How to Share Files Securely Online: The Privacy-First Guide
Email attachments, cloud storage, and messaging apps all have different security profiles. Learn how to share sensitive documents, images, and data without risk.
Sharing sensitive files — contracts, medical records, tax documents — over unprotected channels is a significant risk. Different sharing methods have very different security profiles. Here's how to share files securely without inconveniencing yourself.
Email: Convenient but Not Secure
Standard email is transmitted in plain text and stored on servers of both the sender's and recipient's providers. For truly sensitive documents:
- Password-protect the PDF before attaching (send the password via a separate channel)
- Use encrypted email (ProtonMail to ProtonMail is end-to-end encrypted)
- Zip with a password if multiple files
Cloud Storage: Depends on Provider and Configuration
- Google Drive / OneDrive / Dropbox: Encrypted in transit and at rest, but the provider has access. Setting a sharing link to "anyone with the link" is a risk if that link is forwarded.
- Better: Share with specific email addresses only, not open links. Set expiration dates on shared links.
- Best for truly sensitive files: End-to-end encrypted services like Tresorit or ProtonDrive.
Secure File Transfer Methods
- SFTP: For technical users transferring files to/from servers
- HTTPS download links: Appropriate for most professional scenarios
- Signal: End-to-end encrypted messaging with file sharing — disappearing messages add another layer
Browser-Based Tools: Local Processing = Private
When you need to process files before sharing (compress a PDF, resize an image), tools that process locally in your browser never upload the file to any server. Tools OP processes all files in your browser — your documents never leave your device. Compress with our PDF Compressor before emailing.