Zork is a text adventure game. It was first released in 1977. The developers were Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling. They created it for the PDP-10 mainframe computer. Later, the original developers and others formed a company called Infocom. They expanded the game and split it into three titles: Zork I: The Great Underground Empire, Zork II: The Wizard of Frobozz, and Zork III: The Dungeon Master. These titles were released for personal computers starting in 1980. In Zork, the player explores an abandoned underground empire to find treasure. The game has hundreds of locations. Players type commands in natural language to move and interact with objects. The program describes the player's location and the results of their actions. Zork is considered the most famous example of interactive fiction.
The original game was developed between 1977 and 1979 at the Massachusetts Institute of Technology (MIT). It was inspired by Colossal Cave Adventure (1976), the first well-known adventure game. The developers wanted to create a game that could understand more complex sentences than the two-word commands used in Adventure. In 1979, they founded Infocom with colleagues from the MIT computer center. Marc Blank and Joel Berez developed a way to run part of Zork on microcomputers, allowing the game to be sold commercially. The first episode was published by Personal Software in 1980. Later, Infocom bought the rights and self-published all three episodes starting in late 1981.
Zork became very successful for Infocom. Sales increased as personal computers became more popular. The first episode sold over 38,000 copies in 1982 and about 150,000 copies in 1984. Together, the three episodes sold more than 680,000 copies by 1986. These sales made up more than one-third of Infocom’s total sales during that time. In 1986, Infocom was purchased by Activision. This led to new Zork games released in 1987 and a series of books. Reviews of the games were very positive, with many calling Zork the best adventure game of its time. Critics consider it one of the greatest video games ever made. Historians note that Zork helped shape the adventure game genre and influenced the development of MUD and massively multiplayer online role-playing games. In 2007, Zork was added to the Library of Congress’s list of the ten most important video games in history.
Gameplay
Zork is a text-based adventure game where players explore the ruins of the Great Underground Empire. Players type commands to move through locations, solve puzzles, and collect treasure. The game includes hundreds of locations, each with a name and description. Commands can be short, like "get lamp" or "north," or longer, like "put the lamp and sword in the case." Commands must match the situation in a location (for example, "get lamp" only works if a lamp is present). The game acts as a narrator, describing the player's surroundings and the results of their actions. If the game does not understand a command, it asks the player to retype it. The game's responses are often playful and teasing, similar to how a game leader might speak in a tabletop role-playing game.
The original version of the game, released in 1977, was called Zork. When it became a commercial product, it was split into three parts. The second and third parts added new and expanded areas. Many areas in the game require solving puzzles, such as pressing buttons on a dam or navigating a maze. Some puzzles have more than one solution. For example, in the "Loud Room," players can either stop water from falling by emptying a nearby dam or shout "echo" to change the room's acoustics. In the first part, called Zork I, a thief moves through the underground, taking items left behind or stealing from the player. Players can fight or avoid the thief and recover stolen items from the thief's treasure room. Some areas have enemies that players must fight or overcome. In Zork II, players can learn magic spells to use in puzzles and battles. In dark areas, players must carry a light source, like a lantern, to avoid being attacked by a monster called a grue. The amount of items a player can carry is limited by their total weight, not the number of items.
A main goal in each part is to collect all treasures, which are often hidden behind puzzles. As players collect treasures or complete tasks, their score increases, showing how much of the game they have finished. Players can explore and solve puzzles in any order, though some paths require solving puzzles first. In Zork III, a timed event affects the game's outcome: an earthquake happens after about 130 moves, changing passageways. In each part, treasures are needed to complete the game.
Plot
Zork does not follow a story that happens in a single, clear order. Most of the game’s setting is described through written details about items and places, as well as manuals added in later versions. Long before the game’s events, the Quendor empire took over all areas above ground and built a large cave system to expand. Two hundred years later, the ruler, Lord Dimwit Flathead, changed the empire’s name to the Great Underground Empire. During his rule, he spent time and resources on big projects, like an underground dam and a royal museum, which were not very useful. A century later, the empire’s spending too much money caused it to fall apart, and all the people left. The empty empire is the setting for the three parts of Zork.
