What's shown
The image shows a large face taking up almost the whole frame. The eyebrows are drawn together at the bridge of the nose, the eyes are narrowed and glaring, and the mouth is wide open in a scream, showing clenched teeth. The face is done in rough, uneven lines, typical of early comics made in simple editors.
The main element that makes the image recognizable is the red lettering on the right. The letters "F" and "U" repeat many times, the rows vary in length, and as a result the text looks like a rising scream. This device conveys sound: the reader perceives the lettering almost like a voice breaking into a shriek.
Origin and rage comics
The rage comics genre arose on 4chan's /b/ board in 2008. The first comic, published in August 2008, told the story of water splashing on a user in the bathroom. In the final panel appeared the enlarged face of Rage Guy, screaming a drawn-out "FFFFUUUU." The author of this first comic couldn't be determined, and sources don't say who drew this particular version of the face.
The format was simple: four panels with a short story and the character's final reaction. This template was quickly copied, with new storylines and new characters invented. In September 2008 Trollface appeared, drawn by Carlos Ramirez in Microsoft Paint. Both images quickly became part of the shared visual language of 4chan and Reddit.
Spread
In January 2009 the subreddit FFFFFFFUUUUUUUUUUUU opened on Reddit, soon nicknamed f7u12. Users submitted their own comics there and created new characters, and special generators like Ragemaker and the Memebase Ragebuilder appeared for assembling comics. Thanks to them, the genre became accessible to people who couldn't draw.
The peak of popularity came in late 2011 and 2012. In December 2011 Facebook released rage-comics-style stickers for Messenger, and in February 2012 the series "Rage Comics In Real Life" by PistolShrimps got about 13 million views. In May 2012 The New York Times published a piece on how editing rage comics helps relieve stress.
Typical use
FFFUUU is most often used as a reaction to an annoying event: the internet goes down, something absurd happens in a line, or neighbors are noisy at night. The caption is usually short and describes the cause of the irritation, while the image adds the emotion. In comments it's posted in response to someone's complaint, to show solidarity.
There are also joke variants: the number of letters is changed depending on the strength of the irritation, red text is added to photos, or the comic is reworked for a specific situation. This flexibility helped the meme outlive the era of rage comics and remain among the recognizable reactions.
Why the meme works
The humor rests on exaggeration. The character's reaction is disproportionate to the cause, and that's exactly what triggers laughter: the viewer recognizes their own everyday irritation in the character's rage but sees it taken to an absurd extreme. The scream, rendered in letters, becomes a joke about the emotion itself.
The image is also easy to read even without context. One glance at the face and red letters conveys the emotion, and the repetition of letters creates a rhythm that's easy to remember. That's why FFFUUU remains one of the most recognizable faces of the early internet.