01 / Choose PreFlight when
Release proof is the job.
Teams that want header findings connected to the rest of a launch and production workflow.
Independent decision brief / no affiliate links
PreFlight versus MDN HTTP Observatory
MDN HTTP Observatory evaluates HTTP headers and related security configurations, returns a grade, and links to implementation guidance. PreFlight includes header analysis but adds exposed-secret discovery, routes, providers, journeys, payments, deploy policy, monitoring, and evidence over time.
Research date2026-08-05PricingVerify liveMethodPublic product evidence
02 / Choose MDN HTTP Observatory when
MDN HTTP Observatory owns the brief.
Developers who want a free, focused, transparent check of modern HTTP security-header configuration.
Capability matrix
Compare the work, not the logo wall.
Decision lensPreFlightMDN HTTP ObservatoryWhat should decide it
Scope
Public launch surface, connected systems, journeys, revenue, deploys, and monitoring.
HTTP headers and key HTTP security configurations.
Observatory is intentionally narrower.
Scoring
Prioritized evidence and release impact across multiple systems.
Documented grade and score derived from specific header tests and modifiers.
Use the grade as a hardening signal, not a security guarantee.
Guidance
Finding-specific fix context, verification, owners, and reruns.
Links each issue to MDN practical implementation guidance.
Both explain remediation; PreFlight keeps it in a release record.
Secrets and code
Reads public bundles, source maps, rendered HTML, and reachable files for exposure signals.
Does not claim to test exposed application secrets or code vulnerabilities.
Use a wider scanner for those risks.
Private application logic
Connected checks and browser journeys can test configured behavior.
Not in scope; MDN notes many security considerations are not tested.
Neither a header grade nor an outside-in audit replaces deep authenticated testing.
History and operations
Project history, release gates, incidents, reports, and recovery evidence.
Public domain scan history and API results.
PreFlight is built for internal ownership across releases.
The verdict. No fake winner.
Run Observatory even if you use PreFlight: it is focused, public, and clear about its limits. Choose PreFlight for the surrounding operational loop and SaaS-specific paths. An A+ Observatory grade does not mean the application is secure, and MDN explicitly says so.
Source ledger
Claims you can inspect yourself.
MDN HTTP Observatory
Inspect source Header-focused assessment and actionable security-configuration feedback.
Observatory FAQ
Inspect source Explicit limits of an A+ grade, API scope, public scan history, and HTTP focus.
Tests and scoring
Inspect source Documented tests, score modifiers, and grade methodology.
PreFlight feature inventory
Inspect source Public audit, Journey Canary, deploy gates, revenue verification, monitoring, evidence, and connected-provider capabilities.