Firefox Edge Browser Error Code SEC_ERROR_INADEQUATE_KEY_USAGE: How to Fix It

Easy 10-30 minutes Medium Severity Verified June 2026
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Error Code
SEC_ERROR_INADEQUATE_KEY_USAGE
Brand
Firefox Edge
Product Type
browser
Severity
Medium
DIY Difficulty
Easy
Estimated Fix Time
10-30 minutes
The SEC_ERROR_INADEQUATE_KEY_USAGE error in Firefox means the website's SSL/TLS certificate has been used in a way that violates its own declared key usage rules — for example, a certificate meant only for signing is being used for encryption instead. Firefox enforces strict certificate validation and blocks the connection to protect you from potentially misconfigured or insecure servers. In most cases this is a server-side certificate issue, but there are several browser-side steps you can take to rule out local causes.
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Tools You'll Need

How to Fix Error Code SEC_ERROR_INADEQUATE_KEY_USAGE

  1. Reload the Page and Try a Different Browser

  2. Check Your System Date and Time

  3. Clear Firefox's Certificate and SSL Cache

  4. Remove Saved Security Exceptions for the Site

  5. Disable Antivirus or Security Software SSL Scanning

    Only disable SSL scanning temporarily for testing. Re-enable it once you have identified whether it is the cause.

  6. Test in Firefox Safe Mode

  7. Update Firefox to the Latest Version

  8. Refresh (Reset) Firefox

    A Firefox refresh will remove extensions, customizations, and some stored site data. Your bookmarks, passwords, and browsing history are preserved, but back up important data first.

  9. Report the Issue to the Website Owner

    Do not add a permanent security exception for this error on sites that handle sensitive data such as banking, healthcare, or e-commerce. The certificate misconfiguration represents a real security risk.
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When to Call a Professional

If you are a website owner or administrator and this error is appearing on your own site, you need to contact your SSL certificate provider or web hosting support to reissue the certificate with correct Key Usage extensions. If you are a regular user and the error appears on a site you must access for work or business, escalate to your IT department — they may need to push a trusted root certificate through group policy or investigate a corporate proxy intercepting SSL traffic. Do not attempt to manually edit certificate trust stores unless you are an experienced IT professional.

Frequently Asked Questions

Is SEC_ERROR_INADEQUATE_KEY_USAGE a problem with my computer or the website?
In most cases, it is a problem with the website's SSL certificate. The certificate has been configured with key usage rules that do not match how the server is trying to use it. Your browser is correctly blocking the connection. However, antivirus SSL scanning or a corrupted Firefox profile can sometimes trigger this error locally, so it is worth ruling those out first.
Is it safe to click 'Add Exception' and bypass SEC_ERROR_INADEQUATE_KEY_USAGE?
It depends on the site. For a local development server, internal corporate tool, or a site you fully control and trust, adding a temporary exception may be acceptable. However, you should never bypass this error on public websites handling passwords, payment information, or personal data, because the certificate misconfiguration undermines the security of the encrypted connection.
Why does the site work fine in Chrome but not Firefox?
Firefox uses its own stricter certificate validation engine (NSS — Network Security Services), while Chrome uses the operating system's certificate library. Chrome may be more lenient about certain key usage violations, while Firefox enforces the RFC 5280 standard strictly. The certificate is still technically misconfigured — Firefox is just the browser catching the problem.
Can my antivirus cause SEC_ERROR_INADEQUATE_KEY_USAGE?
Yes. Antivirus programs that scan HTTPS traffic intercept your browser's secure connections and re-sign them with their own certificate. If the antivirus certificate is not configured with the correct key usage extensions, Firefox will block it and show this error. Try disabling your antivirus's HTTPS or SSL scanning feature temporarily to see if the error disappears.
How do website owners fix SEC_ERROR_INADEQUATE_KEY_USAGE?
Website administrators need to reissue or replace the SSL/TLS certificate. The new certificate must include the correct Key Usage extension (e.g., 'Digital Signature' and 'Key Encipherment' for RSA) and the correct Extended Key Usage extension (e.g., 'TLS Web Server Authentication'). Most certificate authorities (CAs) issue correctly configured certificates by default — the issue often arises from custom certificate generation scripts or internal CA misconfigurations. Using a free tool like SSL Labs' SSL Test will show exactly which extensions are missing or incorrect.

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