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

If you want a true zero-knowledge architecture , your files must be encrypted client-side using keys derived from your password/passphrase before they are transmitted, meaning the provider has zero technical capability to read your data or recover your password.blog.mega.io+1

Because of this, if you forget your password, the provider cannot reset it or recover your files.blog.mega.io

Top cloud storage providers that meet this exact requirement include:

• Proton Drive - Built by the team behind Proton Mail, it uses a zero-knowledge architecture where files, filenames, and metadata are encrypted on your device using AES-256 before upload. Proton is based in Switzerland and offers a solid free tier alongside tightly integrated privacy ecosystem tools.dragbin.com+2
• Sync.com - Operates entirely on a zero-knowledge privacy model out of the box. Your data is encrypted locally before it leaves your device, and they do not have access to your master password or decryption keys.blog.mega.io+1
• MEGA - Provides client-side, end-to-end encryption across its entire platform by default. The encryption keys are derived directly from your user password, and they feature a generous free storage tier.blog.mega.io+1
• Tresorit - Designed heavily with compliance and business-grade security in mind, offering full client-side zero-knowledge encryption where no unencrypted keys or passwords ever touch their servers.shieldfive.com
• Filen - An open-source, zero-knowledge cloud storage provider based in Germany that handles end-to-end client-side encryption for all uploaded files.mdanassaif.medium.com+1

Alternatively, if you want to keep using a standard cloud provider (like Google Drive, OneDrive, or Dropbox) but want client-side zero-knowledge encryption, you can use a tool like Cryptomator to encrypt your files locally into an encrypted vault before syncing them to the cloud.mdanassaif.medium.com+1

To help narrow down the best fit, tell me:

• How much storage space do you need?
• Do you require real-time document editing/collaboration , or is this strictly for backup and file storage?

Yes. Look for zero-knowledge / end-to-end encrypted cloud storage.

• Proton Drive — files are encrypted client-side; Proton says it cannot access your files.Proton+1
• Tresorit — client-side encryption with keys kept under your control.Tresorit
• Cryptomator + any cloud provider — encrypts files and filenames before upload; the cloud provider never receives the vault password.docs.cryptomator.org+1

For straightforward personal use, Proton Drive is a strong fit. If you want maximum provider independence, Cryptomator lets you choose essentially any cloud backend.

One important consequence: if you lose the encryption password/key, the provider generally cannot recover your files for you.cryptomator.org

Several dedicated zero-knowledge cloud providers and local encryption tools encrypt your files client-side using end-to-end encryption so the service provider never sees your password or unencrypted data.blog.mega.io+1

Provider / Tool	Encryption Type	Free Tier	Key Advantage
Filen	Client-side zero-knowledge (E2EE)	10 GB	Open-source client code, zero-knowledge by default.
Proton Drive	End-to-end client-side encryption	5 GB	Swiss jurisdiction, integrated with ecosystem.
Tresorit	Zero-knowledge client-side encryption	None	Enterprise-grade security and collaboration.
Cryptomator	Client-side layer over existing clouds	Free (Desktop)	Works on top of Google Drive, Dropbox, or OneDrive.

Top Native Zero-Knowledge Providers

• Filen : Fully client-side encrypted cloud service based in Germany with open-source client apps. Your keys never leave your device.
• Proton Drive : Offers end-to-end encryption for all stored files and documents, backed by strict Swiss privacy laws.
• Tresorit : Focuses heavily on secure sharing and enterprise compliance using zero-knowledge architecture.
• Sync.com : Employs zero-knowledge encryption with robust folder-sync capabilities, keeping your password entirely on your local machine.blog.mega.io+1

BYO-Cloud Encryption Layer

• Cryptomator : If you want to keep using a mainstream provider like Dropbox or Google Drive, Cryptomator encrypts your files locally into a virtual vault before syncing them to the cloud. The cloud host only sees scrambled text.youtube.com+1

If you want to narrow this down, tell me:

• How much storage space do you need?
• Do you prefer a standalone service or a tool to put on top of Google Drive or Dropbox?

I can recommend the most cost-effective option for your setup.

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

A strong match: Proton Drive

Proton’s Proton Drive explicitly meets those requirements:

• Client-side encryption: files are encrypted on your device before being uploaded.Proton+1
• Provider cannot decrypt your files: Proton says it does not have access to the private keys needed to read your Drive data.Proton+1
• File and folder names are encrypted too, not just file contents.Proton
• Open-source and independently audited encryption implementation.Proton
• There is a 5 GB free plan; paid storage is available if you need more.Proton
• Importantly, if you lose your password, Proton cannot simply decrypt your files for you; recovery options need to be configured appropriately.Proton

proton.me

One distinction to watch for: "encrypted at rest" isn't enough. Services such as ordinary Google Drive, OneDrive, and Dropbox encrypt data on their servers, but that doesn't necessarily mean the provider can't decrypt it. You specifically want client-side/E2EE encryption with provider-held keys unavailable.

If you tell me roughly how much storage you need (e.g. 100 GB, 1 TB, 5 TB) and whether you need Windows/Mac syncing, I can compare the best options on those criteria.

