Tresorit

Tresorit is a cloud storage service from Zurich that encrypts files on your device before they are uploaded. It was founded in 2011, aims its products mainly at organizations, and has been owned by Swiss Post since 2021. Plans for individuals are called SecureCloud for Private Use: a free plan with 3 GB and three paid plans with 50 GB, 1 TB and 4 TB.

Tresorit describes its service as zero-knowledge, meaning it cannot read your files. An EY review commissioned by Tresorit found that claim well founded. An independent study by ETH Zurich cryptographers found two weaknesses: a compromised server could hand you a fake key and read the folders you share afterwards, and it could change some file details. Tresorit also sees the names of top-level folders, who has access to them, and the size of each file. The apps and the server are closed source.

Encryption & Key Custody

Tresorit says it encrypts every file on your device with its own randomly generated key and never receives those keys in readable form. This puts key custody with you: the provider stores data it cannot decrypt. Your password does not leave the device either; the apps prove they know it with a challenge-response check instead of sending it to the server.

The metadata encryption covers file names and subfolder names, each with its own key. It does not cover everything. Tresorit’s privacy policy says that the names of top-level folders, which Tresorit calls tresors, their size and their member list are not encrypted. The ETH Zurich study found that some file metadata is also readable and can be changed by the server: file size, file type, creation time and who created a file.

Sharing works in two ways. A shared folder gives another Tresorit user its keys, encrypted with that person’s public key. A link puts a random secret into the link itself, so the recipient can decrypt the file without an account; you can add a password, an expiry date and a download limit (on Personal Lite, links expire after 30 days and the expiry cannot be changed). Links carry up to 2 GB, or 5 GB on Personal Pro.

The public keys of the people you share with are vouched for by a certificate authority that Tresorit runs itself. The ETH Zurich researchers pointed out that an attacker who took over Tresorit’s servers and could get certificates signed could hand you a fake key and read the folders you share afterwards. They did not carry out this attack against the live service. Files you never share are not exposed this way.

Account recovery is the price of this model. Tresorit does not store your password, so if you forget it and are not signed in on any device, the only option is to reset the account, which deletes every file stored in it. If you are still signed in somewhere, you can set a new password with a code sent by email. Keep the password in a password manager and keep a copy of important files elsewhere.

Web Access, the browser version, decrypts your files inside the browser. The code that does this is loaded from Tresorit’s servers every time you open the page, so in the browser you depend on Tresorit serving unaltered code; the desktop and mobile apps do not have this exposure on each visit.

Trust & Transparency

The Tresorit apps and server are closed source, so outside reviewers can examine the code only by arrangement with Tresorit, and readers cannot check it themselves. The ETH Zurich researchers named the lack of open-source code and of a formal security analysis as obstacles to outside review.

Three outside reviews are public. In 2019 the EY Advanced Security Center ran penetration tests, a source code review and a cryptographic review of the encryption and the apps; Tresorit commissioned this security audit, and EY concluded that Tresorit’s servers and staff never receive readable data or keys. At the end of 2025 an auditor that Tresorit does not name ran a penetration test, also commissioned by Tresorit, and found no high or critical issues, one medium-severity bug on the server side and a few other medium and low issues. Neither full report is public.

The third review was independent: a 2024 study by cryptographers at ETH Zurich, presented at the ACM CCS conference, tested five encrypted storage services against a server controlled by an attacker. It found the fake-key and metadata weaknesses described above in Tresorit; the fake-key attack would expose every folder shared after the swap. The other four services tested had more severe flaws, and Tresorit’s blog quotes the researchers calling its design “mostly unaffected” by their attacks. The researchers’ site records that Tresorit acknowledged their message in September 2024 and does not say whether either weakness was changed.

Tresorit AG is registered in Zurich and its terms are governed by Swiss law. Files of personal accounts outside Switzerland are stored on Microsoft Azure in Ireland, and account metadata is always kept in Ireland. Tresorit says it answers only Swiss authorities, so a foreign request needs a decision by a Swiss authority first, and that it can hand over account data and metadata but not file content. Its transparency report covering January 2019 to November 2021 describes these rules.

Whatever the encryption, Tresorit sees your name and email address, payment details, IP addresses, the device and app version you use, when you sign in, how much you store, and the folder information described above. The privacy policy lets you switch off usage statistics in the app settings, which makes the telemetry opt-out. There is no known data breach of Tresorit.

Swiss Post bought a majority stake in Tresorit in July 2021. Both companies say Tresorit continues as an independent company within the Swiss Post group, and its offices are in Switzerland, Germany and Hungary.

Features & Sync

The desktop sync apps run on Windows, macOS and Linux and keep chosen folders in step with the cloud. Tresorit Drive adds the cloud to your file manager as a drive, so you can open files without keeping a local copy. The mobile apps upload camera photos automatically, and Personal Essential and Personal Pro add a document scanner in the app.

File versioning is limited by count and depends on the plan: Personal Lite (50 GB) keeps 5 previous versions of each file, Personal Essential (1 TB) 10 and Personal Pro (4 TB) 25. An earlier version can be downloaded, but not set back as the current file; you upload it again instead. Deleted files and subfolders go to a trash folder and can be restored, but a deleted top-level folder cannot.

Personal Pro adds file requests, which let people without an account upload files to you, and access logs that show who opened your links, from which IP address and when. Files are capped at 2 GB on Personal Lite and 10 GB on the other paid plans.

Web Access can open and edit Word, Excel and PowerPoint files in the browser, but it has no real-time collaborative editing: when two people edit the same file, each person’s changes are saved as a separate version.

Usability & Platforms

There are apps for Windows, macOS, Linux, Android and iPhone, plus Web Access in the browser, on every plan. Personal Lite syncs two devices; Personal Essential and Personal Pro sync ten. Two-factor authentication is available on all plans, with codes by text message, email, phone call or an authenticator app, and support answers by email and chat. A forgotten password can be changed only from a device that is still signed in.

Price & Value

The free plan, called Basic, gives 3 GB, files up to 500 MB and sync on two devices, with no card required. Tresorit may close a free account after 210 days of inactivity.

Paid plans, billed yearly: Personal Lite costs $57 a year for 50 GB, Personal Essential $143.88 a year for 1 TB, and Personal Pro $329.88 a year for 4 TB. Paying monthly costs $5.99 a month for 50 GB, $13.99 for 1 TB and $33.99 for 4 TB. A 14-day trial is available on each plan but asks for payment details. A plan bought directly can be refunded in full within 7 days, or 14 days in the EU; a subscription that started as a trial cannot.

Pros and Cons

Our Rating