7 Best Free Website Security Scanners: Tested and Ranked for 2026

Coverage

A good scanner should check at least these categories:

• SSL/TLS configuration — certificate validity, protocol versions, cipher suites
• HTTP security headers — HSTS, CSP, X-Content-Type-Options, X-Frame-Options, Referrer-Policy, Permissions-Policy
• Cookie security — Secure, HttpOnly, SameSite flags
• Information disclosure — server version leaks, debug endpoints, directory listing
• DNS/Email security — SPF, DKIM, DMARC records
• Content security — mixed content, inline scripts

Actionability

A scanner that tells you "security headers are missing" is useless if it does not tell you which headers and how to add them. Look for:

• Specific findings, not just pass/fail
• Remediation guidance for each issue
• Priority levels (critical vs. informational)
• Platform-specific fix instructions (Nginx, Apache, Cloudflare, etc.)

Speed and ease of use

If a scan takes 30 minutes and requires installing software, you will not run it regularly. The best scanners work in your browser and deliver results in under 2 minutes.

Accuracy

False positives waste your time. False negatives give you false confidence. The best scanners minimize both through well-maintained check logic and regular updates.

1. ZeriFlow (Best Overall)

Website: zeriflow.com

ZeriFlow is a web security scanner designed specifically for small and medium businesses. It provides a security score out of 100 with detailed, actionable recommendations across 12+ categories.

What it checks

• SSL/TLS configuration (certificate, protocols, cipher suites, HSTS)
• All 6 critical HTTP security headers plus additional headers
• Cookie security (Secure, HttpOnly, SameSite flags)
• Content security (mixed content, CSP validation)
• DNS and email security (SPF, DKIM, DMARC)
• Information disclosure (server headers, debug pages, directory listing)
• Privacy and best practices (security.txt, robots.txt)

Strengths

• 60-second scans — results are almost instant
• Score out of 100 — easy to understand and track over time
• Specific remediation — tells you exactly what to fix and how
• Platform-specific guides — fix instructions for Nginx, Apache, Cloudflare, Vercel, and Next.js
• Clean interface — no clutter, no overwhelming technical jargon
• Free tier available — 3 scans per day at no cost

Limitations

• Focused on external scanning (does not analyze source code on the free tier)
• Pro plan required for advanced scans and domain monitoring

Verdict

The best balance of coverage, speed, and actionability for SMBs. Particularly strong on security headers and SSL configuration — the areas where most small businesses have gaps.

2. SecurityHeaders.com

Website: securityheaders.com

SecurityHeaders.com by Scott Helme is a focused tool that grades your HTTP security headers on a scale from A+ to F.

What it checks

• Strict-Transport-Security
• Content-Security-Policy
• X-Content-Type-Options
• X-Frame-Options
• Referrer-Policy
• Permissions-Policy
• Additional headers (Cross-Origin policies, etc.)

Strengths

• Dead simple — enter URL, get grade
• Clear letter-grade system
• Links to documentation for each header
• Good for quick header-specific checks

Limitations

• Headers only — does not check SSL, cookies, DNS, or anything else
• No remediation guidance beyond "add this header"
• No scoring across categories
• No historical tracking

Verdict

Excellent as a quick header check, but too narrow for a complete security assessment. Use it alongside a comprehensive scanner.

3. SSL Labs

Website: ssllabs.com/ssltest

Qualys SSL Labs is the gold standard for SSL/TLS testing. It performs an exhaustive analysis of your HTTPS configuration.

What it checks

• Certificate chain and trust
• Protocol support (TLS 1.0, 1.1, 1.2, 1.3)
• Cipher suite support and ordering
• Key exchange parameters
• Known vulnerabilities (BEAST, POODLE, Heartbleed, etc.)
• HSTS and HPKP
• OCSP stapling
• Certificate Transparency

Strengths

• The deepest SSL analysis available — nothing else comes close
• Industry-standard letter grades (A+ to F)
• Detailed technical breakdown
• Well-maintained and regularly updated

Limitations

• SSL/TLS only — does not check headers, cookies, DNS, or anything else
• Slow — scans take 60-90 seconds
• Technical output that can overwhelm non-experts
• No actionable remediation for most issues

Verdict

Essential for SSL configuration but too specialized for a complete picture. Run it once to nail your SSL config, then use a broader scanner for ongoing monitoring.

