Steam Deck and Linux
Where PoE2 build files are stored on Linux: SteamOS keeps the Windows documents folder inside the Proton prefix, so the .build file lives under compatdata. Non-SteamOS Linux paths can vary by install.
Path of Exile 2 uses Steam App ID 2694490. If the folder is not under your default Steam directory, check your other Steam library roots for steamapps/compatdata/2694490/.
PoE2 runs as a Windows game under Proton, so its documents folder lives inside a Windows-like prefix under Steam data. The important tail is Documents/My Games/Path of Exile 2/BuildPlanner.
Linux paths outside Steam Deck can vary. Treat the SteamOS path as a pattern and confirm your own Steam library and prefix location.
Confirm the folder exists, place the .build file inside it, and run the validator if the game still does not show the build.
If the path does not exist, search your Steam library for compatdata, then locate the Path of Exile 2 prefix before creating BuildPlanner.
A frequent mistake is putting the file one folder too high, such as inside Path of Exile 2 instead of the final BuildPlanner folder.
The App ID is always 2694490; only the Steam library root changes when the game is installed outside the default library.
Open your Steam library folder, then search for steamapps/compatdata. Look for a prefix that contains pfx/drive_c/users/steamuser/Documents/My Games/Path of Exile 2.
If Path of Exile 2 exists but BuildPlanner does not, create BuildPlanner there and put the .build file inside it.
Use the generator to download a tiny .build file. If the starter appears in-game, your folder path is correct and the original file likely has a schema or JSON issue.
Confirm the filename ends in .build, not .build.json or .build.txt. Hidden extensions can make a valid file look right while PoE2 ignores it.
Path of Exile 2 uses App ID 2694490, so the Proton prefix directory is steamapps/compatdata/2694490. If it is missing from the default Steam directory, check your other Steam library roots.
The pattern is the same — the Windows documents folder lives inside the Proton prefix — but your Steam library location and prefix path can vary. Treat the SteamOS path as a template, not an exact match.
That's normal. Create the BuildPlanner folder yourself inside it and place the .build file there. The game does not create the folder for you.
Confirm the extension is exactly .build, validate the JSON, and reopen the in-game planner. If a minimal starter file shows but yours doesn't, the file itself is the problem, not the path.