The Internet Movie Database (abbreviated IMDb ) is an online database of information related to films, television programs and video games, including cast, production crew, fictional characters, biographies, plot summaries, trivia and reviews, operated by IMDb.com, Inc., a subsidiary of Amazon. As of December 2017, IMDb has approximately 4.7 million titles (including episodes), 8.3 million personalities in its database,  as well as 83 million registered users.
The site enables registered users to submit new material and edits to existing entries. Although most data is checked, especially when being submitted by new users before going live, the system has been open to errors, and some sections are even abused. Users with a proven track record of submitting factual data are given instant approval for minor additions such as filming locations, however, Image, name, character name, plot summaries, and title changes are screened before publication, and usually take between 24-72 hours to appear. Users are also invited to rate any film on a scale of 1 to 10, and the totals are converted into a weighted mean -rating that is displayed beside each title, with online filters employed to deter ballot-stuffing.
Anyone with an internet connection can view the movie and talent pages of IMDb. A registration process is necessary however, to contribute info to the site. A registered user chooses a site name for themselves, and is given a profile page. This profile page also shows how long a registered user has been a member, as well as personal movie ratings (should the user decide to display them), and is also awarded badges representing how many contributions any particular registered user has submitted. These badges range from total contributions made, to independent categories such as photos, trivia, bios, etc. If a registered user or visitor happens to be in the entertainment industry, and has an IMDb page , that user/visitor can add photos to that page by enrolling in IMDbPRO. 
History before website
IMDb originated with a Usenet posting by British film fan and computer programmer Col Needham entitled "Those Eyes", about actresses with beautiful eyes. Others with similar interests soon responded with additions or different lists of their own. Needham subsequently started an "Actors List", while Dave Knight began a " Directors List", and Andy Krieg took over "THE LIST" from Hank Driskill, which would later be renamed the "Actress List". Both lists had been restricted to people who were alive and working, but soon retired people were added, so Needham started what was then (but did not remain) a separate "Dead Actors/Actresses List". The goal of the participants now was to make the lists as inclusive as possible.
By late 1990, the lists included almost 10,000 movies and television series correlated with actors and actresses appearing therein. On October 17, 1990, Needham developed and posted a collection of Unix shell scripts which could be used to search the four lists, and thus the database that would become the IMDb was born.  At the time, it was known as the "rec.arts.movies movie database".
On the web
The database had been expanded to include additional categories of filmmakers and other demographic material as well as trivia, biographies, and plot summaries. The movie ratings had been properly integrated with the list data, and a centralized email interface for querying the database had been created by Alan Jay. Later, in 1993, it moved onto the World Wide Web, (a network in its infancy at that time) under the name of Cardiff Internet Movie Database .  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 email interface was revised to accept the submission of all information, which enabled people to email the specific list maintainer with their updates. However, the structure remained so, that information received on a single film was divided among multiple section managers, the sections being defined and determined by categories of film personnel and the individual filmographies contained therein. Over the next few years, the database was run on a network of mirrors across the world with donated bandwidth. 
As an independent company
In 1996 IMDb was incorporated in the United Kingdom, becoming the Internet Movie Database Ltd. Founder Col Needham became the primary owner as well as the figurehead. General revenue for site operations was generated through advertising, licensing and partnerships.
As Amazon.com subsidiary (1998–present)
In 1998, Jeff Bezos, founder, owner and CEO of Amazon.com, struck a deal with Needham and other principal shareholders to buy IMDb outright for approximately $55 million  and attach it to Amazon as a subsidiary, private company.  This gave IMDb the ability to pay the shareholders salaries for their work, while Amazon.com would be able to use IMDb as an advertising resource for selling DVDs and videotapes.
IMDb continued to expand its functionality. On January 15, 2002, it added a subscription service known as IMDbPro, aimed at entertainment professionals. IMDbPro was announced and launched at the 2002 Sundance Film Festival. It provides a variety of services including film production and box office details, as well as a company directory and the ability of subscribers to add personal information pages with details at variance with pages about them appearing in the database.
As an additional incentive for users, as of 2003, users identified as one of "the top 100 contributors" of hard data received complimentary free access to IMDbPro for the following calendar year; for 2006 this was increased to the top 150 contributors, and for 2010 to the top 250.  In 2008 IMDb launched their first official foreign language version with the German IMDb.de. Also in 2008, IMDb acquired two other companies, Withoutabox and Box Office Mojo.
