Where Does the Proton Mail Desktop App Store Data?
Where the Proton Mail desktop app keeps its Electron profile, cache and offline message index on each OS.
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The desktop app is Electron wrapping the web client. Account data lives in a Roaming profile folder, while the message search index and GPU cache live in a separate Local tree. Bridge uses different protonmail folders; do not mix the two when troubleshooting. Knowing which tree holds what saves time when backup or cleanup is due. The profile holds account state while the Local tree holds derived data that rebuilds after sync.
Offline search downloads encrypted message bodies into IndexedDB. That folder grows with mailbox size and looks like gibberish by design. Clear it from inside the app menu when space runs low or search misbehaves. Quit the app before touching either folder by hand. Deleting while it runs can leave locks and force a fresh login with a full resync.
Where Proton Mail stores this, by platform
C:\Users\[Username]\AppData\Roaming\Proton Mail
Electron profile and settings. Message index and cache live separately under Local proton_mail Persisted. Quit the app before touching either tree.
~/Library/Application Support/Proton Mail
Profile here, caches under ~/Library/Caches. The exact IndexedDB path varies by app version, so use the in-app clear control first.
~/.config/Proton Mail
Profile here, cache under ~/.cache. Follows XDG on most distros. Flatpak installs sandbox the same layout under ~/.var/app instead.
Frequently asked questions
How do I wipe Proton Mail desktop data and start fresh?
Use the in-app menu to clear application data, or quit the app and delete the Roaming profile folder. You stay logged out and the local search index rebuilds on next sync. Uninstall alone can leave the profile behind.
Where are downloaded message contents stored?
Under the Local persisted folder in an IndexedDB tree. It stays encrypted at rest and powers offline search. The file names are hashes, so manage it through the app rather than by hand.
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