Mozilla Observatory Alternative: The Best Replacements in 2026
For almost a decade, Observatory by Mozilla was the default free answer to the question "how secure is my website's configuration?". Then it was retired. The HTTP scanning half found a new home on MDN in July 2024, while the rest of the toolkit, including the TLS Observatory and the SSH Observatory, was shut down for good in September 2024, as documented in MDN's launch announcement.
If you still have observatory.mozilla.org bookmarked, or your security checklist references tests that no longer exist, you need a replacement. This guide compares the best Mozilla Observatory alternatives in 2026, explains exactly what each one covers, and shows how to rebuild your old scanning workflow without losing coverage.
What happened to Mozilla Observatory?
Observatory started in 2016 as an internal Mozilla tool, built by security engineer April King to push Mozilla's own websites toward modern security practices. Once opened to the public it became a fixture of the web security community: by the time of the migration it had scanned 6.9 million websites across 47 million scans, according to MDN.
| Date | Event |
|---|---|
| 2016 | Observatory by Mozilla launches publicly |
| 2016 to 2024 | 6.9 million websites scanned, 47 million total scans |
| July 2, 2024 | HTTP Observatory relaunches on MDN with an updated test suite |
| September 2024 | observatory.mozilla.org is sunset; the TLS and SSH Observatories retire with it |
The migration was not a simple rebrand. The MDN team modernized the tests:
- The outdated X-XSS-Protection test was removed.
- Legacy Flash and Silverlight cross-domain policy tests were removed.
- A new Cross-Origin-Resource-Policy (CORP) test was added.
- Referrer-Policy scoring was updated.
- Scans are now rate-limited to one per site every 60 seconds.
One change matters more than all the others: the new MDN HTTP Observatory analyzes HTTP response security only. Mozilla states there are no plans to bring back the TLS and certificate analysis tabs. If your old routine was "run Observatory, fix the headers, then check the TLS tab", the second half of that workflow now needs a different tool.
What to look for in a replacement
Three questions separate the candidates quickly:
- Coverage. Headers are one layer. A realistic external audit also covers TLS configuration and certificate expiry, DNS records, email authentication (SPF, DKIM, DMARC), and ideally whether your credentials already circulate on the dark web.
- Actionability. A letter grade is motivating, but the report should tell you which header to change and what value to set, not just that something failed. Observatory's gamified hunt for the A+ worked precisely because it paired grades with documentation.
- Workflow fit. Rate limits, scan speed, whether you can monitor continuously or only scan manually, and price.
With those criteria in mind, here are the tools worth your time in 2026.
The best Mozilla Observatory alternatives in 2026
1. FortifyNet: the closest thing to a full Observatory successor
FortifyNet runs a free scan in about 60 seconds and covers the six areas most external audits care about: security headers, SSL/TLS configuration and certificate expiry, DNS health, email authentication (SPF, DKIM and DMARC), dark web exposure of your domain's credentials, and performance basics. Results come back as a graded report with concrete fixes written in plain language.
That breadth is the point. The old Mozilla Observatory bundled HTTP and TLS testing in one place; FortifyNet restores that single-dashboard experience and extends it to email authentication and breach exposure, which Mozilla never covered. The scan itself is free with no signup, while continuous monitoring and alerting sit in the paid plans, so the model is freemium rather than purely free.
Best for: teams that want the whole external security picture in one scan.
Limitations: it is a breadth-first audit, not a deep penetration test.
2. MDN HTTP Observatory: the official successor
The MDN HTTP Observatory is the direct descendant and remains excellent at its narrower job. It runs roughly ten tests against your HTTP responses: Content-Security-Policy, cookie configuration, CORS, Strict-Transport-Security, redirection behavior, Referrer-Policy, Subresource Integrity, X-Content-Type-Options, clickjacking protection via frame-ancestors and X-Frame-Options, and CORP. Every failed test links straight into MDN's security guides, which are among the best free documentation on the subject, and historic scan data from the old Observatory was preserved.
Best for: deep, well-documented header and policy analysis.
Limitations: no TLS, certificate, DNS or email checks; one scan per minute per site.
3. securityheaders.com: the fastest header grade
Scott Helme's securityheaders.com, which now operates under Snyk, is the quickest way to get an A+ to F grade on your response headers, and it had already passed 250 million scans in 2023. It checks the presence and sanity of the headers that matter most: Content-Security-Policy, Strict-Transport-Security, X-Frame-Options, X-Content-Type-Options, Referrer-Policy and Permissions-Policy.
