The Half-Life and Portal series has spawned countless user-created modifications, or mods, including many that have become highly popular in their respective communities. Some original mods for Half-Life games, such as Counter-Strike and Day of Defeat, have since had their rights acquired by Valve and turned into standalone releases. Other Half-Life mods, such as Team Fortress Classic (originally a Quake mod redeveloped on the GoldSrc engine) and Ricochet, were created and distributed by Valve themselves. Although Valve have a long history of hiring from mod communities, some mods for Half-Life games, such as The Ship and Natural Selection, have been developed into standalone releases or franchises by independent teams without Valve's involvement.
Some notable mods for Half-Life and Portal games, such as Missing Information, are based on cut content or concepts found in the game's files or in the Half-Life 2 leak. Other mods include minor or major alterations to the game in question, while others can be considered total conversions, containing new maps that have been made entirely from scratch, only utilizing the existing engine, models, sounds, textures, et cetera. Non-commercial mods can be legally downloaded for free, as they are not licensing the engine.
Action Half-Life is a multiplayer mod for Half-Life that simulates fast and frenetic gun combat similar to what is seen in action films, especially films directed by John Woo.
Afraid of Monsters is a survival horror-themed single-player modification for Half-Life developed by Team Psykskallar, who would later go on to develop Cry of Fear. It is played from the point of view of David Leatherhoff, a man addicted to drugs who begins experiencing fearsome illusions in the psychiatric hospital he has been kept in.
Counter-Strike (originally marketed as Half-Life: Counter-Strike) is a multiplayer first-person shooter initially created by Minh Le and Jess Cliffe as a mod for Half-Life but eventually turned into a retail game developed by Valve. Counter-Strike focuses on conflicts between a team of terrorists who try to perpetrate an act of terror (bombing, hostage-taking, or assassination) while a team of counter-terrorists try to stop them.
Azure Sheep is a single-player modification for Half-Life in which the player assumes the role of a member of the Black Mesa Security Force. When the Black Mesa Incident occurs, he embarks on a mission to save his colleague, Kate, who is trapped elsewhere in the facility.
Black Ops is a single-player mod for Half-Life in which the player assumes the role of agent Declan Walker, a member of the Black Ops who is sent on a mission to eliminate a scientist and arm the Mark IV Thermonuclear Device.
Cat-Life is a single-player mod for Half-Life in which the player enters the mind and body of an ordinary house cat who finds himself in the Black Mesa Research Facility during the incident.
Cry of Fear
Cry of Fear is a single-player psychological horror first person shooter game made by Team Psykskallar, who previously created the Afraid of Monsters mod for Half-Life. Cry of Fear was originally developed as a modification for Half-Life, but was released as a standalone title available on Steam.
Its story begins with 19-year-old Simon Henriksson waking up in an unknown alley shortly after being hit by a car. Much of his time is spent exploring his surroundings and fighting off crazed, deformed humanoid creatures. He also receives flashbacks that tell the story of what happened after the accident, varying from the police response to his resulting hospital stay.
Day of Defeat is a team-based multiplayer first-person shooter mod for Half-Life that is set in the European theatre of World War II around the year 1944. Though originally a third-party modification, Valve acquired the intellectual property rights of Day of Defeat and re-released it as a retail game in 2003. A remake of Day of Defeat on the Source engine was developed by Valve and released in 2005 as Day of Defeat: Source.
Deliverance is a single-player modification that continues the story of Gordon Freeman following the end of Half-Life.
Drug Barons is a single-player level pack for Half-Life by Maverick Developments released in March 1999. It takes place after the events of Half-Life, where Gordon Freeman accepts the G-Man's offer and joins the government department that he works for. Back on Earth, the G-Man gives Gordon a mission to destroy a drug factory located in a remote South American location.
Half-Life: Echoes is a single-player modification for Half-Life that revisits the Black Mesa Incident, with a strong emphasis on horror.
