I need a cloud storage provider that encrypts files client-side and does not know my password.

You are looking for zero-knowledge, end-to-end encrypted (E2EE) cloud storage. With these providers, your files are encrypted and decrypted on your local device using keys derived from your password, meaning the provider only ever sees scrambled ciphertext and has no technical way to read your files or recover your password if you lose it.

Top-tier cloud storage providers utilizing true client-side zero-knowledge architecture include:

• Proton Drive : Built by the team behind ProtonMail, Proton Drive uses strict open-source, audited zero-knowledge encryption . Your files are encrypted on your device before upload , protected under Swiss privacy laws , and the company cannot access your keys.
• Tresorit : A heavily secure, business-grade cloud storage option based in Europe. Tresorit applies client-side zero-knowledge encryption across all platforms (including web access), and unencrypted data or keys never touch their servers.
• Sync.com : Based in Canada and compliant with strict privacy regulations, Sync.com features native zero-knowledge architecture built into every account , ensuring only you have the keys to your data.
• pCloud (with pCloud Crypto) : While standard pCloud storage doesn't default to zero-knowledge, you can add pCloud Crypto , which creates a dedicated client-side encrypted folder ("Crypto Folder") where files are locked before leaving your device.
• NordLocker : Developed by the creators of NordVPN, NordLocker is built entirely around a zero-knowledge cloud and local file-encryption model where your master password controls the keys.

Note: Because these are true zero-knowledge services, if you lose your password, the provider cannot reset it or recover your data for you. Be sure to safely store your account recovery phrase or master password.

If you'd like to narrow this down, let me know:

• How much storage capacity do you need?
• Do you prefer a monthly/annual subscription or a one-time/lifetime payment model?
• What operating systems/devices will you be syncing from?

You’re looking for zero-knowledge cloud storage (also called client-side encrypted, end-to-end encrypted, or privacy-first storage): the provider encrypts files on your device, and the provider never has your password or the decryption keys needed to read your files.

Good options:

Things to verify before trusting any provider:

• “Zero-knowledge” should mean the provider cannot decrypt your files.
• Your password should never be sent to the server as the encryption key.
• File names and metadata matter: some services encrypt file contents but leave filenames or folder structures visible.
• Account recovery is a trade-off: if the company truly does not have your keys, they usually cannot restore your data if you lose your password/recovery key.

My shortlist:

• Best overall for most people: Proton Drive
• Best for business/security-heavy use: Tresorit
• Best Dropbox replacement: Sync.com
• Best if you want open-source transparency: Filen or Koofr Vault

If you want the strongest possible setup, another route is encrypting files yourself before uploading (for example with a local encrypted vault) and then using any cloud provider only as storage. That gives you more control but is less convenient.

If you want a provider that performs client-side (zero-knowledge) encryption—meaning your data is scrambled on your device before it ever touches their servers and they have no way of knowing your password or recovery key—you have a few top-tier options.

The best options fall into two categories: dedicated zero-knowledge cloud storage providers and a client-side encryption tool you can use with any mainstream cloud.

Dedicated Zero-Knowledge Cloud Providers

1. • MEGA Cloud : Offers zero-knowledge, client-side encryption by default across all files and chats. Keys are derived directly from your password on your device. If you lose your password, MEGA cannot reset it for you, meaning they truly do not know or store it. They also provide a generous free tier (20 GB).
2. • Tresorit : Built from the ground up for zero-knowledge security and business compliance. Client-side encryption happens using AES-256, and your password/keys never leave your device. It's more expensive than consumer storage, but heavily optimized for privacy.
3. • Sync.com : Provides strict zero-knowledge, end-to-end encryption. Like MEGA, your password is used to generate the master cryptographic keys locally, meaning they have zero technical ability to access or view your files or reset your password for you.
4. • pCloud : While standard pCloud folders are server-side encrypted, they offer an add-on called pCloud Crypto . This creates a dedicated client-side encrypted "Crypto folder" where files are locked with a passphase only you know. pCloud explicitly states they have zero-knowledge of this key.

The Bring-Your-Own-Cloud Alternative (Free & Open Source)

• Cryptomator : If you already use Google Drive, Dropbox, OneDrive, or iCloud but don't trust them with your data, you can use Cryptomator. It is a free, open-source tool that creates a client-side encrypted "vault" inside your existing cloud folder. It uses AES-256 encryption for both files and filenames, runs entirely on your hardware, and the cloud provider only sees scrambled gibberish. Because it is entirely local, no cloud company or third party ever sees your password.

To help narrow down the right pick, tell me:

• How much storage space do you need?
• Do you prefer an all-in-one cloud service (like MEGA or Sync) or do you want to encrypt files on top of an existing provider (like Google Drive/Dropbox using Cryptomator)?

Yes. What you want is generally called zero-knowledge / end-to-end encrypted (E2EE) cloud storage: encryption happens on your device, and the provider does not possess the key needed to decrypt your files.