Best for: instant spot checks and shareable grades.
Limitations: headers only, and the remediation guidance is thinner than MDN's.
4. Qualys SSL Labs: the TLS deep dive
The retired TLS Observatory has an obvious replacement: the SSL Labs Server Test has been the reference TLS analyzer for years. It grades protocol support, cipher suites, key exchange, certificate chain correctness and known vulnerabilities, and it is free.
Best for: TLS and certificate configuration in depth.
Limitations: TLS only, and a full scan can take a few minutes per host. Our guide to earning an A+ TLS rating pairs well with it.
5. Internet.nl: the standards compliance angle
Internet.nl, run by the Dutch Internet Standards Platform, tests websites and mail domains against modern open standards: IPv6, DNSSEC, HTTPS and TLS settings, security headers, and on the email side SPF, DKIM, DMARC, STARTTLS and DANE, plus RPKI and security.txt. It produces a percentage score rather than a letter grade.
Best for: checking standards adoption across web and email in one pass.
Limitations: reports read more like a compliance checklist than a fix-it guide.
Also worth knowing: Hardenize, the configuration monitor created by SSL Labs author Ivan Ristić, was acquired and now lives inside Red Sift's commercial attack surface management product, so it is no longer the free quick-scan it once was. For the retired SSH Observatory, the open source ssh-audit project remains the practical community replacement.
Side-by-side comparison
| Tool | Focus | Grading | TLS analysis | Email auth | Dark web | Price |
|---|---|---|---|---|---|---|
| FortifyNet | Full external audit | A+ to F | Yes | Yes | Yes | Freemium |
| MDN HTTP Observatory | HTTP headers and policies | A+ to F | No | No | No | Free |
| securityheaders.com | HTTP headers | A+ to F | No | No | No | Free |
| Qualys SSL Labs | TLS and certificates | A+ to F | Yes | No | No | Free |
| Internet.nl | Open standards, web and email | Percentage | Yes | Yes | No | Free |
Counting six common audit areas (security headers, TLS, DNS, email authentication, dark web exposure, performance), coverage compares like this:
Number of the six audit areas each tool covers. The specialized tools go deeper within their single area; the chart shows breadth, not depth.
Rebuilding your old Observatory workflow
| If you used | For | Use this now |
|---|---|---|
| HTTP Observatory | Header grading and docs | MDN HTTP Observatory, or FortifyNet for headers plus everything else |
| TLS Observatory | Protocol and certificate analysis | Qualys SSL Labs or FortifyNet |
| Third-party tests tab | Aggregated multi-tool view | FortifyNet's single dashboard |
| SSH Observatory | SSH configuration | The open source ssh-audit tool |
Whichever combination you choose, header fundamentals still decide most of the grade. Our guides to HTTP security headers and HSTS cover the exact values scanners reward.
FAQ
Is Mozilla Observatory still available?
The HTTP scanning part lives on as the MDN HTTP Observatory and remains free. The original observatory.mozilla.org, including the TLS and SSH Observatories, was sunset in September 2024. Old scan history was preserved on MDN.
Does the MDN HTTP Observatory check TLS or certificates?
No. Mozilla's FAQ states the new tool focuses on HTTP data and that there are no plans to restore TLS or certificate analysis. Pair it with SSL Labs or a FortifyNet scan for that layer.
Is an A+ grade proof that a site is secure?
No. Mozilla itself is explicit on this point: header scanners test preventative configuration, not vulnerabilities such as outdated software, injectable forms or weak passwords. Treat an A+ as a strong baseline, not a certificate of security.
What is the best free Mozilla Observatory alternative?
For headers only, the MDN HTTP Observatory. For TLS, SSL Labs. If you want one scan that covers headers, TLS, DNS, email authentication and dark web exposure together, FortifyNet's free 60-second scan is the shortest path.
Check all six areas in one minute
The old Observatory taught the web that grades drive fixes. If you would rather not juggle three single-purpose scanners to rebuild it, run a free FortifyNet scan: headers, TLS, DNS, email authentication, dark web exposure and performance in about 60 seconds, no signup required.
Originally published at fortifynet.com/blog/mozilla-observatory-alternative. I'm the founder of FortifyNet, a website security scanner; this article comes from our blog, so factor in that founder bias when you read any tool recommendations here.
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