Diagnostic and testing
- WebPageTest — Full page speed waterfall analysis from multiple global locations
- SSL Server Test (SSLLabs) — Comprehensive SSL/TLS configuration analysis
- Mail Tester — Email deliverability score and spam check
- MXToolBox — DNS lookups, blacklist checks, SPF/DKIM validators
- DMARC Analyzer — DMARC record checker and reporting
- WhatsMyDNS — Global DNS propagation checker
- Gift of Speed — Check if render-blocking resources are slowing your site
WordPress development and debugging
- WP-CLI Commands — Full command reference for WP-CLI
- Query Monitor — Debug plugin for WordPress: database queries, PHP errors, hooks, enqueued scripts
- Better Search Replace — Search and replace in the WordPress database (use with caution)
- WP-CLI — The command-line interface for WordPress
- Block Editor Handbook — Official WordPress Gutenberg/Block Editor documentation
Hosting and infrastructure
- EasyEngine Docs — nginx-based WordPress server management
- nginx documentation — Official nginx admin and config reference
- DigitalOcean Community Tutorials — Practical Linux, nginx, Docker tutorials
- Docker Compose documentation — Multi-container Docker setup
- PostgreSQL documentation — Database reference (if using PostgreSQL)
- MySQL 8.0 Reference Manual — Official MySQL docs
Security
- OWASP Top 10 — The most critical web application security risks
- OWASP Web Security Testing Guide — Comprehensive framework for testing web application security
- SSL Labs SSL and TLS Deployment Best Practices — Practical SSL hardening guide
- Certbot (EFF) — Get and auto-renew free Let's Encrypt certificates, with config instructions per server
- Have I Been Pwned — Check if your email or domain has been in a data breach
Performance and caching
- Lighthouse — Google's open-source performance auditing tool
- GTmetrix — Page speed testing with historical tracking
- HTTP/3 explained (Cloudflare Learning) — Why modern protocols matter for site speed
- RAIL Performance Model — User-centric performance measurement from Google
DNS and domains
- What is DNS? (Cloudflare Learning) — Clear explanation of how DNS works
- Let's Encrypt Documentation — Free SSL certificate documentation
- SPF record validator (MXToolBox) — Check your SPF configuration and DNS lookup count
- DKIM Core — DKIM record validator and key checker
Email deliverability
- Google Postmaster Tools — Gmail sender reputation data
- Microsoft SNDS — Outlook/Hotmail sender reputation portal
- Email on Acid — Email rendering and deliverability testing
- DMARC explained (Mailchimp) — Practical guide to email authentication and DMARC policies
OpsHelp services
CronDaily is the field notebook for OpsHelp — practical web ops for WordPress sites, server management, migrations, and security hardening.