IMDb (an acronym for Internet Movie Database) is an online database of information related to films, television series, podcasts, home videos, video games, and streaming content online – including cast, production crew and personal biographies, plot summaries, trivia, ratings, and fan and critical reviews. IMDb began as a fan-operated movie database on the Usenet group "rec.arts.movies" in 1990, and moved to the Web in 1993. Since 1998, it has been owned and operated by IMDb.com, Inc., a subsidiary of Amazon.
The site's message boards were disabled in February 2017. As of 2019, IMDb was the 52nd most visited website on the Internet, as ranked by Alexa. the database contained some million titles (including television episodes), million person records, and 83 million registered users.
Features
The title and talent pages of IMDb are accessible to all users, but only registered and logged-in users can submit new material and suggest edits to existing entries. Most of the site's data has been provided by these volunteers. Registered users with a proven track record are able to add and make corrections to cast lists, credits, and some other data points. However, the addition and removal of images, and alterations to titles, cast and crew names, character names, and plot summaries are subject to an approval process; this usually takes between 24 and 72 hours.
On October 2, 2007, character filmographies were added. Character entries are created from character listings in the main filmography database, and as such do not need any additional verification by IMDb staff. They have already been verified when they are added to the main filmography.
Registered users can choose their username, and most are pseudonymous. There is no single index of contributors, no index on each profile page of the items contributed, and—except for plot synopses and biographies—no identification of contributors to each product's or person's data pages. Users are also invited to rate titles on a scale of 1 to 10, and the totals are converted into a weighted mean-rating, with filters in place to mitigate ballot-stuffing.
User profile pages show a user's registration date and, optionally, their personal ratings of titles. Since 2015, "badges" can be added showing a count of contributions. These badges range from total contributions made to independent categories such as photos, trivia, and biographies. If a registered user or visitor is in the entertainment industry and has an IMDb page, they can add photos through IMDbPRO.
User ratings of films
As one adjunct to data, the IMDb offers a rating scale that allows users to rate titles on a scale of one to ten.
IMDb indicates that submitted ratings are filtered and weighted in various ways to produce a weighted mean that is displayed for each title. It states that filters are used to deter ballot stuffing; the methodology and details for how its ratings are calculated are confidential and not accessible to the public. In fact, it sometimes produces an extreme difference between the weighted average and the arithmetic mean.
Rankings
The IMDb Top 250 is a list of the top rated 250 films, based on ratings by the registered users of the website using the methods described. , The Shawshank Redemption, directed by Frank Darabont, is No. 1 on the list, and has been since 2008. The "Top 250" rating is based on only the ratings of "regular voters". The number of votes a registered user would have to make to be considered as a user who votes regularly has been kept secret. IMDb has stated that to maintain the effectiveness of the Top 250 list they "deliberately do not disclose the criteria used for a person to be counted as a regular voter". In addition to other weightings, the Top 250 films are also based on a weighted rating formula referred to in actuarial science as a credibility formula. This label arises because a statistic is taken to be more credible the greater the number of individual pieces of information; in this case from eligible users who submit ratings. Although the current formula is not disclosed, IMDb originally used the following formula to calculate their weighted rating:
where: is the weighted rating; is the mean rating for the movie, from 1 to 10; is the number of votes for the movie; is the minimum votes required to be listed in the Top 250 (currently 25,000); and is the mean vote across the whole report (currently 7.0).
The variable in this formula is equivalent to a Bayesian posterior mean (see Bayesian statistics).
The IMDb also has a Bottom 100 feature which is assembled through a similar process although only 10,000 votes must be received to qualify for the list.