Life in a Day is a crowd-sourced documentary film comprising an arranged series of video clips selected from 80,000 clips submitted to the YouTube video sharing website, the clips showing respective occurrences from around the world on a single day, 24 July 2010.

The film is 94 minutes 53 seconds long and includes scenes selected from 4,500 hours of footage in 80,000 submissions from 192 nations. The completed film debuted at the Sundance Film Festival on 27 January 2011 and the premiere was streamed live on YouTube. On 31 October 2011, YouTube announced that Life in a Day would be available for viewing on its website free of charge, and on DVD., YouTube's official blog ().Barrett, Brian, Life in a Day: Watch the Beautiful YouTube-Fueled Epic Right Now (archive), Gizmodo, 31 October 2011.

Production The film was produced by Scott Free Productions and the YouTube video sharing site. The film was distributed by National Geographic Entertainment. The visual effects were designed by Lip Sync Post.

The film was the creation of a collaboration with YouTube, Ridley Scott Associates and LG electronics, announced on 6 July 2010. Users sent in videos supposed to be recorded on 24 July 2010, and then Ridley Scott produced the film and edited the videos into a film with Kevin Macdonald and film editor Joe Walker, consisting of footage from some of the contributors. All chosen footage authors are credited as co-directors. Users retained the copyrights to their video submissions but agreed to grant a non-exclusive license for their footage to be used in the film.

The film's music was composed by composer and conductor Harry Gregson-Williams, along with Matthew Herbert. The film's opening song, composed by Herbert, was performed by English singer-songwriter Ellie Goulding. The film also features the song "Jerusalem" by Kieran Leonard and "Future Prospect" by Biggi Hilmars.

Macdonald told The Wall Street Journal that the project was initially conceived as a way to commemorate the fifth birthday of YouTube, and that he wanted to "take the humble YouTube video, ... and elevate it into art."Dodes, Rachel, "‘Life in a Day' Director Aims to Elevate YouTube Videos Into Art" (archive), edited interview transcript in The Wall Street Journal "SpeakEasy" section, 22 July 2011. Editor Joe Walker said that as he understood it, the concept for the crowd-sourced documentary came from Ridley Scott's production company "Scott Free U.K." and from YouTube, while Macdonald explained more specifically that "the inspiration for me was a British group from the 1930s called the Mass Observation movement. They asked hundreds of people all over Britain to write diaries recording the details of their lives on one day a month and answer a few simple questions. ... These diaries were then organised into books and articles with the intention of giving voice to people who weren't part of the "elite" and to show the intricacy and strangeness of the seemingly mundane."Watercutter, Angela, "Life in a Day Distills 4,500 Hours of Intimate Video Into Urgent Documentary" (archive), Wired magazine, 29 July 2011.

Macdonald began his "Around the world in 80,000 clips" article in The Guardian by posing the questions, "What do you love? What do you fear? What's in your pocket?" and explaining that "one day last summer, I asked ordinary people around the world to answer those three questions and spend a day filming their lives."Macdonald, Kevin, "Life in a Day: Around the world in 80,000 clips" (archive), The Guardian, 7 June 2011. The 80,000 individual clips received amounted to 4,500 hours of electronic footage. Macdonald explained that about 75% of the film's content came from people contacted through YouTube, traditional advertising, TV shows, and newspapers; the remaining 25% came from cameras sent out to the developing world, Macdonald pointing out "It was important to represent the whole world." At a reported cost of £40,000, "we did resort to snail mail for sending out 400 cameras to parts of the developing world – and getting back the resulting video cards." Macdonald later remarked that he regretted not sending out a far smaller number of cameras but providing training in camera operation and desired type of content: "Naively, I hadn't realised how alien, not only the concept of a documentary is to a lot of people (in the developing world), but also the idea that your own opinions are worth sharing."

Macdonald expressed to The Wall Street Journal that the film "could only be made in the last five years because ... you can get enough people who will have an understanding of how to shoot something." Walker told Wired magazine's Angela Watercutter that the film "couldn't have been made without technology. Ten years ago it would've been impossible." Macdonald explained that YouTube "allowed us to tap into a pre-existing community of people around the world and to have a means of distributing information about the film and then receiving people's 'dailies'. It just wouldn't have been organizationally or financially feasible to undertake this kind of project pre-YouTube."

The filmmaking team "used YouTube's ability to collect all of this material and then we had this sort of sweatshop of people, all multilingual film students, to sift through this material. It couldn't have been done any other way. Nobody had ever done a film like this before, so we had to sort of make it up as we went along." "To put (the 4500 hours of raw footage) in context, I just cut a feature film for Steve McQueen and there's 21 hours of [film] for that."

