WWW-Authenticate Inspect

Break down WWW-Authenticate schemes and parameters in your browser to identify missing auth requirements in 401 responses. Your input stays on your device.

Status

Runs in your browser. No input is sent to a server. Use this as a first-pass diagnostic step.

How to use

Paste WWW-Authenticate or Response Headers and click “Parse”. It summarizes schemes and parameters.

Notes (this tool)

  • Accepts WWW-Authenticate: header lines (multi-line paste is OK).
  • If multiple challenges are present, they are listed by scheme.

About this page

What does this tool do?

Split WWW-Authenticate to list schemes (Basic/Bearer/Digest, etc.) and parameters (realm/error, etc.).

Useful for diagnosing 401 errors and confirming auth requirements (realm/charset/errors).

Basics (401 and WWW-Authenticate)

  • 401 responses typically include WWW-Authenticate.
  • WWW-Authenticate tells the client how to authenticate.
  • Multiple schemes can be offered at once.

Input examples

  • WWW-Authenticate: Basic realm="admin", charset="UTF-8"
  • WWW-Authenticate: Bearer realm="api", error="invalid_token"
  • Paste full Response Headers

Common auth schemes

  • Basic: ID/password (Base64). Use over HTTPS.
  • Bearer: access tokens (e.g., JWT)
  • Digest: challenge-response (legacy)
  • Negotiate/NTLM: integrated auth (often internal environments)

Parameters (quick)

  • realm: authentication scope
  • charset: encoding for Basic (e.g., UTF-8)
  • error / error_description: details for Bearer errors

Common pitfalls

  • 401 without WWW-Authenticate
  • Using Basic without HTTPS
  • Missing Bearer error details in error_description
  • Client only tries one scheme when multiple are offered

Debugging workflow (recommended)

  • Extract WWW-Authenticate via Response Headers Parser
  • Summarize schemes/params with this tool
  • For Bearer, inspect with JWT Decoder / JWT Verifier
  • HTTP Status Inspect
  • Response Headers Parser
  • Request Headers Parser
  • JWT Decoder
  • JWT Verifier

What this tool does

  • Parse WWW-Authenticate schemes/params
  • List multiple challenges
  • Highlight common pitfalls

Operational notes

  • Result output alone is not enough for trust decisions. Always validate signatures and issuer.
  • Clock skew and environment differences affect reproducibility, so record test time and settings.

Referenced specs

  • RFC 9110 (HTTP Semantics)
  • RFC 7617 (Basic)
  • RFC 6750 (Bearer Token)
  • MDN: WWW-Authenticate

FAQ

Is a 401 without WWW-Authenticate wrong?

Many clients rely on WWW-Authenticate. Without it, auth flow is unclear and user-unfriendly.

Are Bearer error fields required?

Not required, but highly useful for troubleshooting.

What if multiple schemes are present?

Client behavior varies; check the order and what the client supports.

References

  1. RFC 9110
  2. RFC 7617
  3. RFC 6750
  4. MDN: WWW-Authenticate
  5. MDN: HTTP authentication

Page-specific case studies

Use this page to parse 401 challenge details and verify what the server is requesting from clients.

  • Check whether realm values match API boundaries.
  • Verify consistency of error and error_description fields.
  • Confirm scope hints reflect real authorization requirements.

Page-specific implementation checklist

  • Define challenge format for 401 responses in your spec.
  • Provide localized error details outside challenge headers.
  • Provide representative challenge examples for client implementers.
  • Add monitoring for malformed challenge values.

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

  1. JWT 401/403 Diagnostic Playbook — Separate 401 and 403 using Authorization, WWW-Authenticate, claims, and signature checks
  2. JWT Decoder vs Verifier: Difference & When to Use — When JWT is readable but returns 401/403, decide quickly whether to inspect decode results or signature verification.
  3. Authorization Inspect — Parse Authorization header formats
  4. JWT Verifier — Verify JWT signatures (HS/RS/ES)
  5. JWT Clock Skew Check — Detect timestamp skew across iat/nbf/exp
  6. JWT TTL Check — Calculate validity window and remaining TTL from exp/iat/nbf
  7. OAuth Bearer Diagnostic — Diagnose consistency between Bearer and WWW-Authenticate
  8. JWT 401/403 Troubleshooting — Troubleshoot 401/403 auth failures from headers and JWT claims

Auth

Trace auth failures across Bearer, WWW-Authenticate, and JWT