Guides
The complete, plain-English knowledge base behind our tools — how search engines and AI systems read your site, how email actually reaches the inbox, and how to make everything fast and secure. Every guide ends with the free tool to check your own site.
16 guides across 6 topics.
AI readiness & GEO
- