Mozilla Observatory Alternative: 7 Scanners Tested (2026)
Looking for a Mozilla Observatory alternative? We tested 7 free website security scanners — SecScanner, SSL Labs, ImmuniWeb, Sucuri — to find what matters.
You've decided to audit your website's security — great. Now you need to pick a scanner. The problem: there are dozens of tools, each with a different focus, different depth, and wildly different pricing. This article compares the most widely used website security scanners in 2026 side-by-side so you can make an informed decision.
Updated May 2026: What Changed
We expanded this comparison to now cover 7 tools: adding UpGuard and Pentest-Tools alongside SecScanner, SSL Labs, Mozilla Observatory, ImmuniWeb, and Sucuri. We updated the feature matrix to reflect SecScanner's current check count (62 checks, 24 free) and added detailed reviews for each new tool. The verdict hasn't changed — the right tool still depends on whether you need a quick passive audit, a security risk rating, deep TLS grading, or active exploit simulation.
Quick Comparison: Feature Matrix
Scroll horizontally to see all 7 tools.
| Feature | SecScanner | SSL Labs | Mozilla Observatory | ImmuniWeb | Sucuri | UpGuard | Pentest-Tools |
|---|---|---|---|---|---|---|---|
| TLS / HTTPS checks | ✅ 9 checks (free) | ✅ Deep TLS analysis | ⚠️ Basic HTTPS check | ✅ Yes | ⚠️ Basic | ⚠️ Basic | ✅ Good |
| HTTP Security Headers | ✅ 23 checks (free+paid) | ❌ Not covered | ✅ Primary focus | ✅ Yes | ❌ Not covered | ⚠️ Basic | ✅ Yes |
| CORS & Cross-Origin policies | ✅ 11 checks (paid) | ❌ Not covered | ⚠️ CORS origin only | ⚠️ Partial | ❌ Not covered | ❌ Not covered | ⚠️ Partial |
| Content analysis (JS libs, secrets) | ✅ 21 checks (paid) | ❌ Not covered | ❌ Not covered | ✅ Yes | ✅ Malware detection | ✅ Attack surface | ✅ Active scanning |
| DNS & Email security | ✅ 9 checks (paid) | ❌ Not covered | ❌ Not covered | ⚠️ Limited | ❌ Not covered | ⚠️ Limited | ⚠️ Limited |
| Cookie security | ✅ Yes | ❌ No | ✅ Yes | ✅ Yes | ❌ No | ❌ No | ✅ Yes |
| Dark web monitoring | ❌ No | ❌ No | ❌ No | ✅ Paid | ❌ No | ✅ Paid | ❌ No |
| Active / intrusive scanning | ❌ Passive only | ❌ Passive only | ❌ Passive only | ⚠️ Limited | ✅ WAF + cleanup | ❌ Passive only | ✅ Full pentest |
| Total checks (free) | 24 | ~20 TLS-only | ~11 | ~10 (community) | ❌ Paid only | ~20 (risk rating) | ⚠️ Trial only |
| Total checks (paid) | 62 | ~20 TLS-only | ~11 | Varies by plan | Continuous monitoring | Varies by plan | 20+ scan types |
| No signup required | ✅ Yes | ✅ Yes | ✅ Yes | ✅ Community tier | ❌ Account required | ❌ Account required | ❌ Account required |
| Compliance mapping | ✅ SOC 2, PCI DSS, ISO 27001 | ❌ No | ❌ No | ✅ GDPR, PCI DSS | ⚠️ Limited | ✅ Paid | ❌ No |
| Continuous monitoring | ✅ Paid | ❌ No | ❌ No | ✅ Paid | ✅ Core feature | ✅ Paid | ✅ Paid |
| Scan speed | ~30–60 seconds | ~60–120 seconds | ~10–20 seconds | ~1–5 minutes | Ongoing (WAF) | ~2–5 minutes | ~5–15 minutes |
| Free tier available | ✅ 24 checks | ✅ Full tool | ✅ Full tool | ✅ Community edition | ❌ Paid only | ✅ Limited | ⚠️ Free trial |
Tool Reviews
SecScanner — Best All-in-One Free Scanner
SecScanner runs 62 automated, non-intrusive checks across five categories: TLS/HTTPS, HTTP security headers, CORS and cross-origin policies, content analysis, and DNS/email security. 24 of those checks are available completely free with no signup required.
What sets it apart: It's the only scanner in this comparison that covers all five categories in a single passive scan. One URL submission gives you TLS quality, header analysis, cookie security, vulnerable JS library detection, SPF/DKIM/DMARC configuration, and subdomain takeover risk — all in under 60 seconds. You can also check your SSL certificate directly.