Zork I begins with the player standing in an open field west of a white house with a closed door. Most of the game takes place underground, as do the other parts. The player must find all 20 treasures and place them in a trophy case to receive an ancient map and win the game. In Zork II, the player learns about the Flatheads and meets the Wizard of Frobozz, a powerful magician who was forced to leave by Lord Dimwit Flathead when his magic weakened. The wizard appears at random times during the game and casts spells that start with the letter “F” on the player. These spells have effects, such as making the player glow or freezing them in place for a few turns. To finish the game, the player must obtain a wand from the wizard. In Zork III, the player gathers the clothing of the Dungeon Master to become their replacement. After collecting all items, the player must give food to an old man who reveals himself as the Dungeon Master and shows the way to the final hallway. Once the player solves the last puzzles and reaches the Treasury of Zork, the Dungeon Master appears, changes the player’s appearance to look like himself, and disappears, ending the trilogy.
The 1977 version of the game is mostly similar to Zork I but includes additional areas, puzzles, and treasures that later appeared in Zork II and Zork III. It also features the Puzzle Room and the ending that became part of Zork III. After collecting all 32 treasures, the Dungeon Master invites the player to the Tomb of the Unknown Implementor, leading to the game’s final ending.
Development
In May 1977, Tim Anderson, Marc Blank, Bruce Daniels, and Dave Lebling started working on a game called Zork. These four people were part of the Dynamic Modelling Group, a research team at the Massachusetts Institute of Technology (MIT) Laboratory for Computer Science. Anderson, Blank, and Daniels were students, while Lebling was a research staff member. Their work was inspired by a game called Colossal Cave Adventure, which was the first well-known example of interactive fiction and the first well-known adventure game. This game was very popular among computer users at the time and became a big hit at MIT in early 1977. By the end of May, players had solved the game completely.
The four programmers wanted to create a better text adventure game. They planned to use more complex inputs than the two-word commands in Adventure and make puzzles easier to understand. They believed their MDL programming language was better for handling complex text than the Fortran code used in Adventure. The group had experience with video games: Blank and Anderson had worked on a trivia game called Trivia (1976), and Lebling was involved in Maze (1973), a 3D first-person game. Lebling first created a parser, a system that could process typed two-word instructions. Anderson and Blank built a small prototype text game to use it. The prototype was created for the Digital Equipment Corporation (DEC) PDP-10 mainframe computer, the only system that supported their programming language.
While Lebling was on vacation, Anderson, Blank, and Daniels designed an adventure game concept, which Anderson and Blank then developed as an early version of Zork. This prototype included simple versions of ideas seen in the final game, such as puzzles and locations. Anderson said it took time for people to learn how to write good problems, and Lebling’s first parser was only "almost as smart as Adventure’s." The game had no name at first, but the group often called their programs "zork" until they were completed, a term used at MIT for in-development programs. After Lebling returned, the group continued working on the game, improving the parser and adding features through June 1977. Grues were added to replace pits that would kill players in the dark; during play-testing, Lebling noticed his character fell into a pit in the attic of a house.
Lebling said Adventure was one of Zork’s only influences, as few other games existed at the time. Although the game’s combat was based on Dungeons & Dragons, Lebling said the other developers had never played it. He also thought the parser and text responses acted like the Dungeon Master from a Dungeons & Dragons game, guiding players through the story by describing it. This idea had also been used in Adventure.
The developers did not announce their game during development, but a lack of security on MIT systems allowed anyone with access to the PDP-10 computer over the ARPANET to see what programs were being run. A small group of people, many of whom had played and contributed to Trivia, discovered the new "Zork" game and spread the word. This community, which included dozens or hundreds of players, interacted with the developers as they created the game, testing additions and reporting bugs. The developers added a command transcript feature to track commands players tried but failed to use.
By the end of June, the game was about half the size of the final Zork and had a large community of players. The group added locations like a volcano and coal mine, and later focused on improving the game’s engine and adding the ability to save progress. They also made the game compatible with different operating systems, TENEX and TOPS-20, which were more popular than the system used at MIT. These users created a mailing list to share updates. In the fall of 1977, the developers added the "Alice in Wonderland" section and a system for fighting enemies.
Around this time, a DEC employee named Ted Hess decoded the group’s protections for the source code, and another employee, Bob Supnik, created a version of the game in Fortran. This version, released in March 1978, allowed more players without access to a PDP-10 to play the game. At this point, the team gave the game a real name, "Dungeon," which was used for the Fortran version. However, TSR Hobbies claimed the name violated their trademark for Dungeons & Dragons, so the developers returned to using "Zork."
