Steam app 979640 · updated 12 Sep 2026, 20:29 UTC
Cepheus Protocol is an Open World RTS Military Survival Game. Play as the CERC hunting Patient 0, maintain Quarantine camps, fight dangerous mutations & Rogue Civilian Combatants . There’s nobody else coming, it’s up to you now.
720 hourly samples, with the daily peak drawn over them. Weekends are shaded.
77 months, May 2020 to September 2026. The highest number of people in the game at once, each month, on a time axis -- a gap in the record stays a gap.
The highest number of people in the game at once, each month. Four, because four is as far back as the source keeps anything finer than one figure a month.
31 days, each one the highest figure that day. The source keeps no hourly detail this far back. Weekends are shaded.
31 days as the curve, each the highest figure that day. Behind it, 436 hourly samples from 13 Aug, which is as far back as the source keeps every hour. Weekends are shaded.
12 days as the curve, each the highest figure that day. Behind it, 284 hourly samples. Each dip is a night. Weekends are shaded.
Cepheus Protocol was released on 15 May, 2020.
| Language | Full audio |
|---|---|
| English | ● |
| Simplified Chinese | |
| Korean | |
| German | |
| Japanese | |
| Russian | |
| Spanish - Spain | |
| Portuguese - Portugal | |
| French |
A blank audio cell means full audio was not marked in the returned language list.
Cepheus Protocol Exodus Trailer (Legacy)
Watch on Steam
Cepheus Protocol Uprising Trailer (Legacy)
Watch on Steam5 achievements in total.
50 developer announcements, Sep 2025 to Sep 2026 · times in UTC
THE BAY AREA IS COLLAPSING. The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in the…
Dark the GreatTHE BAY AREA IS COLLAPSING. The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in the…
Dark the GreatTHE BAY AREA IS COLLAPSING. The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in the field.…
Dark the GreatTHE BAY AREA IS COLLAPSING. The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in the field.…
Dark the GreatTHE BAY AREA IS COLLAPSING. The virus is loose across the peninsula. Flashpoints are erupting across the region as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in the field.…
Dark the GreatThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
Dark the GreatA New Way to Monitor the Battlefield This Saturday, during the 100th episode of CERC HQ, we will hold the world reveal of CERC Ops, a new tactical companion built specifically for Cepheus Protocol. CERC Ops connects directly to an active…
Dark the GreatThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones. CERC forces are already in the field. Embedded military reporters…
Halcyon Winds (1)The virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
CERC Emergency Broadcast SystemThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
CERC Emergency Broadcast SystemThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
CERC Emergency Broadcast SystemThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
CERC Emergency Broadcast SystemCivilian Evacuation Is Now Live On PublicCivilian Evacuation has now moved from Experimental into the default Public install of Cepheus Protocol.For the last few weeks, players have been able to test the system on Experimental while we…
CERC Emergency Broadcast SystemThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
Dark the GreatThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
Patch notesThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
Dark the GreatThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
Dark the GreatUpdate On Progress… Live on Experimental Civilian Evacuation Mechanics Progress UpdateThis month’s update is focused on two major pieces of the rebuild: Civilian Evacuation and San Francisco North. Civilian Evacuation is entering…
Dark the GreatThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded military reporters…
Dark the Great🎧 Last Time on CERC HQ…Cepheus Protocol | CERC HQ | #84Civilian evacuation is finally coming together, and it’s reshaping how every system in the game connects.Phase three kicks off with a full evacuation framework. You can now purge or…
Dark the GreatPhase 2 is coming to a close within the next 24 hours as we finish the final adjustments to the bird systems. With that work wrapping up, development is already moving forward into the next major system update. Civilian Evacuation 2.0…
