Since Duke Nukem 3D v0.99 Beta was leaked during the early days of the Internet, it is difficult to find any information about the timing of the initial leak or whether it was widely downloaded. However, it is known that the beta was compiled on January 4th, 1996, and it was leaked by a video game critic who received an advance copy of the game to review for a magazine. Apparently unknown to the reviewer, the leak included a file named "README.TXT" with a note from developer George Broussard that is addressed to the reviewer, thus incriminating the reviewer as the source of the leak.
This prototype is only one of a few publicly available Duke Nukem 3D prototypes. Other downloadable prototypes include LameDuke and version 1.0 of the shareware version, the latter of which was released in advance of the commercial version and is noticeably different from it. There are existing screenshots and videos from several unreleased prototypes as well.
Duke Nukem 3D v0.99 Beta was compiled on January 4th, 1996, which was less than a month before the release of shareware version 1.0 on January 29th and a few months before the commercial release on April 24th.
The prototype is nearly identical to the completed game, but there are many notable differences from the final product. Key differences include the following:
- Five difficulty settings (Easy, Medium, Normal, Hard, and Headache) instead of only four
- Different episode and level names
- Minor modifications to most of the map layouts
- Significantly less health for many of the enemies
- The Chaingun Cannon has a faster rate of fire and deals less damage per bullet
- An unused Flamethrower weapon (only partially coded)
- An unused Space Suit item for the inventory (only partially coded)
- Two unused enemies, the Snake Head and the Organic Turret (only partially coded)
It is possible to unlock the Shrinker, Flamethrower, and Laser Tripbombs by using the "dnweapons" and "dnammo" cheats. After depleting all ammo with all other weapons, the game will automatically switch to the Shrinker. The Shrinker lacks a first-person sprite, and its projectiles will shrink enemies that are several meters away from the blasts, giving it a much larger blast radius than in the final version. When all of the Shrinker ammo is depleted, the game will automatically switch to the Flamethrower. The Flamethrower also lacks a first-person sprite, and it uses the Freezethrower's sound effects. It does not fire projectiles but is instead an automatic hitscan weapon. When hit, enemies will acquire an enlarged aura around their sprites, and a flame will appear on the ground beneath them. Enemies explode when killed by the Flamethrower. When the Flamethrower's ammo is depleted, the game will automatically switch to the Laser Tripbombs, which are indistinguishable from those in the final game. The Devastator does not exist in this version of the game.
- dngodly: enables God Mode
- dnungodly: disables God Mode
- dnweapons: gives all weapons
- dnammo: gives full ammo for all weapons
- dnitems: gives all Access Cards and inventory items
- dnclip: toggles clipping on/off, allowing the player to move through walls
- dnwarpXY: warps to a different level, corresponding to episode number X and level number Y
- dnskillX: restarts the level at difficulty setting X, where X is a number between 0 and 9
- dnunlock: opens all doors
- dnview: toggles between first-person and third-person views
- dnrate: toggles on/off two statistics in the top-left corner of the screen, possibly measuring the frame rate
- dnhyper: activates the Steroids
- dnending: plays the level-end sequence for The Abyss
In 2012, Duke Nukem forum users Marcos, LakiSoft, and Linush developed a mod named Duke Nukem 3D Beta 0.99 Recreation. The mod includes the leaked prototype, as well as backwards-compatible versions of all levels from the commercial release. It also includes a fully functional Flamethrower and Space Suit, features that were only partially coded in the original 0.99 prototype.