In 1978, the team added sections like the bank and Royal Zork Puzzle Museum, along with puzzles and ideas suggested by players. The last puzzle was added in February 1979, though the team continued releasing bug fixes until January 1981. Anderson said this was because the team ran out of ideas, time, and space in the one megabyte of memory allocated for the game.
Very little of the game was planned in advance, and no part of it was specific to one developer. When a developer had a good idea, they added it to the game, developing the concept and writing the text for it. Lebling said Blank focused on the parser, Anderson on the game code, Blank and Daniels on puzzles, and Lebling on location descriptions. Anderson said Blank wrote "40 or 50" versions of the parser, and Daniels designed puzzles that others implemented. Blank handled vehicles and saving
Reception
After its release in 1980, Zork I became a bestseller from 1982 to 1985, with 380,000 copies sold by 1986. In its first nine months, Personal Software sold 7,500 copies for the TRS-80 and Apple II. Sales increased a lot when Infocom began publishing the trilogy themselves and the personal computer market grew. By the end of 1982, Zork I had sold 38,000 copies, nearly 100,000 in 1983, and about 150,000 in 1984. Its success was greater than Infocom’s later games; in 1983, Inc. reported that Zork I, one of Infocom’s fifteen released titles, made up 20% of their annual sales. Zork I sales decreased starting in 1985. The second and third parts of Zork also sold well, though not as much as the first: more than 170,000 copies of Zork II and 130,000 copies of Zork III were sold by 1986.
Combined sales of the first three Zork episodes reached 250,000 copies by 1984, more than 680,000 copies through 1986, including the 1986 Zork Trilogy compilation release, and over 760,000 copies by early 1989. Between 1982 and 1986, the Zork trilogy made up more than one-third of Infocom’s total sales of 2 million games. Activision bought Infocom in 1986 and reported that the three Zork games and trilogy compilation sold an additional 80,000 copies by early 1989.
Reviewers praised the Zork episodes for their writing and gameplay. Byte and 80 Micro highlighted the game’s “entertaining, eloquent, witty, and precise” writing. Softalk and The Space Gamer noted that the game’s parser allowed players to input more complex sentences than earlier games, though they suggested players might still prefer simpler two-word commands. 80 Micro questioned whether Zork could be completed due to the parser’s flexibility. Byte called Zork “the boldest and most exciting advance in Adventure games,” a view shared by Softalk.
After its release, Zork I received more praise for its connection to the Adventure genre. Jerry Pournelle described the mainframe and Personal Software versions as “more difficult and more interesting” than Adventure in 1980, and recommended the Infocom version in 1983, saying that “if you liked Adventure and wanted more… I guarantee you’ll love Zork.” Computer Gaming World, PC Magazine, and SoftSide all recommended Zork I as a “must-have” for fans of fantasy or adventure games. Family Computing called it a classic of the genre and the game that made adventure games more than a novelty.
Reviewers also praised Zork II and III. Softline recommended Zork II for its “well-balanced mix of humor, wit, and wry puns.” PC Magazine said it was challenging, enjoyable, and funny. Softalk noted that Zork II was “fresh and interesting” compared to the first episode and Adventure. Some puzzles in Zork II were later called “infamously difficult,” and Infocom apologized in a hint book for one puzzle’s reliance on baseball knowledge. Softalk and Creative Computing named Zork III the best in the trilogy. PC World said it was “just as exciting and puzzling as Zork I and II,” though its puzzles could be frustrating. Fantasy Gamer called it “possibly the ultimate in all-text adventure games,” and K-Power said Zork III was “the most intelligent text game for a microcomputer that we’ve ever seen.”
Commodore Magazine described the combined trilogy as the most popular and best adventure game in 1983. The Addison-Wesley Book of Atari Software 1984 gave all three Zork games an A+ rating. It called Zork I “the definitive adventure game,” said Zork II had “the same outstanding command flexibility, wry humor, and word recognition of Zork,” and concluded that Zork III was “perhaps the most entertaining of the three” and “a highwater mark for subtlety and logic.” InfoWorld’s Essential Guide to Atari Computers recommended the trilogy as among the best adventure games for the Atari 8-bit computer.