4. Observatory by Mozilla

Website: observatory.mozilla.org

Mozilla Observatory checks your website against Mozilla's web security guidelines. It covers headers, TLS, and some additional best practices.

What it checks

• HTTP security headers (all major ones)
• Content Security Policy analysis
• Cookie security
• CORS configuration
• Subresource integrity
• Referrer policy
• Redirection patterns

Strengths

• Built by Mozilla — credible and well-maintained
• Good CSP analysis
• Tests for modern best practices
• Links third-party tools (SSL Labs, etc.)

Limitations

• Results can be confusing for non-technical users
• Limited remediation guidance
• No DNS or email security checks
• Interface has not been updated in a while

Verdict

A solid, trustworthy option with good header and CSP analysis. Best suited for developers who understand the technical output.

5. ImmuniWeb

Website: immuniweb.com/websec

ImmuniWeb offers a free website security test that combines multiple checks into a single scan.

What it checks

• HTTP security headers
• SSL/TLS configuration
• GDPR and PCI DSS compliance indicators
• Privacy and cookie compliance
• Content security

Strengths

• Combines headers + SSL in one scan
• Compliance-oriented (mentions GDPR, PCI DSS)
• Letter grades for different categories

Limitations

• Free scan is limited in depth
• Results push heavily toward paid services
• Slower than most competitors
• Some checks feel surface-level

Verdict

Good for a compliance-oriented overview, but the free tier feels like a funnel to paid services. The actual findings are less detailed than dedicated tools.

6. Sucuri SiteCheck

Website: sitecheck.sucuri.net

Sucuri SiteCheck is a malware and blacklist scanner. It checks whether your site has been compromised, not whether it is vulnerable.

What it checks

• Known malware detection
• Blacklist status (Google, Norton, McAfee, etc.)
• Spam injection
• Defacement
• SEO spam
• Basic server-side security checks

Strengths

• Good for checking if you are already compromised
• Checks against multiple blacklists simultaneously
• Quick results
• Well-known and trusted brand

Limitations

• Reactive, not preventive — finds existing compromises, not vulnerabilities
• Minimal security header or SSL checking
• Limited free functionality
• Heavy upsell to Sucuri WAF service

Verdict

Valuable for checking if your site has been hacked, but does not help you prevent attacks. Use it as a complement to a preventive scanner, not a replacement.

7. OWASP ZAP

Website: zaproxy.org

OWASP ZAP (Zed Attack Proxy) is an open-source security testing tool maintained by the OWASP Foundation. It is the most comprehensive free option — but also the most complex.

What it checks

• Active vulnerability scanning (XSS, SQL injection, etc.)
• Passive analysis (headers, cookies, information disclosure)
• Spider/crawler for discovering pages
• API scanning
• Authentication testing
• Custom scan policies

Strengths

• The most comprehensive free scanner — period
• Active scanning finds vulnerabilities others cannot
• Highly configurable
• CI/CD integration available
• Large community and regular updates

Limitations

• Requires installation — it is a desktop application (or Docker container)
• Complex — designed for security professionals
• Slow — full scans can take hours
• Can break things — active scanning sends attack payloads to your site
• Not suitable for production environments without careful configuration

Verdict

The most powerful option by far, but not suitable for non-technical users. If you have a developer or security person on your team, ZAP is invaluable. For business owners, start with a simpler scanner.

How They Compare

Coverage score (categories checked)

Our Recommendation

For most small businesses: Start with ZeriFlow. It offers the broadest coverage in the fastest time with the most actionable results. Run a free scan to get your baseline score, fix the critical issues, and re-scan weekly.

For SSL-specific issues: Complement with SSL Labs for the deepest TLS analysis available.

For header details: SecurityHeaders.com is a great quick-check tool to verify header changes after deployment.

For developers and technical teams: Add OWASP ZAP to your toolkit for active vulnerability scanning in development and staging environments.

For checking if you have been compromised: Run Sucuri SiteCheck to verify you are not on any blacklists and do not have known malware.

The most effective approach is to use ZeriFlow as your primary scanner for continuous monitoring, and supplement with specialized tools when you need deeper analysis in a specific area.

Get your free security score now at zeriflow.com.

Further Reading

• Mozilla SSL Configuration Generator
• RFC 8996 — Deprecating TLS 1.0 and TLS 1.1

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