Dark the GreatCERC Command DispatchThe virus is loose across the Bay Area. Flashpoints are erupting across the peninsula as entire districts fall into chaos and infected swarms push deeper into civilian zones.CERC forces are already in the field.Embedded…
Dark the GreatDeveloper Update This WeekThis week was focused on stability, balance, and finishing key systems before the next big push.Last week we laid the foundation with client side prediction for projectiles. This week we finished the remaining save…
Dark the GreatDeveloper Update This WeekSave and Load System ExpansionContinued System CoverageThis week was heavily focused on expanding Save and Load support across additional systems.Save and Load support has now been implemented…
Dark the GreatDeveloper Update This WeekSave and Load SystemThis week was overwhelmingly focused on Save and Load.A significant amount of time went into stabilizing the system, resolving reported issues from Discord and Steam, and expanding coverage…
Dark the GreatDeveloper Update This WeekSecond pass of the Pandemic Save System is now live on all branches, including the full Save and Load UI.The first pass went live last Friday through a console command. This update moves saving and loading into a…
Dark the GreatDeveloper Update This WeekWe shipped the second pass of the Pandemic Save System, which adds the Save and Load UI on Experimental.The first pass went live Friday through a console command. This pass moves it into a real UI so you can…
Dark the GreatDeveloper Update This WeekThis week was about momentum and payoff.Coming straight off the Doctrines release, we were able to get a workable first pass of Pandemic saves running within about a week. That speed is a direct result of the…
Dark the GreatPatch Notes Summary (Jan 16 → Jan 30)AI + Vehicle PathingImproved ground vehicle pathing to reduce crashes and unnecessary driving through landscape objects. They should be a lot more intentional for when they decide to kool-aid man through…
Dark the GreatAlright everyone, quick report based off Friday in terms of what’s going on.We’re releasing an early preview of some of the Doctrine changes on Experimental going into this weekend, and I highly recommend people jump in and try it out.This…
Dark the GreatThe rebuild is now the default version of Cepheus Protocol, and the first 48 hours gave us exactly what we needed: a real stress test at scale.Discord playtests help, internal testing helps, but nothing compares to thousands of players…
Patch notesThe rebuild is now the default version of Cepheus Protocol, and the first 48 hours gave us exactly what we needed: a real stress test at scale.Discord playtests help, internal testing helps, but nothing compares to thousands of players…
Dark the GreatThe rebuild is now the default version of Cepheus Protocol, and the first 48 hours gave us exactly what we needed: a real stress test at scale.Discord playtests help, internal testing helps, but nothing compares to thousands of players…
Dark the GreatTLDRThe Rebuild is now the standard installed version of Cepheus Protocol.The old version is now called Legacy, and it remains available as a Beta option.This rebuild was done to restore stability, improve performance, and modernize the…
Dark the GreatEverything in This Post Is Playable Right Now in the Private Playtesting BranchBefore diving in: everything outlined below is already live and playable if you opt into the Private Playtesting branch on Steam. No password is required.We’re…
Dark the GreatPatch Notes:Custom Game Options added to Pandemic it supports the following:Some Infected configurablesWe also added a new "presets" directory on our workshop expanding support for sharing presets. They are JSON filesjson custom game…
Dark the GreatPatch Notes:If a unit is inside a vehicle and it dies and it will land in an unnavigable space by falling it will now kill that unitImproved the damage calculation to make units being in a destroyed vehicle roll damage randomlyAll TI Walls…
Dark the GreatA few times each week, our developers host public multiplayer sessions where we jump into the chaos ourselves—testing, refining, and showcasing the true state of the game. These sessions are open for everyone to join, chat, and experience…
Dark the GreatW.I.P New Standard Infected meshes preview!Patch Notes:Various model improvements to Alcatraz islandPandemic Treasure Island Operation last Light Added (Beta) Angel and North San Francisco will be added in the coming months as we continue…
