Best Encrypted Cloud Storage 2026: 4 Zero-Knowledge Picks

If you are shopping for the best encrypted cloud storage 2026 has on offer, the short version is: Proton Drive for most people, Filen if price is the deciding factor, and Cryptomator if you want to keep the cloud account you already have and encrypt on top of it. Tresorit is the runner-up for teams that need admin controls and compliance paperwork. Two names you will see on other lists, Sync.com and pCloud, are ones we currently steer around, for reasons covered below.

Threat models served

Encrypted cloud storage protects against a specific set of problems. Match yourself to one of these before you pay for anything, and if none of them fits, start with what a threat model is.

1. Your cloud provider itself is the adversary. You do not want Google, Apple, or a storage vendor’s staff, scripts, or subpoena responses reading your files. This is the core case for end-to-end encryption (E2EE), where files are encrypted on your device and the provider never holds a usable key. Winner: Proton Drive, which encrypts file contents and file names client-side and publishes its cryptography.
2. Someone with leverage over your account. An ex who knows your password, a stalker, or anyone who phishes their way into a mainstream cloud account gets everything in it. E2EE storage with a strong unique password and two-factor authentication narrows that to your device security. Winner: any pick on this page, paired with a password manager and TOTP or a passkey. Note what E2EE does not do: it will not save you if your laptop itself is compromised.
3. You are required to keep client or patient data confidential. Lawyers, clinicians, and accountants need access controls and certifications more than they need maximum privacy. Winner: Tresorit, which holds an ISO 27001:2022 certification audited by TÜV Rheinland and builds for business administration.

How we compared (specs, audits, and published research, not a lab)

This is a documentation-and-research comparison, not a hands-on review. The criteria: whether encryption is genuinely end-to-end, whether file names and metadata are covered, whether the client code is open source, whether an independent audit has been published, jurisdiction, and price per gigabyte.

The most useful single input is ETH Zurich’s analysis of E2EE cloud storage, presented at ACM CCS 2024 by Jonas Hofmann and Kien Tuong Truong. They examined five providers under a malicious-server threat model and concluded the ecosystem is “largely broken.” Against Sync.com and pCloud they demonstrated key-replacement attacks that break file confidentiality, plus file injection and metadata tampering. Icedrive and Seafile had integrity problems; Seafile also allowed a protocol downgrade that speeds up password brute-forcing. Tresorit came out best of the five, with the least severe findings (metadata tampering, and key replacement requiring a forged certificate). Per the researchers’ disclosure notes from October 2024, Seafile patched its downgrade issue, while Sync.com and pCloud had not responded to repeated contact attempts. That silence is why neither appears in our picks, despite their popularity. Proton Drive and Filen were not part of the study, so treat this as evidence against the five named vendors rather than a clean bill for anyone else. For ongoing breach and disclosure coverage of vendors like these, we keep an eye on techsentinel.news.

The picks

Proton Drive (best for most people). Files, folders, and their names are encrypted on your device using Curve25519 keys and the OpenPGP standard, with signatures to detect tampering. The apps and the encryption libraries (OpenPGP.js, GopenPGP) are open source, and the apps have been audited by Securitum, with reports published. Proton operates under Swiss law and is outside US and EU jurisdiction, which matters less than marketing implies but does raise the legal bar for bulk requests. The free tier gives you 5 GB, enough to try the workflow before paying. Proton’s other products are covered separately on this site: ProtonVPN vs Mullvad for the VPN side, and how to make an anonymous email account for signing up to Proton Mail without a phone number.

Filen (budget pick). A German company, servers and headquarters in Germany, offering zero-knowledge E2EE with AES-256. As of August 24, 2026, its Pro I plan is 200 GiB for €1.99 a month, the cheapest E2EE storage of comparable size we found, and plans stack on one account. Filen says all of its apps are open source; that claim is vendor-sourced, and we did not find a published third-party audit comparable to Proton’s Securitum reports.

Cryptomator (best if you keep your current cloud). Not a storage service but an open-source encryption layer: it creates a password-locked vault inside Dropbox, Google Drive, OneDrive, or any folder that syncs, encrypting file contents and file names with AES-256 before they leave your machine. Your provider keeps hosting the bytes; it just can’t read them. The desktop apps are free (donation-supported) on Windows, macOS, and Linux; the iOS and Android apps are paid. The project has undergone independent security audits and its code is public.

Tresorit (runner-up, for teams). End-to-end encryption with keys generated on your devices, a password that never leaves your device, Swiss privacy framing, and the compliance credentials (ISO 27001:2022, certified by TÜV Rheinland) that a firm’s clients will actually ask about. It is priced and packaged for business.

Pricing, as of August 24, 2026

Proton Drive: 5 GB free; Drive Plus is 200 GB with 10 years of file version history, and every paid Proton plan carries a 30-day money-back guarantee (current dollar pricing is on Proton’s pricing page). Filen: Pro I at €1.99/month for 200 GiB, up to Pro X at €39.99/month for 10 TiB, all with client-side encryption included rather than sold as an add-on. Cryptomator: free desktop, one-time-purchase mobile apps, plus whatever your existing cloud already costs you.

The catch

Every product has one. Proton Drive: the good per-gigabyte value lives in the Unlimited, Duo, and Family bundles, so Proton is quietly selling you its whole ecosystem, and 5 GB free is thin next to mainstream clouds. Filen: young company, euro-denominated pricing, and security claims that rest on vendor documentation rather than a published independent audit. Cryptomator: it is storage for you, not a sharing product; there are no encrypted share links, mobile costs extra, and you still depend on your underlying cloud account’s security for availability. Tresorit: even the best performer in the ETH Zurich study still had demonstrated metadata-tampering and certificate-forgery findings, and its pricing reflects a business product, not a personal one.

None of these encrypts your way out of a compromised device, a reused password, or a phishing page. E2EE storage solves one problem, the provider reading your files, and it solves it well when the cryptography holds. It also does nothing about the metadata inside the files themselves, so strip metadata before sharing files when the recipient matters. Pick the one that matches your threat model, turn on two-factor authentication, and put the vault password in a password manager.

Related across the network

• Are Free VPNs Safe for Privacy? What the Research Shows — privacyranker.com
• Email Security Threat Model: Who Reads Your Email? — securemailguide.com
• Embedding Inversion: Reconstructing Text From Vectors — adversarialml.dev
• Membership Inference Attacks: What Works on Production ML APIs — adversarialml.dev
• Model Inversion Attacks: Reconstructing Training Data from Output — adversarialml.dev