SimplyScan vs Mozilla Observatory | HTTP Checks and Site Health

Quick answer: MDN HTTP Observatory evaluates supported HTTP security configuration. SimplyScan checks supported public findings across eight site-health dimensions, including security, speed, SEO, and AI visibility. Compare their documented tests, investigate individual findings, and review application logic and data access separately.

By Paula C · Kraftwire Software

MDN HTTP Observatory evaluates supported HTTP security configuration and reports a grade with test results. A high grade does not establish that a site is secure; review application logic and data access separately.

A Content-Security-Policy result describes part of browser security configuration. Assess deployed secret exposure and database access separately; a header result does not establish the state of either.

Is Mozilla Observatory Still Good In 2026?

MDN HTTP Observatory tests supported headers, cookies, redirection, and Subresource Integrity. Its grade reflects its scoring rules; see the tests and scoring documentation.

Each scan reports observations from that scan. Observatory also provides a public v2 API that can be used in a scripted workflow; see its API documentation.

Why Look For A Mozilla Observatory Alternative?

Choose checks according to scope: HTTP configuration, secrets, data access, application logic, and performance require different evidence.

These live figures describe all scanned sites. They do not establish prevalence for an AI-built subgroup, compare development methods, or attribute findings to AI generation.

30% of the 119 live sites SimplyScan has scanned (36 sites) have at least one high or critical security issue.

A site can have standard headers and still be vulnerable to data leaks or broken authentication.

Review Database Access Separately

A Strict-Transport-Security header does not establish database permissions. Review RLS policies, table privileges, and bypass roles, then test allowed and denied operations.

Speed And Performance

Measure performance separately from security. A load-time measurement does not establish whether an application’s authorization or other defenses work.

79% of the 119 live sites SimplyScan has scanned (94 sites) have at least one medium-severity speed issue, such as render-blocking scripts or no route-based code splitting.

Use appropriate performance measurements for Largest Contentful Paint (LCP) and Cumulative Layout Shift (CLS). They are different observations from HTTP security-configuration tests.

How Does SimplyScan Compare To Mozilla Observatory?

SimplyScan accepts a deployed URL for supported site-health checks. See vibe-coding.

SimplyScan and Observatory have different test sets. Compare individual checks rather than assuming complete overlap.

SimplyScan grades 8 dimensions: security, speed, SEO, AI visibility (AEO), accessibility, GDPR signals, domain health, and email security.

Security Beyond Headers

SimplyScan checks recognizable secret patterns, supported anonymous backend responses, and environment-variable exposure. A URL scan does not inspect every Supabase policy or verify every XSS, CSRF, or authenticated authorization path.

AI Visibility (AEO)

SimplyScan includes AEO checks for supported crawler-access and structured-content signals. These do not measure actual answer-engine perception or guarantee indexing, ranking, or citation.

Which Additional Checks Should You Consider?

Choose tools for the evidence you need to collect.

SimplyScan

Supported public site-health observations from a deployed URL.

TLS Testing

Use a TLS assessment appropriate to the protocols, certificate chain, and configuration you need to inspect.

MDN HTTP Observatory

Supported HTTP configuration tests with documented scoring.

Performance Measurements

Measure field and laboratory performance as appropriate. SimplyScan includes field Core Web Vitals when CrUX data is available; it does not provide field metrics for every target.

Use platform-specific guidance alongside tests of the actual project. The Supabase checklist can organize review; completing it does not guarantee prevention of exposure.

Can I Automate My Security Scanning?

Observatory’s API can be called from a scripted workflow. Configure scheduling, result storage, and notifications separately where needed.

Choose scan triggers and alert handling for the changes you need to investigate; a scheduled scan is not an instantaneous deployment guarantee.

Pro Monitoring includes Pro scan credits for full reports. See pricing for the allowance associated with your chosen option.

SimplyScan offers Pro Monitoring with scheduled rescans, uptime monitoring, and supported Slack, GitHub, and Linear integrations. Investigate changed headers or detectable .env exposure after relevant changes; scans do not guarantee discovery before misuse.

Is My AI-Built App Actually Secure?

Review an AI-built app’s actual code and configuration against its security requirements. See vibe-coding safety.

11% of the 119 live sites SimplyScan has scanned (13 sites) have at least one medium-severity architecture issue, such as a library with a known vulnerability or no rate limiting.

Inspect individual architecture findings and their evidence; an aggregate rate does not identify a specific flaw in your app.

Review the application’s controls:

• Inspect client artifacts for secret exposure.
• Test database permissions and applicable Firebase rules or Supabase RLS policies.
• Review server-side trust boundaries and architecture risks.
• Publish a suitable vulnerability-reporting contact using security.txt guidance.

Conclusion: Which Tool Should You Use?

Use Observatory for its documented HTTP tests and evaluate other checks for the application’s remaining requirements.

SimplyScan provides supported findings for public secret patterns, anonymous backend exposure, and other site-health signals. Its Pro report adds supported report detail; it is not a professional manual audit.

Whether you are checking is bolt safe or auditing a custom Next.js build, start with a free scan at SimplyScan.

Inspect the report’s findings and limitations alongside code review and application-specific tests.

Frequently Asked Questions

What does Mozilla Observatory check exactly?

MDN HTTP Observatory evaluates supported HTTP configuration, including headers, cookies, redirection, and Subresource Integrity. Its documented grade is not proof that the application is secure.

Is SimplyScan a good alternative to Mozilla Observatory?

Compare the individual test sets. SimplyScan reports supported public findings across eight site-health dimensions, but it does not include every Observatory check or inspect every backend policy. Neither report establishes complete application security.

Does Mozilla Observatory offer API access?

Yes. MDN HTTP Observatory provides a public v2 API for scan requests and results. It can be used in scripted workflows; consult the current API documentation for integration details.

Why is my security score different between scanners?

Scanners use different tests and weights, so their grades are not directly interchangeable. SimplyScan combines severity-based deductions and score caps. Its score does not establish exploitability or the absence of vulnerabilities; inspect individual findings and coverage.

Can these tools find vulnerabilities in my source code?

Observatory examines supported HTTP responses. SimplyScan’s URL scan inspects supported public content and fetched assets; separate GitHub repository and MCP selected-file workflows provide other inputs. Review the scope of each and use application-specific tests for additional behavior.

Is there a free version of SimplyScan?

Yes. SimplyScan’s free URL scan reports supported observations across eight dimensions without signup and includes two rescans. Use them to check changes; a clean result does not prove every issue is resolved.

Pro Monitoring costs $24/month.

Pro report costs $14.99 one-time.