How to Diagnose Set-Cookie Not Persisting

When Set-Cookie exists in response but login does not persist, the root cause is often a combination of attribute mismatch and browser restrictions.

Symptom definition

Diagnostic steps

  1. 1) Use Set-Cookie Inspect to validate Domain/Path/Secure/SameSite attributes
  2. 2) Use Cookie Domain/Path Matcher to test whether target URL should receive the cookie
  3. 3) Use Cookie Security Audit to verify policy requirements such as SameSite=None + Secure
  4. 4) Use Host/Authority/Origin Inspect to check origin mismatches
  5. 5) Use Cookie Size Checker to detect drop risks from oversized cookie headers

Common causes

Fix checklist

Tools to use

FAQ

Why is Set-Cookie visible but not persisted?
Typical causes are Domain/Path mismatch, Secure constraints, SameSite policy, and browser third-party restrictions. Validate them in order.
Why does it work locally but fail in production?
Production differs in subdomains, HTTPS, and CDN layers, which often exposes cookie-attribute mismatches not seen locally.

Referenced specs

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. Set-Cookie Conflict Checker — Detect same-name cookie conflicts and overwrite risks
  5. Cookie Security Audit — Audit Secure/HttpOnly/SameSite settings
  6. Cookie Size Checker — Estimate Cookie header size and check limit risks
  7. Host/Authority/Origin Inspect — Cross-check Host/:authority/Origin/Referer for mismatches
  8. Cookie Parser — Split Cookie headers into key=value pairs

Scenario Clusters

Operational incident scenarios that route you into the shortest diagnostic path