It still launches the current version

01Three causes

When a freshly-downgraded game runs the current version, it's one of these, in rough order of likelihood:

1. Steam quietly re-updated the install before or as you launched.
2. The game's own Steam DRM relaunched the latest build when you ran the executable directly — the SteamAPI_RestartAppIfNecessary mechanism.
3. A separate launcher (Rockstar, Paradox, Bethesda, EA) repaired the game forward before it started.

Work through them in order; the first two cover the large majority.

021 · Steam re-updated it

The most ordinary cause: between copying the old files in and launching, Steam applied an update — bringing you right back to current. Check the game isn't mid-update, then stop it happening again:

• Properties → Updates → "Only update this game when I launch it." Steam offers no true "never," so this is the first lever.
• Add the enforcement trick: set appmanifest_<appid>.acf in steamapps\ to read-only (file Properties), so Steam can't rewrite it to schedule an update. Untick it the day you want to move forward.
• Then re-copy the old build over the install (if the update already overwrote it) and launch.

If launching through the Steam UI keeps queuing an update no matter what, that's your cue to launch the executable directly instead — which surfaces cause 2.

032 · The restart DRM

Here's the sneaky one. Many games include a lightweight Steam DRM check at startup: the Steamworks call SteamAPI_RestartAppIfNecessary. When the game's executable is launched directly — not started by Steam — this call tells Steam, "hey, launch me properly," and Steam dutifully starts the installed (current) version through the library. The result looks exactly like your downgrade failing: you double-click the old game.exe, the window flashes, and the current build opens instead. Your files are fine; the game bounced you to Steam's copy. This is why simply copying an old build into place and running it often isn't enough on its own.

04The steam_appid.txt fix

The fix is one small text file. Placing a file named steam_appid.txt containing just the game's App ID next to the executable tells the Steamworks SDK "Steam already knows about me" — so it skips the restart check and the exe runs as-is, on your old build.

1. In the downloaded build's folder, next to the game's .exe, create a plain text file named exactly steam_appid.txt.
2. Put just the App ID inside it — one line, the number, nothing else (e.g. 550 for Left 4 Dead 2). No quotes, no extension beyond .txt.
3. Keep Steam running and logged in (the game still wants Steam for ownership and friends), and launch the .exe directly — not through the Steam library.

This is the trick the PAYDAY 2, Left 4 Dead 2 and Risk of Rain 2 guides all use, and it's the standard way to run a downgraded Steam game standalone. A bonus: a build launched this way is invisible to Steam's updater, so it can't be dragged forward — which makes side-by-side versions (an old folder beside your current install) reliable.

053 · A separate launcher

Some games don't boot straight into the game — they go through the publisher's own launcher (Rockstar Games Launcher, the Paradox launcher, Bethesda's, EA's), and that launcher often "repairs" or updates an old build forward before it runs. The fix is game-specific, because each launcher has its own escape hatch:

• Rockstar (GTA V): the offline Social Club flag (-scOfflineOnly) stops the launcher phoning home about versions — see the GTA V guide.
• Paradox / Bethesda / others: an offline mode or a no-update argument; the relevant per-game guide covers it.
• The branch-switch that didn't take: a cousin of this — if you used Steam's Betas tab and it didn't downgrade, check whether a DLC requires the current build and is silently keeping you on it (the Factorio Space Age case is the classic). Untick the DLC, then pick the branch.

06The surest setup

If you want a downgraded version that cannot be undone by Steam, the most bulletproof route avoids the whole problem — and it's the one I'd recommend every time: keep the old build in its own folder, away from your Steam install, with a steam_appid.txt, and launch it from there (or add it as a non-Steam game). Steam never updates a folder it doesn't manage, the restart DRM is satisfied by the appid file, and your current install stays current and separate. The full walkthrough of installing and running a downloaded build — including this standalone route — is in after the download; this page is just the "why is it still the new version" half of it.