You’re looking for zero-knowledge cloud storage (also called client-side encrypted or end-to-end encrypted storage): the provider encrypts files before upload, and the provider does not possess your password or the keys needed to decrypt your files.Cloudwards

Good options:

Provider	Why consider it	Notes
Proton Drive	Strong privacy focus, client-side encryption, integrated with Proton’s ecosystem	Good if you already use Proton Mail/VPN/etc.Cloudwards
Sync.com	One of the more mainstream zero-knowledge storage providers; encrypts stored files client-side	Good general-purpose Dropbox replacement.Cloudwards
Tresorit	Enterprise-grade security model, zero-knowledge design	Often chosen by businesses and professionals.Cloudwards
pCloud with pCloud Encryption	Offers a client-side encrypted vault option	Check that you are using the encrypted vault feature; normal pCloud storage is not the same model.pCloud
Internxt	Privacy-oriented storage with zero-knowledge claims	Worth comparing on pricing and features.Cloudwards

A few things to verify before choosing:

• Password recovery: In a true zero-knowledge system, if you lose your password (and any recovery key), the provider generally cannot restore your files because they do not have the decryption key.CloudScope
• Filename privacy: Some services encrypt file contents but leave filenames or metadata visible. Check the provider’s exact design.
• Open-source/audits: Prefer providers that publish security details, undergo audits, or make their encryption design reviewable.
• Sharing: Encrypted sharing can be tricky; make sure the provider supports the workflows you need.

If you want the closest “Dropbox, but the company cannot read my files” experience, I’d start by comparing Sync.com, Proton Drive, and Tresorit.Cloudwards

If you tell me your priorities (free tier, cheapest, maximum privacy, business use, Linux support, self-hosting, or large backups), I can narrow it down.

You are looking for a zero-knowledge, end-to-end (E2EE) encrypted cloud storage provider . With these services, files and their encryption keys are derived from your master password locally on your device before uploading. The provider only ever sees scrambled ciphertext and has no backdoor or way to recover your password if you lose it.bestbackupreviews.com+1

Top-tier providers matching this exact requirement include:

• Proton Drive: Features zero-knowledge, end-to-end encryption for your files, file names, and metadata. Based in Switzerland, it operates under strict privacy laws and doesn't know or store your master password.
• Sync.com: A privacy-first cloud storage provider based in Canada that utilizes zero-knowledge client-side encryption by default on all plans. They do not have access to your password or keys.youtube.com+2
• Tresorit: An ultra-secure, zero-knowledge cloud collaboration and storage platform designed with client-side encryption baked into its foundation. Not even their administrators can read your data.
• NordLocker: Focuses heavily on local and cloud "lockers" utilizing AES-256 and XChaCha20-Poly1305 client-side encryption. Your vault keys stay on your machine.
• Internxt: An open-source, zero-knowledge cloud storage provider that encrypts data client-side using AES-256 before it leaves your device.

Note: If you use a mainstream provider like Google Drive, Dropbox, or OneDrive, you can achieve true zero-knowledge client-side encryption by pairing them with a zero-knowledge local encryption tool like Cryptomator before syncing files to the cloud.

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

• How much storage space do you need?
• Do you need real-time collaboration/editing or just backup and sync?
• What operating systems (Windows, Mac, Linux, mobile) must it support?

Sync.com, Proton Drive, and Filen are top cloud storage providers that use a zero-knowledge architecture, meaning they encrypt files client-side and do not know your password.reddit.com+2

Zero-knowledge (or end-to-end) encryption ensures that your data is locked on your device before it travels to the cloud. Because your password generates the decryption key locally, the provider has no technical way to read your files or recover your password if lost.cloudstorageinfo.org+2

Top Zero-Knowledge Cloud Storage Providers

• Sync.com : Based in Canada, it offers strict zero-knowledge storage with native folder syncing, file versioning, and no tracking. The company cannot access your password or data.cloudstorageinfo.org+1
• Proton Drive : Built by the creators of ProtonMail, it features end-to-end encryption for files and documents with a clean interface and strong Swiss privacy laws protecting the infrastructure.reddit.com+1
• Filen : An open-source, zero-knowledge cloud storage provider based in Germany that encrypts everything client-side using AES-256.reddit.com+1
• : Focuses heavily on end-to-end encryption, allowing you to secure files both locally on your device and in their cloud infrastructure.

If you want to narrow this down, let me know:

• How much storage space do you need?
• Do you prefer a web interface or just automated desktop/mobile syncing?

To meet your requirements—client-side encryption (zero-knowledge) where the provider mathematically cannot see your data or know your password—several top-tier cloud storage services fit the bill.

Because these are true zero-knowledge systems, if you lose your password, the provider cannot reset it or recover your files.youtube.com+1

• Proton Drive : Built by the team behind Proton Mail, it encrypts files, names, and metadata on your device using AES-256 before upload. It operates under strict Swiss privacy laws and offers a seamless privacy ecosystem.youtube.com+1
• Sync.com : Designed around a zero-knowledge architecture out of the box. Your data is encrypted locally before transmission, meaning Sync has no access to your files, passwords, or encryption keys.
• Tresorit : A Swiss/Hungarian-based cloud provider focused heavily on security. It features client-side end-to-end encryption with zero-knowledge authentication, meaning authentication and decryption keys never leave your device.
• MEGA : Offers client-side zero-knowledge encryption where keys are derived directly from your password. They provide a generous free tier, but you must keep your recovery key safe because support cannot reset your credentials.
• NordLocker : Created by the team behind NordVPN, it specializes in simple, end-to-end zero-knowledge file and vault encryption on both local devices and the cloud.

If you'd like, let me know:

• How much storage capacity you need
• Whether you need real-time document collaboration or just secure file backup
• Your preferred operating system or mobile support

I can help you pick the best option for your specific workflow.