, […]

   1990, Jay Conrad Levinson, Guerrilla Marketing Weapons, page 229

2. computingA visual notification that drops down from another element such as a toolbar icon.

   I can basically do whatever I want in Gmail without that hidden doorhanger icon disappearing. Also, if a user simply uses the post-login page as a launching pad for opening links in new tabs or windows, then the doorhanger still remains in its hidden state.

   2010, wmarcello, “Re: Doorhanger behaviour concerns”, in mozilla.dev.apps.firefox (Usenet)