NOTE: ProtonMail may use different SSL/TLS certificates for our subdomains. The information below pertains only to our main site protonmail.com.
ProtonMail is all about privacy, and we want to do our best to protect everyone’s data and communication. When accessing protonmail.com, the transmission of information between your browser and our servers in Switzerland is always encrypted and protected by HTTPS. While this is not the same as the end-to-end encryption concept of PGP, it is nevertheless important for protecting you from man-in-the-middle attacks and other forms of communication eavesdropping.
For HTTPS to work, each website must have an SSL/TLS certificate that is verified by a trusted certificate authority. The certificate authority that vouches for ProtonMail is SwissSign AG. A modern browser should automatically check the validity of the certificate of an HTTPS-protected website and alert you if it detects something untrustworthy. For the uber-security-conscious users who want to check manually, the fingerprints of our certificate are:
If this matches what you see in your browser, then you know you are communicating with the real ProtonMail website and using the correct public key to encrypt your sensitive information, and only ProtonMail can decrypt it.
To check the thumbprint in Chrome:
- Click on the menu (⋮) displayed on the top right corner after the browser address bar.
- Click More tools > Developer Tools.
- Select the Security tab. Click on View Certificate and go to Details. You will find the certificate details with fingerprints at the bottom.
In Details, show All and verify the Thumbprint matches the one above (make sure you are looking at the certificate for protonmail.com, not SwissSign AG).
To check the fingerprint in Firefox:
Click on the lock button in front of the URL and click on More Information.
Go to Security and click on View Certificate.
To check the fingerprint in Safari:
Click on the Green Bar stating: “Proton Technologies AG”.
Select Show Certificate. In Details, scroll to the bottom of the page to see the SHA1 Fingerprint.
We will continue to improve our security protocols and roll out more security features as we scale up. Thanks for all the interest and help from the community!