Dark the GreatPatch Notes:Radio System UI now in FAQ here!Radio System UI Supports Scrubbing (Coop working)Radio System UI Supports Play/Pause (Coop working)Radio System UI Supports Track Sync (Coop working)Radio System crash related to the host having a…
Dark the GreatPatch Notes:Added txt log system for server owners, In the install directory there is now a Activity Log for server owners to track malicious deletions of their assets if they miss it in the activity log or if their game crashes. Its…
Dark the Great📜 Patch NotesFixed a fatal crash related to the bridges being destroyedFixed a cache issue that caused localizations to fail to switchAll localizations updated. German, Spanish, Simplified Chinese, Japanese, Korean, Russian, French and…
Patch notesCurrent State of the RebuildA few times each week, our developers host public multiplayer sessions where we jump into the chaos ourselves—testing, refining, and showcasing the true state of the game. These sessions are open for everyone to…
Dark the GreatCurrent State of the RebuildA few times each week, our developers host public play sessions where we record real gameplay to showcase the genuine state of the game. It’s a fun, open venue for players and fans to join us, talk about…
Dark the GreatHow to Opt InHere’s how to opt into the Cepheus Protocol public playtest on Steam:Open Steam and go to your Library.Right-click Cepheus Protocol and select Properties.In the left panel, click on Betas.From the dropdown menu, choose…
Dark the GreatHow to Opt InHere’s how to opt into the Cepheus Protocol public playtest on Steam:Open Steam and go to your Library.Right-click Cepheus Protocol and select Properties.In the left panel, click on Betas.From the dropdown menu, choose…
Patch notesHow to Opt InHere’s how to opt into the Cepheus Protocol public playtest on Steam:Open Steam and go to your Library.Right-click Cepheus Protocol and select Properties.In the left panel, click on Betas.From the dropdown menu, choose…
Dark the Great🎧 Last Time on CERC HQ…🎙️ Episode Summary: This week’s deep dive delivers a massive progress update on the overhaul of the Pandemic mode, featuring an all-out push to bring full replayability back online. Robert and Michael walk through…
Dark the Great🎧 Last Time on CERC HQ…Episode Summary: This week’s deep-dive walks through major updates to helicopter systems and the expanding Pandemic mode. Robert, the project director, demonstrates new helicopter features like garrisoning, virtual…
CERC Emergency Broadcast SystemLast Time on CERC HQ...🎧 Protective Formations, Pandemic Systems, and the Push for Playability📝 Episode Summary: This week's CERC HQ dives deep into the latest overhaul of the helicopter AI and the foundational work on the Pandemic game…
Dark the GreatEverything Steam lists as add-on content for this game, newest first. Prices are left out on purpose: the store answers this page in one currency and it is not the reader's.
| Name | Platforms | Released |
|---|---|---|
| Cepheus Protocol - The Last Line Novella | WindowsmacOSLinux | 02 Aug 2023 |
| Cepheus Protocol - Free Vehicle Camo Post Modern Collection | Windows | 17 Jul 2023 |
| Cepheus Protocol - Support Pack Vehicle Camo Classic Wars Collection | Windows | 17 Jul 2023 |
| Cepheus Protocol - Support Pack Vehicle Camo Modern Collection | Windows | 15 Jul 2023 |
| Cepheus Protocol - Support Pack Vehicle Camo NATO Collection | Windows | 12 Jul 2023 |
| Cepheus Protocol Digital Art Book | Windows | 10 May 2022 |
| Cepheus Protocol Novelization | WindowsmacOSLinux | 26 Sep 2020 |
What Steam runs, and with what. Straight from the app configuration.
| Description | Executable | Arguments | Platform | |
|---|---|---|---|---|
| Default | CepheusProtocol.exe | windows 64 | branch legacy,legacy-premerge | |
| Launcher | CepheusLauncher.App.exe | windows 64 | ||
| Without Launcher | CepheusProtocol.exe | windows 64 | ||
| Upload Workshop Mod | CepheusProtocol\Mods\ModUploader.exe | windows 64 |
The folders Steam Cloud syncs. The root is a token Steam uses for a location on your own machine, not a path this page can know.
| Root | Folder | Files |
|---|---|---|
WinAppDataLocal | CepheusProtocol/Saved/SaveGames | *.sav and below |
gameinstall | CepheusProtocol/Saved/SaveGames | *.sav |
It runs on public data and somebody's spare time.
https://paypal.me/KintaroPalPay[email protected]0x4d559C765AA8BFe336E36d5b76024926767eD38dTJtctWU9uetJaTBoSybd1RErW7n9duTKVG