DNS_PROBE_FINISHED_NXDOMAIN Fix Checklist
How to diagnose NXDOMAIN errors by checking DNS records, nameserver delegation, resolver cache, and domain registration state.
DiagnoseGuides Hub
Short guides to help you interpret lookup results and resolve issues. Each guide follows the Problem → TOP 3 Causes → Tool Links → Resolution Checklist structure.
Most Common Issues
SPF Permerror: Too Many DNS Lookups
How to fix SPF permerror by reducing include chains, removing unnecessary mechanisms, and keeping total DNS lookups under 10.
DiagnoseRedirect Loop Diagnosis
A troubleshooting guide for ERR_TOO_MANY_REDIRECTS that helps isolate loop sources across origin servers, CDN rules, cookies, and HTTPS enforcement.
DiagnoseSSL Expiry Operations Checklist
An operations checklist for expiring or expired certificates, covering renewal automation, deployment verification, and HTTPS reachability checks.
DiagnoseRDAP vs WHOIS: Key Differences
A comparison guide covering the response model, operational advantages, and practical decision points for using RDAP instead of legacy WHOIS.
DiagnoseDNS/SSL/HTTP Comprehensive Diagnostic Checklist
An operations-focused guide for isolating domain outages by checking DNS, SSL, and HTTP in a fixed order and narrowing the failing layer quickly.
DiagnoseBrowse by Symptom
Domain does not resolve
Use DNS, propagation, and nameserver guides to separate record errors from cache delays.
Mail delivery or auth fails
Trace SPF, DMARC, blacklist, and DNS issues before changing mail infrastructure.
HTTPS or certificate warning
Check expiry, SAN mismatch, wildcard coverage, and certificate chain issues.
Redirect loop or access failure
Start with redirect behavior, response codes, and broad DNS/HTTP diagnosis guides.
Browse by Tool
Categories
IP / Network
Public IP changes, proxy/VPN, routing issues.
Domain / RDAP
Registration status flags, expiry/protection checks.
DNS Records
A/MX/SPF/DMARC troubleshooting.
SSL / HTTP
Expiry, chain issues, security headers, redirects.
Recently Updated
301 vs 302 Redirect Guide
When to use permanent vs temporary redirects, and how 301 and 302 differ for caching, routing, and SEO signals.
Diagnose403 Forbidden Checklist
How to diagnose 403 responses by reviewing origin permissions, WAF rules, CDN access controls, and routing behavior.
Diagnose404 Not Found Root Cause Guide
How to diagnose whether a 404 comes from missing deployment artifacts, broken rewrites, or the wrong final route.
Diagnose502 Bad Gateway Checklist
How to diagnose 502 responses by checking reverse proxy to upstream connectivity, service health, and target routing.
Diagnose503 Service Unavailable Checklist
How to diagnose 503 responses by separating maintenance mode, overload, rate limiting, and backend readiness issues.
DiagnoseCDN Cache vs DNS Propagation
How to tell whether delayed changes are caused by DNS propagation or cached CDN content, and what to check first.
DiagnoseDNS (13)
SSL (6)
HTTP (12)
IP / Network (2)
RDAP / WHOIS (2)
General (2)
How to Use Guides
1. Look Up
Look up IP, DNS, SSL, HTTP in Utilities.
2. Check Results
Review the status badge and checklist on the results page.
3. Apply Guide
Follow the resolution checklist in the related guide.
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