The paid tier unlocks the remaining 38 checks, adds continuous monitoring with email alerts, and provides compliance reports mapped to SOC 2, PCI DSS, and ISO 27001. See pricing for details.
Best for: developers and security teams who want a comprehensive security baseline across all categories, or anyone doing compliance prep for SOC 2 / PCI DSS.
Limitations: Non-intrusive only — it won't perform exploit testing, SQL injection fuzzing, or authenticated app scanning. For penetration testing, you need a different category of tool.
SSL Labs (Qualys) — Best for Deep TLS Analysis
SSL Labs by Qualys is the industry benchmark for TLS/SSL testing. It grades your server's TLS configuration (A+ to F) based on protocol support, cipher suite ordering, certificate chain validity, HSTS, and a dozen other TLS-specific factors.
What sets it apart: Unmatched depth for TLS. If you need to know exactly why a server is getting a B instead of an A+, or whether specific cipher suites are supported, SSL Labs is the tool.
Best for: auditing TLS configuration specifically — certificate expiry, protocol deprecation (TLS 1.0/1.1), cipher suite hardening.
Limitations: TLS-only. It will not tell you anything about your HTTP headers, cookies, DNS configuration, or vulnerable JavaScript libraries.
Mozilla Observatory — Best Free Header Scanner
Mozilla Observatory scores HTTP security headers and a few TLS basics. It covers CSP, HSTS, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy, cookies, and CORS — about 11 checks total.
What sets it apart: A clean, opinionated scoring system that's easy to explain to stakeholders. The Mozilla Observatory score (0–100) is widely recognized and easy to reference in security reviews.
Best for: developers doing a quick header audit, or teams that want a single shareable score for header hygiene.
Limitations: No TLS depth, no content analysis, no DNS checks. Doesn't cover CORS fully, and the free tier has rate limits.
ImmuniWeb — Best for Enterprise Compliance + Dark Web
ImmuniWeb offers a free community edition that tests web application security and SSL, plus paid enterprise plans that add continuous monitoring, dark web surveillance, and compliance reporting for GDPR and PCI DSS. The platform uses machine learning to prioritize findings.
What sets it apart: The combination of passive security scanning with dark web monitoring in a single platform. If you need to know whether your organization's credentials have been leaked alongside your website security posture, ImmuniWeb covers both.
Best for: enterprises with compliance requirements (GDPR, PCI DSS) who need both surface-level security scanning and dark web credential monitoring.
Limitations: The community edition has limited check coverage. Full functionality requires a paid subscription. Slower than simpler passive scanners.
Sucuri — Best for Malware Detection and WAF
Sucuri is a website security platform, not a configuration scanner. Its primary products are a cloud-based WAF (web application firewall) and a malware scanning and cleanup service. Sucuri continuously monitors your site for malware, blacklisting, and defacement — and if your site is infected, it cleans it up.
What sets it apart: Post-infection cleanup and active protection. If your WordPress or CMS site has been hacked, Sucuri is one of the fastest ways to clean it up and prevent reinfection.
Best for: sites that have been hacked or are under active attack. Also good for CMS sites (WordPress, Joomla, Drupal) that need ongoing WAF protection.
Limitations: Sucuri is not a configuration auditor — it won't tell you about misconfigured security headers, missing DNSSEC, or weak cipher suites. No free tier. Paid subscription required.
UpGuard — Best for Security Risk Ratings and Vendor Risk
UpGuard is a cyber risk management platform that assigns an external security rating to any domain. Rather than running deep technical checks, it aggregates signals across exposed services, TLS basics, open ports, and known data breaches to produce a risk score (0–950). It also checks email security configuration (SPF, DKIM, DMARC) and certificate validity.
What sets it apart: Vendor risk management — UpGuard lets you monitor the security posture of third-party suppliers at scale. If your organization needs to track security ratings for dozens of vendors, UpGuard's dashboard is purpose-built for that.
Best for: enterprises assessing third-party and supply chain risk, security teams that need a risk score for external reporting, or organizations with compliance requirements around vendor due diligence.
Limitations: Not a deep configuration auditor. It won't give you specific findings on header values, CORS policy, cookie flags, or DNSSEC configuration — it tells you a domain's overall risk posture, not exactly what to fix. Requires account registration. Paid plans needed for full functionality.
Pentest-Tools — Best for Active Web Application Scanning
Pentest-Tools is an online penetration testing platform that combines passive and active scanners. Unlike every other tool in this comparison, it actively attempts to identify exploitable vulnerabilities — not just misconfigured settings. It includes a web vulnerability scanner, TLS/SSL scanner, network scanner, and host discovery tools.
