Request/Response Diff

Parse and diagnose HTTP headers and routing signals in your browser. No input is sent to a server. Use it for first-pass observation-gap troubleshooting.

Status

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

How to use

Paste headers or summarized bodies to compare and click Diff. Use differences to isolate missing settings or env gaps.

Notes (this tool)

  • Some order-only differences are semantically irrelevant. Check whether each diff is meaningful.
  • Exclude noisy headers (e.g., Date) before diffing to speed up root-cause identification.

About this page

What does this tool do?

Compares headers in request and response and organizes additions, missing fields, and value changes.

Recommendations (practical)

  • Paste request then response separated by a blank line
  • If differences are large, check Vary/CORS/Cache-Control

Debugging workflow (recommended)

  • Start by finding unintended changes in the diff list
  • Then classify whether the issue is Cache/CORS/Auth related
  • Finalize root cause with dedicated inspect tools
  • Request Headers Parser
  • Response Headers Parser

What this tool does

  • List additions/removals/changes

Notes

  • Comparison is header-string based and does not evaluate app authorization logic or body content.
  • Multi-line or repeated headers are affected by input ordering; normalize logs before pasting.

Referenced specs

  • RFC 9110 (HTTP Field Name / Field Value)
  • RFC 9110 (Vary / Content Negotiation)

FAQ

Are headers counted as diff when only order changes?

Yes. Header ordering is part of the comparison. If you want to ignore order-only changes, normalize inputs before diffing.

Why does behavior change even when header diff is small?

Cache layers, auth logic, or response body changes can still alter behavior. Use header diff as the first diagnostic step.

References

  1. RFC 9110
  2. RFC 9111

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

  1. Request Headers Parser — Parse request headers into structured data
  2. Cookie Inspect — Parse Set-Cookie attributes and spot misconfigurations
  3. Set-Cookie Builder — Build Set-Cookie headers with attributes
  4. Set-Cookie Conflict Checker — Detect same-name cookie conflicts and overwrite risks