The Internet Movie Database (IMDb), owned by Amazon.com, is an online database of information about movie stars, movies, television shows, commercials, and video games.
The IMDb has an extensive amount of information on works, including basic details such as actors and directors, plot summaries and reviews, as well as more esoteric information such as trivia, continuity errors and other goofs, soundtrack listings, aspect ratios, and alternate versions. Actors, directors, writers and other crew members have their own database entries, listing the movies and programs they worked on, and often also featuring biographies. The expanded database found at akas.imdb.com can be used to find movies from the title under which they were released in many different languages and countries.
The IMDb also reaches beyond being a database for movies and video games, by offering daily movie and TV news, and running special features at various movie events such as the Academy Awards. It has also expanded to provide the sister site IMDbPro, offering additional information to business professionals, such as contact details for people in the movie business, movie event calendars, and more. IMDbPro is not specifically designed for use by the general public, and its content is not free.
Any person with an e-mail account and a web browser that accepts cookies can set up an account with IMDb, then submit information and cast votes to rate various titles. For automated queries, most of the database can be downloaded as (compressed) plain text files and the information can be extracted using the tools provided (typically using a command line interface). 
In 1989 Col Needham and others were participating in the Usenet newsgroup rec.arts.movies, discussing movies and exchanging information. They produced FAQ lists on actors, actresses and directors credits and biographical information on movie makers who had passed away. In late 1990, they had FAQs on almost 10,000 movies and television series. On October 17 1990, Needham posted a collection of UNIX shell scripts which could be used to search the 4 FAQ lists; thus, IMDb was born. At that time however, it was known as the rec.arts.movies movie database.
By 1993, the database had been expanded to include trivia, biographies and plot summaries, and a centralised e-mail interface for querying the database had been created. Later in the year, it moved onto to the World Wide Web (a network in its infancy back then). The database resided on the servers of the computer science department of Cardiff University in Wales. Rob Hartill was the original web interface author. In 1994, the e-mail interface was extended to accept the submission of information, meaning that people no longer had to e-mail the specific list maintainer with their updates. Over the years, the database was run on a network of mirrors across the world with donated bandwidth.
In 1995, it has become obvious to Col Needham and the rest of the volunteers that this project had become too large to continue to maintain on donations and in their spare time. The decision was made to become a commercial venture and in 1996, IMDb was incorporated in the United Kingdom, becoming the Internet Movie Database Ltd. The shareholders were the people maintaining the database and revenue was generated through advertising, licensing and partnerships.
This state of affairs continued until 1998. The database was growing every day, and it was again reaching a critical point; revenues were being spent on equipment, and shareholders were finding it difficult to reconcile the fact that for all their hard work they themselves were getting very little income. Offers had been made by major businesses to purchase the database, however, the shareholders were unwilling to sell if it could not be guaranteed that the information would be accessible to the internet community for free.
It was at this point that Jeff Bezos of Amazon.com appeared. A deal was made, allowing the IMDb to have the ability to pay the shareholders proper salaries for their work, while amazon.com would be able use the IMDb as a resource in their business of selling DVDs and videotapes.
IMDb continues to expand its functionality. In 2002, it added a subscription service known as IMDbPro aimed at entertainment professionals. It provides a variety of services including production and box office details, as well as a company directory. Subscriptions are priced at $12.95 per month, or $99.95 per year (price on 5 April 2005).
One popular feature of the IMDb is the Top 250, a listing of the top 250 feature-length of all-time as voted by the registered users of the website. Only theatrical releases are considered for determination; short subjects, documentaries, miniseries, and made-for-TV movies are ineligible. Users are given the option of rating a movie from "1" (lowest) to "10" (highest). The numbers are then filtered through a mathematical formula (found at the bottom of the list) to produce an overall weighted ranking. To safeguard against "vote stuffing" and other attempts to subjectify the data, the database employs data filters and a vote quota (currently 1250) in an attempt to give a "true Bayesian estimate." Also, only votes from "regular voters" are counted; for reasons of fairness, the criteria for a member account meeting such criteria is a deliberate secret.
The listing is notable for being comprehensive and sometimes startling. Consistently represented on the listing are old movies (e.g., Nosferatu (1922)) and new movies (e.g., Eternal Sunshine of the Spotless Mind (2004)), popular movies (e.g., The Lord of the Rings: The Fellowship of the Ring with more than 150,000 votes) and little seen movies (e.g., Sunrise: A Song of Two Humans with approximately 2,600 votes), and movies from a cross-section of genres (e.g., film noir—Double Indemnity; comedy—Some Like It Hot; romance—Casablanca; fantasy—The Princess Bride; science fiction—Blade Runner; musical—Singin' in the Rain; western—The Good, the Bad and the Ugly; animated—Shrek; anime—Spirited Away; etc.). The listing also carries surprising movies which were not necessarily widely popular hits but which have developed broad followings among more devoted movie fans (e.g., The Shawshank Redemption, Donnie Darko and Memento).
How successful these criteria are in producing an unbiased list is debatable. For instance, newly released movies commonly find their initial ratings artificially inflated by fans who are more likely to see a movie first and develop a love-at-first-sight impression of it, which is contrary to the commonly held belief that a truly great movie should hold up to repeat viewings. It is not unusual, therefore, to find a movie placed among the Top 250 shortly after its release, even as high as the Top 100, only to fall from the list as more people see the movie and fans see the movie repeated times. Another common criticism has been that it is merely a popularity contest and does not therefore reflect any objective knowledge about the history or art of movies. In practice, however, many of the movies atop critical yearly and historical best picture lists appear high on the Top 250 as well (for example: the vast majority of the American Film Institute's "100 Greatest Movies" are also on the IMDB list, many placing very highly; there are four movies in common on the lists' Top Tens), raising the question of whether the opinions of the critics and movie-goers are all that different after all.
The IMDb also has a Bottom 100 feature which is assembled in roughly the same way (there is a 625 vote minimum, rather than 1250).
All volunteers who contribute content to the database retain copyright to their contributions but grant full rights to copy, modify, and sublicense the content to IMDb. IMDb in turn does not allow others to use movie summaries or actor biographies without written permission. Using filtering software to avoid the display of advertisements from the site is also explicitly forbidden. Only small subsets of filmographies are allowed to be quoted, and only on non-commercial websites. The latter restrictions on the use of data may be unenforceable, as the U.S. Supreme Court in Feist v. Rural ruled that collections of facts are not protected by copyright.
The ability of the software to filter content is limited; to a certain extent, staff members gauge the validity of contributed data based on the past reliability of the contributor. Submission policies have been restricted over the years, and approval of new titles to be added has become more cautious, but some listings of unreleased titles and unauthenticated data, particularly in bit roles, persist in the existing database.