Walker, whose team edited the whole film over seven weeks, remarked to Adam Sternbergh of The New York Times that "The analogy is like being told to make Salisbury Cathedral, and then being introduced to a field full of rubble. You have to start looking for buttresses and things that connect together."Sternbergh, Adam, "Around the World in One Day" (archive), The New York Times, 22 July 2011. Walker indicated that a team of roughly two dozen researchers, chosen both for a cinematic eye and proficiency with languages, watched, logged, tagged, and rated each clip on a scale of one to five stars. Walker remarked that "the vast amount of material was two stars", and that he and director Kevin Macdonald reviewed the four-star and five-star rated clips.

In addition to the star rating system, the editing/selecting team also organised the 80,000 clips according to countries, themes and video quality as part of the selection process, and further had to convert from 60 different frame rates to make the result cinematically acceptable. All the logging and researching was done using the Quantum CatDV media asset management software.

Themes and content Macdonald said that the film focused on a single day "because a day is the basic temporal building block of human life—wherever you are," with Walker adding that the particular day, 24 July 2010, was chosen because it was the first Saturday after the World Cup.

Concerning the chronology of the film and the order of the clips, Macdonald explained that he let the 300 hours of "best bits" tell him what the themes and structure of the film should be, likening the material to a Rorschach test—"you will see in it what you want to see in it." Joe Walker further explained that "We always wanted to have a number of structures, so it's not just midnight to midnight, but it's also from light to dark and from birth to death. ... bashing things together and making them resonate against each other and provoking thought."

Macdonald said he saw the movie "as a metaphor of the experience of being on the Internet. ... clicking from one place to another, in this almost random way…following our own thoughts, following narrative and thematic paths." Betsy Sharkey wrote in the Los Angeles Times that "this fast-paced documentary is shaped as much by Internet savvy as traditional filmmaking, which doesn't make the experience of it any less satisfying, or the implications any less provocative."Sharkey, Betsy, "Movie review: 'Life in a Day'" (archive), the Los Angeles Times, 29 July 2011. (Sharkey slightly misstates the "love/fear/pockets" quotation.) "The story is told through the voices of the contributors, but mostly it's the images that do the heavy lifting."

Macdonald explained that the film "doesn't have a traditional story or a traditional narrative, but it has thematic movement [and] recurring characters." He praised certain specific contributions, including "the most technically amazing skydiving shot I have ever seen in any film" and "a hand going up to a window pane and picking a fly off and filming the hand walking through the house and letting the fly go—and you see the fly take off in the distance." Asked if there any particular submission that crystallized the film's theme, Macdonald cited "the family who had been going through cancer." More generally, Macdonald praised the immediacy that a handycam permits.

Ian Buckwalter of Washingtonian magazine said that "the familiar beats of the day (were) cut together to show that we're actually far more similar than we are different."Buckwalter, Ian, “Another Earth,” “Life in a Day,” and “Cowboys & Aliens”: Movie Tickets (archive), "Arts and Events" section of Washingtonian magazine online, posted 27 July 2011. The Washington Post Michael O'Sullivan similarly noted that "the people whose lives form the spine of Life feel familiar... Their hopes and joys, disappointments and fears are our own."O'Sullivan, Michael, "Life in a Day" (Critic's Pick) (archive), The Washington Post, 29 July 2011. Liz Braun, writing in the Toronto Sun, said that "The overall sense of the project appears to be: It's good to be alive. ... According to the film, there are things that divide us as humans, but far more things that unite us."Braun, Liz, (QMI Agency), "'Life in a Day' a free-wheeling look at human events" (), Toronto Sun, 29 July 2011. Toronto Star critic Peter Howell was in accord, observing that the "film shows things (what) billions of us do every day, perhaps thinking that we are somehow alone in our pursuits. Yet we couldn't be more connected."Howell, Peter, "Life in a Day: A brief, shining moment on Planet Earth" (archive), The Toronto Star, 28 July 2011. However, The Boston Globe's Tom Russo gave director "Macdonald and crew credit for picking out good, clear, telling contrasts, and not sweating potential heavy-handedness," citing contrasts between "one smug contributor pull[ing] a set of Lamborghini keys from his pocket, ... then mov[ing] on to ragged-looking Third Worlders amusedly scoffing at the idea that they'd have anything in their pockets," and a Westerner "quietly worries about losing his hair, while an older Afghan man quietly worries about getting through the day alive."Russo, Tom, "Life in a Day: From trivial to beautiful in ‘Life'" (archive), The Boston Globe, 5 August 2011.

Sharkey described the progression of the film: "Beginning with videos that start pre-dawn then moving through morning, afternoon and evening, ... the rituals that define a day begin to emerge. Beyond an extraordinary range of cultures, terrain and styles reflected, which are captivating on their own, the film stands as a stirring reminder of how ordinary and yet eclectic humanity can be. If Life in a Day is any measure, we are a quirky, likeable, unpredictable and yet predictable bunch."