What sets it apart: Active scanning capability in a SaaS platform without requiring a local Burp Suite or OWASP ZAP installation. Security engineers can run scans, schedule them, and manage findings from a browser-based interface with team collaboration features.
Best for: security engineers and pentesters who need a cloud-based active scanning platform, teams running regular application security assessments without managing local tooling, and organizations preparing for formal penetration tests.
Limitations: Active scanning requires explicit authorization — never scan a site you don't own or have permission to test. Scans take 5–15 minutes minimum. Requires a paid account (free trial available). Not suitable for passive monitoring in CI/CD workflows.
Qualys Web Application Scanner (WAS) — Best for Enterprise Pen Testing
Qualys WAS is an active (intrusive) web application scanner. Unlike the other tools in this comparison, it actually attempts to exploit vulnerabilities — SQL injection, XSS, authentication bypass, business logic flaws. This makes it significantly more powerful but also more complex and expensive.
Best for: large enterprises running formal penetration tests, PCI DSS QSA assessments, or teams with dedicated application security engineers.
Limitations: Requires an account and paid subscription, must be carefully authorized before use, scans can take hours, and results require security expertise to interpret. Not suitable for quick, frequent checks in a development workflow.
How to Choose the Right Scanner
The right tool depends on what you're trying to achieve:
- Quick security baseline (free) → SecScanner free tier (24 checks, no signup)
- TLS-only deep dive → SSL checker or SSL Labs
- HTTP header score for stakeholders → Mozilla Observatory
- Full security audit + compliance → SecScanner paid (62 checks + compliance mapping)
- Dark web monitoring + compliance → ImmuniWeb enterprise
- Malware cleanup / WAF protection → Sucuri
- Security risk rating / vendor risk management → UpGuard
- Active web application pentesting → Pentest-Tools or Qualys WAS
- Enterprise pen test / active exploit scanning → Qualys WAS, Burp Suite, or a dedicated DAST tool
For most development teams, the answer is to use two tools: SecScanner for continuous configuration monitoring (fast, non-intrusive, covers all passive checks), and SSL Labs for periodic deep TLS audits. Together they cover 95% of what you need without paying for enterprise tooling. See our full list of 62 security checks to understand exactly what SecScanner tests.
What Makes a Comprehensive Security Scanner?
Regardless of which tool you choose, look for these criteria:
1. Check Coverage Across Categories
A scanner that only checks TLS certificates is useful but limited. Comprehensive coverage means:
- TLS/HTTPS — Certificate validity, protocol versions, cipher suites, HSTS, mixed content
- Security Headers — CSP, X-Content-Type-Options, Referrer-Policy, Permissions-Policy
- Content Analysis — Vulnerable JavaScript libraries, exposed admin panels, sensitive file exposure
- DNS & Email Security — SPF, DKIM, DMARC, CAA records, subdomain takeover risks
- CORS & Cross-Origin Policies — Access-Control headers, COEP, COOP, CORP
2. Non-Intrusive vs. Intrusive
Non-intrusive (passive) scanners analyze publicly visible configuration — headers, TLS, DNS — without risk to production. Intrusive (active) scanners attempt exploits and require authorization. For daily monitoring, non-intrusive tools are ideal; for formal security assessments, you'll need intrusive tools too.
3. Speed
Results in 60 seconds or less enable CI/CD integration. Anything slower becomes a bottleneck.
4. Compliance Mapping
If you need to demonstrate compliance with SOC 2, ISO 27001, or PCI DSS, the scanner should map each finding directly to the relevant framework requirement — saving hours of manual correlation.
5. Actionable Remediation
A pass/fail list with no context doesn't help developers fix issues. Look for scanners that explain the risk and provide specific configuration examples.
The Bottom Line
For most web teams in 2026, SecScanner covers the most ground with the least friction — 24 checks free, 62 with a subscription, results in under a minute. SSL Labs remains the go-to for deep TLS analysis. Mozilla Observatory is a good secondary check for header scoring. ImmuniWeb suits enterprises that need dark web monitoring alongside security auditing. Sucuri is the right tool if your site is infected or needs an active WAF. UpGuard is best when you need to track the security posture of third-party vendors at scale. Pentest-Tools fills the gap when you need active exploitation testing in a SaaS platform. Qualys WAS is for teams doing formal enterprise pen tests.
Don't overthink it: run a free SecScanner scan now (no signup required), fix the findings, and set up monitoring so you catch regressions automatically. Or explore all 62 security checks to see exactly what gets tested — and why each one matters.
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