Gecko Advisor vs Mozilla Observatory
Observatory checks your headers. Gecko Advisor checks everything a visitor experiences.
Quick Comparison
| Feature | Gecko Advisor | Mozilla Observatory |
|---|---|---|
| Focus | Full privacy & security analysis | HTTP security headers only |
| Scope | Trackers, cookies, fingerprinting, headers, TLS | CSP, HSTS, X-Frame-Options, X-Content-Type-Options |
| Privacy scoring | 0-100 privacy score with grade | A+ to F header score |
| Tracker detection | Yes, with third-party identification | No |
| Cookie analysis | Yes, categorized by purpose | No |
| Fingerprinting | Yes, canvas/WebGL/audio | No |
| TLS grading | Yes, TLS version and cipher analysis | Partial (HSTS only) |
| Change tracking | Historical score changes, trend analysis | No history |
| API | REST API with per-domain data | Public API (limited) |
| Pricing | Free scanner, API from $49/mo | Completely free |
Where Mozilla Observatory Excels
Mozilla Observatory is a focused, free tool for evaluating HTTP security header configuration. Built by Mozilla's security team, it provides specific, actionable recommendations for hardening your website's header configuration.
- Free and open-source -- Completely free to use with no usage limits, backed by Mozilla's reputation and open-source development model
- Focused HTTP header analysis -- Deep evaluation of Content-Security-Policy, Strict-Transport-Security, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, and other security headers
- Actionable CSP recommendations -- Provides specific guidance on building and improving Content-Security-Policy headers, including inline script handling and nonce configuration
- Community trust -- Developed and maintained by Mozilla, with widespread adoption in the web security community and integration with other Mozilla security tools
- Third-party integration -- Aggregates results from additional scanners like SSL Labs, ImmuniWeb, and Security Headers into a single view
For developers focused on hardening their own website's security headers, Mozilla Observatory provides a best-in-class, focused analysis with clear remediation guidance.
Where Gecko Advisor Excels
Gecko Advisor evaluates the complete visitor experience, not just HTTP headers. It renders the page in a real browser, observes all network requests, and analyzes the full privacy and security posture of a domain.
- Comprehensive privacy analysis -- Evaluates trackers, cookies, fingerprinting, security headers, and TLS in a single scan rather than headers alone
- Third-party tracker ecosystem mapping -- Identifies every third-party request, classifies trackers by category (advertising, analytics, social), and cross-references against known tracking databases
- Cookie audit -- Full analysis of first-party and third-party cookies including purposes, lifetimes, and security attribute coverage (HttpOnly, Secure, SameSite)
- Fingerprinting detection -- Identifies canvas, WebGL, and audio fingerprinting techniques that operate independently of security headers and cookies
- Historical change tracking -- Monitors how a domain's privacy posture changes over time, with trend analysis and stability scoring for vendor due diligence
- Vendor risk context -- Built for assessing third-party vendor domains, not just your own site, with features designed for privacy teams and compliance workflows
- Deterministic scoring -- A transparent 0-100 privacy score with published methodology showing exactly how each finding contributes to the overall score
Use Both Together
Mozilla Observatory and Gecko Advisor are complementary tools that together provide a thorough security and privacy assessment.
For your own website
Run Mozilla Observatory first to get specific header hardening recommendations. Implement those recommendations, then run Gecko Advisor to assess the broader privacy posture -- including whether third-party scripts you load are undermining the security headers you just configured.
For vendor assessment
Use Gecko Advisor as your primary tool for vendor privacy assessment. Its comprehensive analysis covers everything Observatory checks (security headers) plus everything it does not (trackers, cookies, fingerprinting, TLS grading). Observatory can supplement with detailed CSP recommendations if you need to advise a vendor on specific header improvements.
For ongoing monitoring
Observatory provides a point-in-time header check with no history. Gecko Advisor tracks changes over time, showing whether a domain's privacy practices are improving, declining, or volatile. For ongoing vendor monitoring, Gecko Advisor's change detection and stability scoring provide the longitudinal view that Observatory lacks.
A Note on Scope
It is worth understanding what each tool's score actually measures. A website can receive an A+ from Mozilla Observatory (all security headers perfectly configured) while simultaneously receiving a low score from Gecko Advisor (loading dozens of trackers, setting persistent cookies, and deploying fingerprinting).
This is not a contradiction. Observatory measures whether the server sends the right HTTP headers. Gecko Advisor measures what happens in the visitor's browser. A site can have excellent header configuration while still loading third-party scripts that track visitors across the web.
Security headers are necessary but not sufficient for privacy. They protect against certain attack vectors (clickjacking, XSS, protocol downgrades) but do not prevent the site itself from loading advertising trackers, setting third-party cookies, or deploying fingerprinting techniques. A complete privacy assessment requires examining both.
Frequently Asked Questions
Is Gecko Advisor a Mozilla Observatory replacement?
For security header analysis specifically, both tools evaluate similar headers, but Observatory provides more granular CSP recommendations. For overall privacy and security assessment -- including trackers, cookies, fingerprinting, and TLS -- Gecko Advisor provides substantially broader coverage. Many teams use both: Observatory for header-specific hardening guidance, and Gecko Advisor for comprehensive privacy risk assessment.
Why would I pay for Gecko Advisor when Observatory is free?
Gecko Advisor's free scanner provides the same zero-cost entry point for individual scans. The paid API is for teams that need programmatic access to privacy data -- integrating vendor screening into procurement workflows, monitoring vendor domains at scale, or building privacy risk dashboards. Observatory does not offer this level of integration or data depth, and its scope is limited to HTTP headers.
Which is more accurate for security headers?
Both tools evaluate core security headers (CSP, HSTS, X-Frame-Options, X-Content-Type-Options, Referrer-Policy). Observatory provides more detailed CSP analysis and specific implementation recommendations. Gecko Advisor provides broader context by showing how security header configuration interacts with the site's overall privacy posture -- for example, whether a site has CSP configured but still loads trackers allowed by that policy.