The website was originally Perl -based, but IMDb no longer discloses what software it uses for reasons of security.  As of May 2011, the site has been filtered in China for more than one year, although many users address it through proxy server or by VPN.  On October 17, 2010, IMDb launched original video (www.imdb.com/20) in celebration of its 20th anniversary. 
Actors, crew, and industry executives can post their own resume and upload photos of themselves for a yearly fee. This fee gives them membership in IMDbPro. IMDbPro can be accessed by anyone willing to pay the fee, which is $19.99 USD per month, or if paid annually, $149.99. Membership enables a user to access the rank order of each industry personality, as well as agent contact information for any actor, producer, director etc. that has an IMDb page. Enrolling in IMDbPro for industry personnel, enables those members the ability to upload a head shot to open their page, as well as the ability to upload hundreds of photos to accompany their page. Anyone can register as an IMDb user and contribute to the site as well as view its content, however those users enrolled in IMDbPro have greater access and privileges. 
On January 26, 2006, "Full Episode Support" came online, allowing the database to support separate cast and crew listings for each episode of every television series. This increased the number of titles in the database from 485,000 to nearly 755,000.
On October 2, 2007, the characters' filmography was 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.
On September 15, 2008, a feature was added that enables instant viewing of over 6,000 movies and television shows from CBS, Sony and a number of independent film makers, with direct links from their profiles.  Due to licensing restrictions, this feature is available only to viewers in the United States.
Content and format
Data provided by subjects
In 2006, IMDb introduced its "Résumé Subscription Service", where actors and crew can post their own résumé and upload photos of themselves  for a yearly fee.  The base annual charge for including a photo with an account was $39.95 until 2010, when it was increased to $54.95. IMDb résumé pages are kept on a sub-page of the regular entry about that person, with a regular entry automatically created for each résumé subscriber who does not already have one. 
As of 2012, Resume Services is now included as part of an IMDbPro subscription, and is no longer offered as a separate subscription service.
Copyright, vandalism and error issues
All volunteers who contribute content to the database technically retain copyright on their contributions but the compilation of the content becomes the exclusive property of IMDb with the full right to copy, modify, and sublicense it and they are verified before posting.  Credit is not given on specific title or filmography pages to the contributor(s) who have provided information. Conversely, a credited text entry, such as a plot summary, may be corrected for content, grammar, sentence structure, perceived omission or error, by other contributors without having to add their names as co-authors. Due to the time required for processing submitted data or text before it is displayed, IMDb is different from user-contributed projects like Wikipedia, Discogs or OpenStreetMap in that contributors cannot add, delete, or modify the data or text on impulse, and the manipulation of data is controlled by IMDb technology and salaried staff. 
IMDb has been subject to deliberate additions of false information; in 2012 a spokesperson said: "We make it easy for users and professionals to update much of our content, which is why we have an 'edit page.' The data that is submitted goes through a series of consistency checks before it goes live. Given the sheer volume of the information, occasional mistakes are inevitable, and, when reported, they are promptly fixed. We always welcome corrections." 
The Java Movie Database (JMDB)  is reportedly creating an IMDb_Error.log file that lists all the errors found while processing the IMDb plain text files. A Wiki alternative to IMDb is Open Media Database  whose content is also contributed by users but licensed under CC-by and the GFDL. Since 2007, IMDb has been experimenting with wiki-programmed sections for complete film synopses, parental guides, and FAQs about titles as determined by (and answered by) individual contributors.
Data format and access
IMDb does not provide an API for automated queries. However, most of the data can be downloaded as compressed plain text files and the information can be extracted using the command-line interface tools provided.  There is also a Java-based graphical user interface (GUI) application available that is able to process the compressed plain text files, which allows a search and a display of the information.  This GUI application supports different languages, but the movie related data is in English, as made available by IMDb. A Python package called IMDbPY can also be used to process the compressed plain text files into a number of different SQL databases, enabling easier access to the entire dataset for searching or data mining. 
The IMDb has sites in English as well as versions translated completely or in part into other languages ( Danish, Finnish, French, German, Hungarian, Italian, Polish, Portuguese, Spanish and Romanian). The non-English language sites display film titles in the specified language. Originally, IMDb's English language sites displayed titles according to their original country-of-origin language, however, in 2010 IMDb began allowing individual users in the UK and USA to choose primary title display by either the original-language titles, or the US or UK release title (normally, in English).
User ratings of films
IMDb indicates that submitted ratings are filtered and weighted in various ways in order to produce a weighted mean that is displayed for each film, series, and so on. It states that filters are used to avoid ballot stuffing ; the method is not described in detail to avoid attempts to circumvent it. In fact, it sometimes produces an extreme difference between the weighted average and the arithmetic mean.