Half-Life: Visitors is a single-player modification for Half-Life. It is played from the point of view of Dr. Alan Green, a young lawyer who was sent to the Black Mesa desert as a safety evaluator to carry out an inspection of Black Mesa.
Half-Life: Induction is a prequel to Half-Life in which the player assumes the role of Gordon Freeman.
Natural Selection is a multiplayer Half-Life modification that combines first-person combat with real-time strategy elements. It features "marines versus aliens" teamplay, where one marine can become a commander, who plays from a top-down perspective and leads live players, while aliens can evolve and change lifeforms to run on walls, fly, or devour marines whole. On 31 October 2012, a standalone sequel to Natural Selection was released, titled Natural Selection 2.
PARANOIA is a total conversion single-player modification for Half-Life that is played from the point of view of a Russian military officer.
Peaces Like Us is a single-player modification for Half-Life, set in a world where mankind is allied with the aliens of Xen.
In Point of View, a single-player modification created by the author of Azure Sheep, the player enters the body of a Alien Slave named Xonxt. The game starts as humans invade Xen and capture the XTBS, an important piece of Xen technology. The game follows this Vortigaunt's journey as it attempts to recapture the device. Point of View features new weapons as well as both old and new areas of the Black Mesa Research Facility and Xen.
Redemption is a single-player modification for Half-Life that was developed by Maverick Developments and released in October 1999. Another version of the mod titled Absolute Redemption was included with the original retail version of Counter-Strike that was released in November 2000.
Redemption takes place after the events of Half-Life, where Gordon Freeman has accepted the G-Man's offer. Now an agent, Gordon is assigned to retrieve three Telnorps and return them to Xen.
Ricochet was originally a multiplayer mod for Half-Life that was developed by Valve, who later released it as a standalone retail game on Steam. Ricochet is notable for its apparent simplicity, inspired by arcade and platform games in both concept and design. Players jump between neon-lit platforms suspended above an abyss and shoot disks at one another, trying to push the opponent off the platform and into the depths.
Scientist Slaughterhouse is a single-player modification of Half-Life that allows the player to murder scientists in many different, often humorous, ways without any consequences.
Sven Co-op is a multiplayer cooperative modification for Half-Life in which players must work together against AI-controlled enemies and solve puzzles as a team. It is one of the oldest Half-Life mods to still be actively updated.
Sweet Half-Life is a single-player mod for Half-Life, set at a similar time to the original game and following a similar storyline. It is played through the eyes of Gordon McGinley, and follows his plight to escape from the crumbling Black Mesa Research Facility.
Team Fortress Classic is a class- and team-based multiplayer first-person shooter mod for Half-Life that was developed by Valve and released for Windows on April 1, 1999. It is a remake of Team Fortress, a mod that was developed by Australian modders Ian Caughley, John Cook, and Robin Walker for the video game Quake in 1996. Team Fortress Classic was created after Valve purchased the rights to the Team Fortress mod and hired Cook and Walker to remake it on the Half-Life engine. In 2007, Team Fortress Classic was followed by a standalone Source engine sequel titled Team Fortress 2.
The Ship is a multiplayer mod for Half-Life that takes place on a ship where players must inconspicuously murder given targets without being detected as the murderer. The Ship was later developed into a retail game running on the Source engine.
The Specialists is a multiplayer modification for Half-Life that features gun combat inspired by action films. Originally intended to be a mod where players would work in teams, The Specialists instead evolved into a free-for-all deathmatch mod.
They Hunger is a single-player horror mod for Half-Life developed by Black Widow Games. Taking place in a small American town in the 1950s, the player assumes the role of an author who attempts to escape when he finds that the town has been overrun by zombies.
TWHL Tower is a single-player mod for Half-Life that was collaboratively created by members of The Whole Half-Life (TWHL) community.
USS Darkstar is a single-player Half-Life mod created by Neil Manke and his team, largely based in Canada. The mod follows Gordon Freeman and several other scientists aboard the USS Darkstar, a large exploratory starship, in the year 2066.
