It's kind of like Let's Play, but for videos. The host (usually called a "reactor") watches a video that they've never seen before, and we get to witness their first reactions to it. Some reactors also like doing predictions before they watch the video, or a quick analysis afterwards, but the main part is the reaction itself.
There are several channels on YouTube dedicated mostly to reaction videos (called "reaction channels"). They gather small, but dedicated fandoms, who enjoy watching their favorite reactor's reaction to different videos. Some of these reactors craft a specific persona they play on-camera, to make their reactions more interesting to watch. Their video choice usually involves a movie trailer, music video, viral video, rap battle, or Vine compilation.
Other YouTubers sometimes also make Reaction Videos; "Reacting to my old videos" is an especially popular theme. Another is having a professional (doctor, lawyer, priest...) react to the Artistic Licence with regard to their domain present in many shows.
It has gained traction as a method of avoiding the website's infamous copyright strikes, allowing many of the original removed videos to remain on the site in some form.
Some reaction channels:
- BSL Reaction Asylum
- The Common Man Show: Focuses on the reactions of Indian villagers; mainly Raeen, Sarru and Babu.
- Cr1TiKaL: Even though he voices disdain for the typical reaction content, he has admitted his channel has always been reaction-based even if he does many different kinds of content as well.
- Etika: This individual was well-known for his very hyped-up reactions to Nintendo game announcements.
- FandomReactions: Known for their cheerful, snarky, and Hot-Blooded personalities and analysis of episodes they watched, as well as for their occasional cosplaying. It had two Spin-Off, B And B Videos and AlectricBritSmash.
- Formula 1: Is not primarily a reaction video channel, but does host several in which Formula One drivers and other professionals in the sport react to various kinds of videos about the sport.
- Kyuujin Reacts: Hosted by a female cosplayer duo from Quebec, with in-depth discussion after screenings. Generally tend to react to anime, but have branched into live-action series like Breaking Bad.
- Lost Pause: Noble frequently reacts to compilations of anime-based Vines, "cracks", and memes.
- Half of SMG4 Crew is about Mario and friends reacting to weird stuff online, whether that be spooky memes, TikTok videos, or strange Nintendo commercials.
- The Normies: Hosted by a group of friends who frequently perform skits based on what shows they're reacting to.
- Rarity Dash is a prolific MLP reactor, who started with a reaction to the second installment of the EQUESTRIA GIRLS spin-off series before moving on to reactions to fan works, the show proper, other Western cartoons, and anime.
- React: A series by The Fine Brothers that started back in 2010 and inspired most other YouTube reactors. Their videos feature several people reacting to one video, and then giving their opinions on it. The reactors are grouped together either by their age (kids, teens, adults, elders) or celebrity status (YouTubers, celebrities). This series' popularity was most likely what inspired all other reaction channels on YouTube, even though none of them follow their exact formula.
- Reaction & Review
- Reactistan: A reaction series centered around Pakistani villagers.
- The Reel Rejects: Hosted by Greg Alba (formerly known as Ryan Right), each video features him pairing up with numerous guest stars. They mostly react to movie trailers or videos related to movies. Greg's jokes usually revolve around Self-Deprecation and Camp Straight, and he provides commentary.
- Sesskasays: Reactions and in-depth analysis of episodes she has watched. She hosts an annual event called Doctor Who December, which features her reacting to episodes old and new, as well as showing viewers how to cook and decorate their house with Doctor Who-themed Christmas decor.
- SidemenReacts: The British YouTube group started a channel dedicated to them reacting to YouTube videos in 2020.
- Torchwood Boy: A British reactor with a Campy, pleasant, yet snarky personality who reacts and does in-depth analysis of episodes.
- Trybals: Like the Common Man Show and its parent series, Reactistan, Trybals focuses on the reactions of Indo-Pakistani villagers but has a broader scope of topics.
- Tyrone Magnus: His persona is a boastful Large Ham with ironic undertones of Scary Black Man. He usually reacts to movie trailers, viral videos, or news articles, and provides advice to his viewers.
Examples of this trope in media:
- One episode of The Tonight Show featured Jimmy Fallon having The Roots watch a trailer for Fifty Shades of Grey, with the twist that he edited a Screamer Prank into it.
- Mick Foley shares an anecdote in his second book, Foley is Good, where ABC News showed him a video of some backyard wrestlers and asked for his reaction. Having been tipped off beforehand that they were going to show him some pretty horrific stuff, he said, "That looked like a lot of fun...but I have a feeling there's another video you're going to show me." They showed him the second video, and his response was to say that the kids in the video were being very unsafe and he did not condone any of it. When they broadcast it on TV, they showed the second video but his first reaction, "That looked like a lot of fun!"
- ClickHole parodied this trope in a video where people watch the opening sequence of Up, but instead of being affected by the tragedy depicted in the movie, the viewers make Captain Obvious comments.
- During E3 2019, DK Vine posted a video showing their reaction to Banjo-Kazooie being announced for Super Smash Bros. Ultimate during Nintendo Direct. The video continues further to show their reaction to the follow-up announcement for the then-untitled sequel to The Legend of Zelda: Breath of the Wild... or lack thereof.
- Joel Haver has a video where the plays the role of Lanky Kong, hearing the "DK Rap" for the first time. He's super hyped for the song, until he realizes his verse is nothing but insults—he spends the rest of the video chewing out the other Kongs over the phone.
- The Ultra Fast Pony episode "Ponyville Noire" has an Arson, Murder, and Jaywalking gag where a character's petty crimes are listed: "street robbery, vandalism, react videos..."
- Played for Laughs in JEM REACTS - to the new Jem And The Holograms Trailer. In it, cosplayers roleplay as the Jem characters and react to the trailer of the In Name Only Live-Action Adaptation Jem and the Holograms (2015).
- Scootertrix the Abridged has a side series of Celestia and Luna React videos, where those versions of Celestia and Luna give in-character reactions to My Little Pony toy commercials and fan animations like "Lullaby for a Princess" and "Let It Go (a Nightmare Moon parody)". (The voice actors had seen the videos beforehand and broadly planned most of the jokes, but the actual dialogue was improvised.)
- Family Guy: A cutaway from "Back to the Woods" has Brian showing Stewie the "2 Girls 1 Cup" video and filming his reaction. At first, Stewie is horrified, then decides to search for a "two dudes" version.
- The Simpsons: In "Bart vs. Itchy & Scratchy", Lisa records herself while she watches the premiere of the gender-flipped version of The Itchy & Scratchy Show, while Bart and his friends are boycotting it with a "hate not-watch" party downstairs. While she records, Bart walks in to tell her to turn it down, but he catches a glimpse of the show and laughs at it; his reaction becomes part of the video, and is subsequently branded a hypocrite.
- Steven Universe: In the mini-short "Steven Reacts", Steven reacts to the newest episode of Crying Breakfast Friends, parodying Steven Universe and its viewers.