The IMDb Top 250 list is a listing of the top rated 250 films of all-time, based on ratings by the registered users of the website using the methods described. As of 30 September 2017, The Shawshank Redemption is #1 on the list.  The 'top 250' rating is based on only the ratings of "regular voters". The exact 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. Though the current formula is not disclosed, IMDb originally used the following formula to calculate their weighted rating:  
- = weighted rating
- = average for the movie as a number from 1 to 10 (mean) = (Rating)
- = number of votes for the movie = (votes)
- = minimum votes required to be listed in the Top 250 (currently 25,000)
- = the mean vote across the whole report (currently 7.0)
The 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 1500 votes must be received to qualify for the list. 
The top 250 list comprises a wide range of feature films, including major releases, cult films, independent films, critically acclaimed films, silent films and non-English language films. Short films and TV episodes are not included.
Since 2015, there has been a Top 250 list devoted to ranking television shows. 
Beginning in 2001, the Internet Movie Database also maintained message boards for every title (excepting, as of 2013, TV episodes  ) and name entry, along with over 140 main boards. This began in 2001. In order to post on the message boards a user needed to "authenticate" their account via cell phone, credit card, or by having been a recent customer of the parent company Amazon.com. Message boards expanded in recent years. The Soapbox started in 1999 as a general message board meant for debates on any subjects. The Politics board started in 2007 was a message board to discuss politics, news events, and current affairs, as well as history and economics.
As of February 20, 2017, all the message boards and their content have been permanently removed. According to the website, the decision was made because the boards were "no longer providing a positive, useful experience for the vast majority of our more than 250 million monthly users worldwide".  Col Needham also mentioned in a post some months earlier that the boards received less income from ads, and that their members only made up a very small part of the website's visitors. The boards were costly to run due to the system's age and dated design, which did not make business sense.  The decision to remove the message boards was met with outspoken backlash across the web and on social media, and sparked an online petition garnering over 8,000 signatures.  In the days leading up to February 20, 2017, both Archive.org  and MovieChat.org  preserved the entire contents of the IMDb message boards using web scraping technologies.
In 2011, in the case of Hoang v. Amazon.com , IMDb was sued by an anonymous actress for more than US$ 1,000,000 due to IMDb's revealing her age (40, at the time).  The actress claimed that revealing her age could cause her to lose acting opportunities.  Judge Marsha J. Pechman, a U.S. district judge in Seattle, dismissed the lawsuit, saying the actress had no grounds to proceed with an anonymous complaint. The actress re-filed and so revealed that she was Huong Hoang of Texas, who uses the stage name Junie Hoang.  In 2013, Pechman dismissed all causes of action except for a breach of contract claim against IMDb; a jury then sided with IMDb on that claim.  The Court of Appeals for the Ninth Circuit affirmed the district court judgment in March 2015. 
Also in 2011, in the case of United Video Properties Inc., et al. v. Amazon.Com Inc. et al.,  IMDb and Amazon were sued by Rovi Corporation and others for patent infringement over their various program listing offerings.  The patent claims were ultimately construed in a way favorable to IMDb and Rovi/United Video Properties lost the case, though as of November 2014 it is on appeal. 
On January 1, 2017, the State of California implemented state bill AB-1687, a SAG-AFTRA -backed anti-ageism statute which requires "commercial online entertainment employment services" to honor requests by their subscribers for their ages and birthdays to be hidden.  On February 23, 2017, Judge Vince Girdhari Chhabria issued a stay on the bill pending a further trial, claiming that it possibly violated the First Amendment because it inhibited the public consumption of factual information. He also questioned the intent of the bill, as it was ostensibly meant to target IMDb. 
As of the beginning of 2017, IMDb has received 2,300 requests from individuals to remove their date of birth from the site. Included in this group were 10 Academy Award winners and another 71 who’ve been nominated for Oscars, Emmys, or Golden Globes. 
- AllMusic – a similar database, but for music
- All Media Network – a commercial database launched by the Rovi Corporation that compiles information from the former services AllMovie and AllMusic
- Big Cartoon DataBase
- DBCult Film Institute
- Internet Adult Film Database
- Internet Movie Cars Database (IMCDb)
- Internet Movie Firearms Database (IMFDb)
- Internet Book Database (IBookDb)
- Internet Broadway Database (IBDb)
- Internet Off-Broadway Database (IOBDb)
- Internet Speculative Fiction Database (ISFDb)
- Internet Theatre Database (ITDb)
- List of films considered the best
- List of films considered the worst
- Rotten Tomatoes