Wanted! is a single-player and multiplayer total conversion for Half-Life, played from the point of view of Sheriff Rogan Black.
1187 is a single-player Half-Life 2 mod that takes place in Amstelveen, Netherlands during the Portal Storms.
Age of Chivalry is a total conversion multiplayer modification for Half-Life 2 developed by Team Chivalry.
Aperture Tag: The Paint Gun Testing Initiative
Aperture Tag: The Paint Gun Testing Initiative is a Portal 2 modification based on the game Tag: The Power of Paint. It features the Aperture Science Paint Gun Device - a tool capable of spreading out an unlimited amount of Repulsion or Propulsion Gel - instead of the regular Portal Gun.
Awakening is a single-player Half-Life 2 mod that continues the story of Half-Life: Opposing Force and is set before Half-Life 2.
Black Mesa is both a third-party total conversion mod for Half-Life 2 and remake of the original Half-Life. The ultimate goal of the mod is to recreate the original Half-Life from the ground up, using the advanced capabilities of the Source engine to create a new and more engrossing in-game world with more varied, complex environments and more challenging, realistic gameplay.
The Citizen is a series of single-player mods for Half-Life 2, set in a storyline parallel to the original game. The player takes the role of an ordinary man who is pushed over the edge by the oppressive regime controlling his life. His home trashed, his family dead, the Citizen leaves his apartment for the last time. He seeks new friends and a way to help the human resistance smash the iron grip of the Combine. What follows is a winding tale of betrayal, determination and grief. Many obstacles lie in his path which require a sleek combination of agility, stealth, intelligence, and sheer violence to overcome.
Coastline to Atmosphere is a single-player mod for Half-Life 2, released in 2006, that continues the story of the game.
Combine Destiny is a single-player Half-Life 2 mod played from the point of view of a Combine Soldier.
Dark Interval is a single-player modification based on content cut from Half-Life 2 that was found in the Half-Life 2 leak.
DayHard is a comedic single-player Half-Life 2 mod set before the events of Half-Life 2. In DayHard, the player assumes the role of Gordon's brother, Morgan Freeman.
Dear Esther is a first-person art video game that was released in June 2008 as a free Source mod and later redeveloped for a commercial release in February 2012. The game does not follow traditional video game conventions, as it involves minimal interaction from the player and does not require choices to be made nor tasks to be completed. It instead places focus on its story, which is told through a fragmented, epistolary narrative as the player explores an unnamed island in the Hebrides.
Dino D-Day is a multiplayer team-based total conversion modification developed on the Source engine. Players can battle online, choosing to serve either the Allied nations or the Nazis during World War II, with both sides aided by resurrected dinosaurs.
D.I.P.R.I.P. is a multiplayer total conversion modification for Half-Life 2. It is set in various post-war environments and focuses on vehicular combat.
Dystopia is a multiplayer cyberpunk-themed mod for Half-Life 2.
Entropy : Zero
A mod for Half-Life 2 taking place from the perspective of a Civil Protection officer nicknamed “Bad Cop”.
FakeFactory's Cinematic Mod
FakeFactory's Cinematic Mod is a modification that aims to improve the graphics of Half-Life 2 and its episodes, and push the Source engine's capabilities as far as possible.
HD Alyx model based on Brazilian model Adriana Lima in Version 8 of FakeFactory's Cinematic Mod.
The Overwatch Nexus in Version 10.
Garry's Mod is a sandbox game that was originally released as a modification for Half-Life 2 before Valve partnered with the developer, Garry Newman, to publish it as a standalone commercial release on Steam. Garry's Mod allows the player to manipulate physics props from most of Valve's Source engine games and experiment with the physics of the Source engine, often with interesting results due to the quirks of the engine. Being a sandbox game, there is no goal as such, nor a way to "win"; instead, users are encouraged to play the mod however they wish, develop their own add-ons, and share their creations via the Steam Workshop. Many different customized gamemodes have been developed for Garry's Mod, with many different objectives and styles.
Eternal Silence is a cinematic multiplayer Source engine modification that takes place in outer space.
