Set-Cookie Conflict Checker

What does this tool do?

Parses multiple Set-Cookie lines and detects conflicts where same-name cookies differ by Domain or Path.

With a request URL, it estimates which cookies are sent and highlights likely collision cases.

Typical use cases

• Login state changes across URL paths or subdomains
• Multiple services reuse the same cookie name
• Legacy Path or Domain cookies remain after migration

Detected conflict patterns

• Overwrites caused by duplicate keys (name+domain+path)
• Path variants of same name causing send-order dependency
• Mixed Secure and non-Secure variants causing environment drift
• Mixed host-only and Domain cookies increasing match complexity

What this tool does

• Parse Set-Cookie syntax and list attributes
• Warn about same-name conflicts and duplicate keys
• Simulate send candidates for a specified request URL

Debugging workflow (recommended)

• Paste all Set-Cookie lines from problematic responses
• Set source URL and request URL, then run Analyze
• Use conflict warnings to clean up Path/Domain strategy
• Validate SameSite and security attributes with related tools

Operational notes

• Default Path inference depends on source URL. When omitted, this tool assumes /.
• Cookie send ordering can vary by browser implementation and is not guaranteed identical.

Referenced specs

• RFC 6265 (HTTP Cookies)
• MDN: Set-Cookie

FAQ

References

1. RFC 6265 (HTTP Cookies)
2. MDN: Set-Cookie

Next to view (diagnostic order)

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

1. Set-Cookie Inspect — Parse Set-Cookie attributes and review delivery policy
2. Cookie Domain/Path Matcher — Evaluate cookie send conditions by Domain/Path/Secure
3. SameSite Cookie Simulator — Simulate cookie send behavior from SameSite and request context
4. Cookie Security Audit — Audit Secure/HttpOnly/SameSite settings
5. Cookie Size Checker — Estimate Cookie header size and check limit risks
6. How to Diagnose Same-Name Cookie Collisions — Resolve unstable behavior by tracing same-name cookie path/domain variants, overwrite order, and send collisions
7. How to Diagnose Set-Cookie Not Persisting — Isolate cookie persistence failures by checking Domain/Path/Secure/SameSite in order
8. Cookie Incident Operational Checklist — Standardize response from triage to permanent fixes across storage failures, OAuth return issues, and same-name collisions

Same-theme links

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
• 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
• X-Content-Type-Options Inspect — Parse X-Content-Type-Options and validate nosniff
• HTTP Status Inspect — Analyze HTTP status codes and suggest handling direction

Example

Set-Cookie: sid=app; Path=/; Secure
Set-Cookie: sid=admin; Path=/admin; Secure