Proton Drive

Proton Drive is the file storage service of Proton AG, a Swiss company in Plan-les-Ouates near Geneva, which opened it to everyone with its own paid plans in September 2022. According to Proton, your files are encrypted on your own device before upload, so Proton stores content it has no key to read; the apps that do this are open source and can be inspected. In return you get fewer conveniences than ordinary cloud storage: no Linux sync app, recovery that you have to set up yourself, and 200 GB as the largest personal plan without bundled services.

Who Holds the Keys

All keys are generated on your device and reach Proton only in encrypted form, so by default Proton holds no key that opens your files. Proton describes this as end-to-end and zero-access encryption, and its marketing calls the result “zero-knowledge” storage; that description is the vendor’s own, and the audits below tested the apps for bugs rather than certifying the whole design. The cryptography is OpenPGP with Curve25519 keys. Large files are split into 4 MB chunks, and each chunk is signed, so Proton’s server cannot swap, drop or reorder parts of a file without the app noticing.

What Proton Can Still See

The file contents, file and folder names and thumbnail previews are encrypted. The rest of the metadata is not. According to the Drive privacy policy, Proton can see when each file and folder was created and modified, who has which permissions, and which username uploaded each file. It stores the size of the encrypted file, not of the original. For each sharing link it sees when the link was created, when it was last opened and how many times. Like any provider, it also sees your IP address when you connect (kept temporarily against abuse, per the privacy policy) and your payment details, which go to the payment processor Chargebee, with Proton keeping your name and the last four digits of the card.

The web app at drive.proton.me is a special case. It gets its encryption code from Proton’s servers every time the page loads, so a web user trusts that Proton serves the published code on each visit. The desktop and mobile apps are installed once and update like any other app.

Sharing

Sharing keeps the encryption in two ways. A public link carries part of its secret in a section of the address that is never sent to Proton, so Proton knows the link exists but cannot open the file. You can add your own password and an expiry date, and the recipient needs no Proton account to open, download or edit through the link. The other way is inviting someone by email. If that person is not on Proton, they have to create a free Proton account before they get access; Proton says this step keeps the files end-to-end encrypted.

Losing Your Password

Proton does not store your password and cannot reset access to your files for you. Recovery has two separate parts: getting back into the account, and decrypting the data that was in it. The 12-word recovery phrase handles both. Recovery by email or SMS only resets the password; without a separate data recovery method (a recovery file, a backup stored in your browser, or trusted contacts who confirm your request) every file uploaded before the reset stays locked. If you set up nothing and forget the password, the files cannot be recovered by anyone.

Open Source and Audits

The apps are open source: the web app’s code is on Proton’s main GitHub account, the Windows, macOS, Android and iOS apps are published under the GPL-3.0 licence, and the Drive SDK under MIT. The server code is not published, so what runs on Proton’s servers cannot be checked.

Three security audits by Securitum, a Polish security firm, are public, and Proton arranged all three itself. The first tested the web app between September and October 2021 and found five issues, two rated low severity and three informational. In 2022 Securitum tested the Android app with its API, finding two low-severity issues, and the iOS app. Proton reports that Securitum found no outstanding vulnerabilities in either mobile app. No published Drive audit covers the Windows or macOS apps, and no audit is newer than 2022. Proton also runs a public bug bounty program and maintains the open-source encryption libraries the apps use, OpenPGPjs and GopenPGP. No data breach involving Proton Drive has been reported.

Ownership and Jurisdiction

Proton AG is a Swiss company, and its primary shareholder is the non-profit Proton Foundation in Geneva; Proton states it has no venture capital investors. It discloses user data only on a binding order from Swiss authorities, and for Drive that data excludes file contents, names and thumbnails. Switzerland is not part of the Fourteen Eyes intelligence-sharing alliance. Proton says it owns its server hardware in Switzerland and Germany, but its Drive security page does not say in which of the two your files are kept.

As with most Proton apps, Drive sends anonymous usage statistics by default. Proton says they contain no personal information and are deleted after 30 days, and you can switch them off in the account’s privacy settings with the “Collect usage diagnostics” toggle.

Sync and Features

The Windows and macOS apps sync a folder automatically. Linux has no desktop app, only a command-line tool for scripts and automation. Proton sets no limit on file size, on downloads per sharing link or on the number of links.

File versioning is where the free plan and paid plans differ most. The free plan keeps up to 10 versions of each file for 7 days; paid plans keep up to 200 versions for up to 10 years, and you can change those settings. The document and spreadsheet editor built into Drive supports collaborative editing with end-to-end encryption, including live cursors. Collaborators can join through a link without a Proton account.

Price

The free plan starts at 2 GB and grows to 5 GB after a few setup tasks; its sharing links with edit rights are limited to three. Drive Plus, the Drive-only paid plan, gives 200 GB for $4.99 a month on monthly billing, or $47.88 a year ($3.99 a month) on annual billing. Proton’s list of renewal prices states that both renew at the same amounts, monthly at $4.99 and yearly at $47.88, though the checkout notes that renewal prices may change under the terms.

For personal use, more storage comes only in bundles with the rest of Proton’s paid services. Proton Unlimited gives 500 GB for $119.88 a year. Proton Duo gives 2 TB for up to two people for $179.88 a year. Proton Family gives 3 TB for up to six people for $287.88 a year. Drive Professional, a business plan, gives 1 TB per user for $95.88 per user a year, but it starts at two users. Someone who needs more than 200 GB for themselves alone has to buy one of the bundles. Paid plans come with a 30-day money-back guarantee, and there is no lifetime plan.

Pros and Cons

Our Rating

Proton Drive suits people who want files encrypted before they leave the device and who are ready to store a recovery phrase somewhere safe. Encrypted file names, link sharing that does not hand the key to Proton, and document editing with end-to-end encryption are the strongest parts. The weaker parts are the audits, which were ordered by Proton and have not been repeated since 2022, the closed server code, the lack of a personal plan above 200 GB without bundled services, and the missing Linux sync app.