GoldenEye: Source is a total conversion modification of Half-Life 2, and a remastered verison of the original GoldenEye64.
Guard Duty is an upcoming remake of Half-Life: Blue Shift on the Source engine.
Half-Life 2 Capture the Flag is a multiplayer modification of Half-Life 2 that centers around the titular game mode.
Half-Life 2: Riot Act is a single-player modification for Half-Life 2. It is played from the point of view of Jamil Lee, a young member of the civilian Resistance who is taken by the Combine and imprisoned in Nova Prospekt.
Half-Life 2: Short Stories: Human Error is a Half-Life 2: Episode One modification in which the player assumes the role of a Civil Protection officer called Anders.
Lambda Wars, previously known as Half-Life 2: Wars, is a multiplayer Source engine modification that brings the war between mankind and the Combine to a real-time strategy setting.
MINERVA is an episodic single-player modification for Half-Life 2 created by Adam Foster. It is a follow-up to Someplace Else, a mod that Foster previously created for Half-Life.
Missing Information is a single-player modification based on the cut content found in the Half-Life 2 leak.
Mistake of Pythagoras
Mistake of Pythagoras is a single-player modification for Half-Life 2 developed by the creator of Sweet Half-Life. The player assumes the role of Gordon Freeman in a parallel universe.
Nuclear Dawn is a post-apocalyptic first-person shooter real-time strategy hybrid video game, originally announced in February 2006 as a mod for the Source engine. In April 2009, it was revealed to have become a commercial project, still using Source. It was released on September 26, 2011.
Obsidian Conflict is a community-based multiplayer mod for Half-Life 2 and its episodes that features cooperative gameplay.
Operation Black Mesa
Operation Black Mesa is an upcoming modification for Half-Life 2 that seeks to remake Half-Life: Opposing Force on the Source engine.
Portal: Prelude is a single-player modification for Portal that aims to extend the Portal storyline.
Portal Stories: Mel
A single-player modification for Portal 2 that explores the story of Mel, a character cut from Portal 2.
Portal: The Flash Version MapPack
Research and Development is a puzzle-centric single-player mod for Half-Life 2: Episode Two.
SMOD is a single-player modification that adds new effects, weapons, and NPCs to Half-Life 2.
SourceForts is a team-based multiplayer mod for Half-Life 2: Deathmatch in which opposing teams can build bases and other structures with props within a "build phase" before trying to capture the enemy team's flag in a "combat phase".
Synergy is a co-operative multiplayer modification for Half-Life 2, Lost Coast, Episode One, Episode Two, and SiN Episodes: Emergence. It also includes fan-made cooperative maps, as well as support for the mods MINERVA, Half-Life 2: Riot Act and City 7: Toronto Conflict. It is available for download on Steam.
One of the first Half-Life 2 mods, made for the Half-Life 2 leak and released in September 2004, before Half-Life 2.
Thinking with Time Machine
Thinking with Time Machine is a Portal 2 modification that introduces new time-based mechanics in addition to the standard Portal Gun.
Transmissions: Element 120
A standalone, single-player Source engine mod with a focus on physics puzzles, featuring a modified Gravity Gun known as the Zero-Point Energy Projector.
Weekday Warrior is a single-player mod for Half-Life 2. Set inside a modern corporate office environment, the player takes on the persona of Doug Smith, a very bored man with the untapped potential for greatness.
Zombie Master is a multiplayer Half-Life 2 modification centered around a zombie-apocalypse which throws all but one player in the shoes of human survivors.
Zombie Panic! Source
Zombie Panic! Source is a multiplayer Half-Life 2 modification that pays homage to the popular zombie genre of movies and games.
- The Valve Developer Community - official knowledge base for developers
- Mod DB - Mod database
- RunThinkShootLive - mods for both GoldSrc and Source engines, and some sneak peeks on unreleased mods
- Interlopers.net - Half-Life 2 News & Tutorials
- Half-Life 2 mods
- GameBanana - The Game Modding Community