My top pick: Proton Drive

Proton’s Proton Drive is a particularly good fit:

• Client-side encryption: files are encrypted on your device before being uploaded.
• Provider can't decrypt your files: Proton says it doesn't have access to your private encryption key.
• Filenames and folder names are also encrypted, not just file contents.
• Open-source and independently audited encryption implementation.
• There is a free 5 GB tier, with larger paid plans available.
• Importantly, forgetting your password can mean losing access to your data unless you've configured recovery. Proton explicitly says it cannot simply recover your encrypted files for you.

One important distinction

If by "does not know my password" you mean the provider should never possess either your password or the ability to decrypt your files, Proton Drive fits very well.

If you want an even more conservative setup, you can also use a conventional cloud provider (Google Drive, Dropbox, OneDrive, etc.) with client-side encryption software such as Cryptomator. In that arrangement, the cloud provider receives only encrypted files, and the encryption password/key never leaves your computer. The tradeoff is more setup and less seamless searching/previewing.

For most people, I'd choose Proton Drive if you want the convenience of normal cloud storage while retaining zero-access encryption.

Yes. What you want is usually called zero-knowledge, end-to-end encrypted (E2EE) cloud storage: files are encrypted on your device before upload, and the provider doesn't possess the keys needed to decrypt them.

My top picks

• proton.me — best overall for most people. Files are encrypted client-side, and Proton says it cannot decrypt your files. It also encrypts filenames and folder names. There is a free tier with 5 GB.
• tresorit.com — best for maximum security/business use. Tresorit explicitly uses zero-knowledge E2EE, with encryption keys generated/managed on your device. It says your password never leaves your device. Its free Basic plan currently offers 3 GB.
• sync.com — good balance of privacy and conventional cloud-storage features. Sync advertises E2EE and zero-knowledge authentication and says it cannot see your files.

One important distinction

If by “does not know my password” you mean the provider literally never receives your password or a usable copy of it, Tresorit is particularly explicit about this: its zero-knowledge authentication keeps your password on your device.

With any zero-knowledge service, though, losing your credentials can mean losing access to your encrypted data. That's the tradeoff: the provider can't decrypt your files for you either.

My recommendation: start with Proton Drive if you want something simple and affordable; choose Tresorit if security/privacy is the overriding priority. If you tell me how much storage you need (e.g. 100 GB, 1 TB, 5 TB), I can compare the current prices and features.

You are looking for zero-knowledge, client-side encrypted cloud storage . With this architecture, files are encrypted and decrypted strictly on your device, meaning the provider never sees your plaintext data, doesn't store your master password, and cannot hand over readable files even if compelled by a legal subpoena.

The top dedicated cloud providers meeting this exact criteria, plus a DIY alternative, include:

1. Proton Drive : Features open-source, audited, end-to-end encryption on all plans by default. It operates out of Switzerland with a strict zero-knowledge framework, meaning Proton has no technical ability to read your files or recover your password.
2. Sync.com : A privacy-focused service providing zero-knowledge client-side encryption on all accounts. It offers robust file-sharing controls and history tracking while ensuring that your password and keys never touch their servers.
3. Tresorit : Built with a heavy security-first focus, offering automated client-side zero-knowledge encryption and compliance certifications. Headquartered in Switzerland, it prevents any server-side visibility into your data.
4. NordLocker : Employs client-side zero-knowledge architecture using advanced algorithms (AES-256, xChaCha20). Your encryption keys are derived from your master password locally, keeping your files private even during a data breach.
5. MEGA : Applies client-side end-to-end encryption by default to all stored and shared files. Keys are derived directly from your password, and the provider has no administrative override or visibility into the contents.
6. Cryptomator : If you prefer using a mainstream provider like Google Drive, Dropbox, or OneDrive, Cryptomator is a free, open-source tool that encrypts your files client-side before they sync to the cloud. You supply the password locally, and the cloud provider only sees unreadable ciphertext.

Note on zero-knowledge design: Because these systems do not know or store your password, if you lose your password or recovery key, the provider cannot reset it or recover your data.

Would you prefer a native cloud provider (like Proton or Sync) or a client-side encryption tool (like Cryptomator) that works with an account you already have? Also, let me know your storage capacity needs so I can narrow down pricing.

What you are looking for is a zero-knowledge, end-to-end (E2EE) encrypted cloud storage provider . With these services, your files are encrypted and decrypted locally on your device using keys derived from your password. The provider only ever sees unreadable ciphertext, meaning they cannot read your files and cannot recover your password if you lose it.

