CertScope for Firefox — CertScope Project

CertScope makes the TLS certificate issuer of the current website immediately visible. It helps users identify whether a secure connection reaches the website directly or may be passing through an enterprise TLS/SSL inspection system.

The extension uses clear color-coded indicators:
- Green indicates a certificate that is not on your flagged list.
- Red indicates that the certificate issuer matches a configured flagged pattern.
- Unclassified connections can be reviewed and added to the flagged list directly from the extension popup.

CertScope supports wildcard matching, making it possible to flag certificate issuers using patterns such as inspection cert. The on-page certificate notification can be disabled, shown briefly, or kept visible. To reduce distractions, repeated notifications can be suppressed when the certificate information has not changed.

A colored padlock is also available inside the Firefox address bar for quick, at-a-glance status information.

CertScope performs its analysis locally in Firefox. It does not collect, transmit, sell, or share browsing history, certificate information, or other user data. All settings and flagged certificate patterns remain stored locally in the browser.

Please note: a green indicator means that the certificate did not match your configured flagged patterns. It should not be interpreted as a complete security assessment of the website.