X-Content-Type-Options Inspect

What does this tool do?

Parse X-Content-Type-Options and check whether `nosniff` is correctly set.

Detect invalid or multiple values to verify MIME sniffing protection is configured as intended.

Typical use cases

• Checking for missing `nosniff` during security-header audits
• Troubleshooting inconsistent behavior around incorrect Content-Type settings
• Verifying header transformations through CDN or reverse proxies

Core idea

• `X-Content-Type-Options: nosniff` prevents browser MIME guessing.
• It enforces stricter handling of server-declared Content-Type, reducing risk from mis-served resources.

Recommended workflow

• Paste response headers and check for `nosniff`
• If invalid/multiple values appear, inspect delivery layers (app/CDN)
• Use with Content-Type Inspect to validate MIME declarations as well

Common pitfalls

• Serving non-standard values while expecting nosniff protection
• Duplicate headers making effective value unclear
• Trying to rely on nosniff without fixing wrong Content-Type declarations

What this tool does

• Determine whether nosniff is effectively present
• Detect unknown/invalid tokens
• Provide audit-friendly summary output

Operational notes

• nosniff is not sufficient alone; combine with CSP and proper MIME delivery.
• For static assets, correct extension-to-MIME mapping remains essential.

Referenced specs

• MDN: X-Content-Type-Options
• MIME Sniffing Standard

FAQ

References

1. MDN: X-Content-Type-Options
2. MIME Sniffing Standard

Next to view (diagnostic order)

These links are generated from site_map rules in recommended diagnostic order.

1. Content-Type Inspect — Parse Content-Type and inspect MIME/charset
2. Security Headers Audit — Audit presence of major security headers
3. Security Headers Fix Plan — Create a prioritized header-fix plan
4. CSP Inspect — Parse and evaluate CSP directives
5. Response Headers Parser — Parse response headers into structured data
6. How to Diagnose JS/CSS Blocks from nosniff Mismatch — Trace Content-Type vs nosniff mismatches, fallback responses, and delivery-layer rewrites
7. How to choose response header tools — Map Retry-After, Server-Timing, Link, Content-Type, and nosniff checks by symptom
8. X-Frame-Options Inspect — Parse X-Frame-Options to validate clickjacking protection

Same-theme links

Security Headers

Go from missing-header detection to concrete fix planning

• Security Headers Audit — Audit presence of major security headers
• Security Headers Recommendation — Suggest recommended values for missing headers
• Security Headers Fix Plan — Create a prioritized header-fix plan
• CSP Nonce/Hash Helper — Generate and verify CSP nonce/hash values
• CSP Builder — Build CSP policies from templates
• CSP Report Analyzer — Analyze CSP report JSON and summarize violation patterns
• CSP Inspect — Parse and evaluate CSP directives
• HSTS Inspect — Parse HSTS to verify HTTPS enforcement
• Permissions-Policy Inspect — Parse Permissions-Policy and review feature restrictions
• Referrer-Policy Inspect — Parse Referrer-Policy and check referrer exposure
• X-Frame-Options Inspect — Parse X-Frame-Options to validate clickjacking protection

Response Header Diagnostics

Step through raw headers to inspect Retry-After, Server-Timing, Link, and Content-Type

• HTTP Header Parser — Parse raw headers into structured lists
• Response Headers Parser — Parse response headers into structured data
• Set-Cookie Inspect — Parse Set-Cookie attributes and review delivery policy
• Cookie Domain/Path Matcher — Evaluate cookie send conditions by Domain/Path/Secure
• SameSite Cookie Simulator — Simulate cookie send behavior from SameSite and request context
• Set-Cookie Conflict Checker — Detect same-name cookie conflicts and overwrite risks
• Cookie Size Checker — Estimate Cookie header size and check limit risks
• Retry-After Inspect — Parse Retry-After and inspect retry wait behavior
• Server-Timing Inspect — Parse Server-Timing and inspect latency metrics
• Link Header Inspect — Parse Link headers and inspect rel/as/type
• Content-Type Inspect — Parse Content-Type and inspect MIME/charset
• HTTP Status Inspect — Analyze HTTP status codes and suggest handling direction

Example

X-Content-Type-Options: nosniff