The top cloud storage providers that provide zero-knowledge client-side encryption by default include:

• Proton Drive — Built by the privacy-focused team behind Proton Mail, offering zero-knowledge encryption by default, open-source client apps, and strong Swiss privacy laws.
• Tresorit — An enterprise-grade, highly polished secure sync service based in Switzerland that applies zero-knowledge protection to all files by default (though it lacks a free tier).
• MEGA — Features zero-knowledge end-to-end encryption for all files by default and stands out for offering a generous free storage tier.
• Filen — A zero-knowledge, open-source, and privacy-oriented cloud storage provider based in Germany that shards data across independent nodes.
• Internxt — Uses client-side zero-knowledge encryption combined with post-quantum cryptography and fully open-source apps.

Note: Providers like pCloud and IceDrive offer zero-knowledge, but it is either restricted to a specific paid add-on folder or requires manual activation rather than applying comprehensively by default. Another alternative is using standard cloud storage (like Google Drive or Dropbox) alongside standalone client-side encryption tools like Cryptomator.

To help narrow down the best fit, tell me:

• How much storage space do you need?
• Do you need collaboration/file sharing , or is this strictly for personal backup?

You’re looking for a zero-knowledge (or client-side end-to-end encrypted) cloud storage provider. The key properties to look for are:

• Files are encrypted before upload on your device.
• The provider stores only ciphertext.
• Your password is never sent to the provider and cannot be used by them to decrypt your files.
• If you lose your password/recovery key, the provider cannot recover your data.

Good options:

A few things to verify before trusting a provider:

1. “Encrypted at rest” is not enough. Google Drive, Dropbox, and OneDrive encrypt stored data, but they generally hold the keys needed to access it.
2. Look for wording like “zero knowledge,” “client-side encryption,” “end-to-end encryption,” and “we cannot recover your password.”
3. Check whether filenames and metadata are encrypted too; some services only encrypt file contents.
4. Prefer providers with published security documentation, audits, or open-source clients where possible.

For most individuals:

• Easiest privacy-first choice: Proton Drive or Sync.com
• Highest security/business focus: Tresorit
• Maximum control: Cryptomator + your preferred cloud storage
• Need lots of storage: pCloud Crypto or MEGA

One important tradeoff: a true zero-knowledge provider cannot reset your password and restore your encrypted files. Keep a recovery key or password-manager backup somewhere safe.

What you are looking for is a zero-knowledge, client-side encrypted cloud storage provider . With these services, your files are encrypted and decrypted locally on your device using a key derived from your password. The provider only ever sees scrambled ciphertext, meaning if you lose your password, they cannot recover or reset it for you.

Top cloud storage providers that operate on a zero-knowledge architecture by default include:

• Sync.com : Highly reliable for business and personal use, features continuous file syncing, and applies zero-knowledge privacy controls to all files by default.
• Proton Drive : Offers open-source client apps, end-to-end encryption, and strong Swiss privacy laws safeguarding your data.
• Tresorit : Premium, enterprise-grade cloud storage with zero-knowledge encryption and rigorous compliance audits.
• Filen : A lightweight, open-source, zero-knowledge cloud provider focused heavily on privacy and zero-knowledge redundancy.
• Internxt : Open-source, zero-knowledge file storage that utilizes file-sharding for extra distribution security.
• MEGA : Provides client-side encryption by default across all plans and offers a generous free storage tier.

Alternatively, you can use Cryptomator , a free and open-source tool that encrypts files client-side into a local folder, which you can then sync to any standard cloud provider (like Google Drive, OneDrive, or Dropbox) without the provider ever seeing your password or readable files.

If you'd like, let me know:

• How much storage capacity you need
• Whether you prefer a free tier or a paid subscription
• Your primary operating systems (Windows, Mac, Linux, Mobile)

I can help you narrow down the best specific provider for your setup.

Yes. What you’re looking for is usually called zero-knowledge or client-side end-to-end encryption (E2EE): your files are encrypted before upload, and the provider does not possess the key needed to decrypt them.

My top picks

1. Proton Drive — my recommendation for most people.
Proton says files are encrypted end-to-end before leaving your device and that even Proton cannot access your files. Its free plan currently includes 5 GB.

2. Tresorit — strongest fit if security is the priority.
Tresorit explicitly says files are encrypted on your device, encryption keys aren't stored in readable form by Tresorit, and your password never leaves your device. Importantly, if you lose your password and aren't signed in anywhere, Tresorit cannot recover your data.

3. MEGA — good if you want more free storage.
MEGA uses client-side encryption and derives encryption keys from your credentials. Its free allowance is substantially larger than Proton's.

One important distinction

Don't just look for a provider advertising "AES-256 encryption" or "encryption at rest." Google Drive, Dropbox, etc. encrypt data, but the provider generally controls the encryption keys.

You specifically want:

Your device → encrypts file → encrypted file uploaded → provider stores ciphertext → your device decrypts it

rather than:

Your device → uploads file → provider encrypts it → provider holds the keys

If you tell me how much storage you need (e.g. 500 GB, 2 TB, 10 TB) and whether you need automatic desktop/iPhone/Android syncing, I can narrow this to the best 2–3 choices and compare their current pricing.