F

In Twitch chat, viewers most often spam F when a stream has accidentally disconnected. This practice began in 2014, after the game Call of Duty: Advanced Warfare included a funeral scene that prompted players to press F to pay their respects to a dead NPC.

Now, online forum and Twitch users often spam F to "pay their respects" to actual deceased people as well as those who have "died" of embarrassment. On Twitch specifically, users also spam F when a streamer's stream accidentally goes dead, in order to pay respect to the "fallen" streamer.

In personal ads and forum posts that require a poster to specify their gender, F is short for "female." Usually, a poster's gender is accompanied by their age. For example, a 26 year-old female may write her age and gender as 26F.

In much the same way, M stands for "male" in personal ads and forum posts, and NB stands for "non-binary." People may also use these abbreviations to specify their gender when answering the question "Are you male, female, or other?"