Legacy
Zork is often called "the most famous piece of interactive fiction" and "the father of the genre." Game historian Matt Barton said that Zork's influence on adventure games is similar to how the ancient poem The Iliad has influenced poetry. Barton explained that Zork showed how computers could create rich, imaginary worlds and helped shape ideas in video games, such as exploring, collecting items, and solving problems. In his book Twisty Little Passages (2003), Nick Montfort noted that Zork's lasting impact came from how it created a detailed, changing game world that players could move through. Janet Murray, in Hamlet on the Holodeck (1997), explained that Zork's design, which treated each area, item, and character as separate objects, made it stand out compared to other games of its time. Historians say that Zork, along with Colossal Cave Adventure, helped create the MUD genre, which later influenced modern multiplayer online games.
Zork's natural language parser, which allowed players to type commands, was noted for its unique personality. It was one of the first games to use this feature and inspired later adventure games to include humor and self-references in their writing. Even today, Zork is seen as an inspiration for text-based systems like chatbots and has been used to test how computers understand human language.
Zork was recognized as one of the best video games many years after its release. In 1992, Computer Gaming World added Zork to its Hall of Fame. It was listed on "best games of all time" lists by Computer Gaming World and Next Generation in 1996, and Next Generation included the entire Zork series in 1999. In 2016, PC Gamer ranked Zork as one of the 50 most important video games ever made for helping establish Infocom as a studio and defining a generation of adventure games. In 2007, the Library of Congress added Zork to its "game canon" list for preservation. In November 2025, Microsoft, which had bought Activision, released Zork I, II, and III as open-source software.
The grue, a mysterious creature in Zork, has been referenced in other games like NetHack, World of Warcraft, and Alan Wake. A song by rapper MC Frontalot, titled "It Is Pitch Dark," also mentions the grue. Writer Bernard Perron said that being hunted by a grue was a unique and terrifying experience for players. IGN called the grue one of the best video game villains, noting that the line "It is pitch black. You are likely to be eaten by a grue" was effective. Even though the grue's appearance was later described, players often imagine it in their own way. The grue started as a solution to a game problem but became a famous symbol in early video game history.
Zork was the most important game in Infocom's collection. After Zork, Infocom released many other text adventure games using the same codebase and Z-machine. These games sold tens of thousands of copies. By 1984, three years after Infocom began publishing Zork, the company had 50 employees, $6 million in annual sales, and 12 other games. Infocom nicknamed some of its early games based on Zork, such as Deadline (1982) as "Zork: The Mystery" and Enchanter (1983) as Zork IV. By 1986, Infocom had released 26 games. Although Wishbringer (1985) was set in the same world as Zork, the company did not make any more official Zork games after that, only a compilation of the original three.
In 1985, Infocom expanded into professional software by creating a product called Cornerstone, a relational database. Poor sales led to financial problems, and the company was sold to Activision in 1986. Under Activision, Infocom released two more Zork games: Beyond Zork: The Coconut of Quendor (1987), which added maps and role-playing elements, and Zork Zero: The Revenge of Megaboz (1988), a prequel with graphical features. However, Activision closed Infocom in 1989 due to rising costs and declining profits.
Activision later released several graphic adventure games based on Zork, including Return to Zork (1993), Zork Nemesis: The Forbidden Lands (1996), and Zork: Grand Inquisitor (1997). A free text adventure game, Zork: The Undiscovered Underground (1997), was also released to promote Zork: Grand Inquisitor. In 2009, Legends of Zork, a browser-based game, was released by Jolt Online Gaming.
The original Zork games have been re-released in many compilations, including The Lost Treasures of Infocom (1991), Zork Anthology (1994), and Zork Legacy Collection (1996). A graphical version of Zork I was made for the PlayStation and Sega Saturn in 1996, 19 years after its original release. Unofficial versions of Zork have been created for many systems over the years, including browsers and smart speakers.
Four gamebooks set in the Zork world were published between 1983 and 1984: The Forces of Krill (1983), The Malifestro Quest (1983), The Cavern of Doom (1983), and Conquest at Quendor (1984). These books, known as the "Zork books," are written like Choose Your Own Adventure books, where players make choices and turn to pages based on those choices. Two novels based on Zork were published: The Zork Chronicles by George Alec Effinger (1990) and The Lost City of Zork by Robin Wayne Bailey (1991). In 1996, Threshold Entertainment acquired the rights to Zork and planned a movie and TV series, though neither was made.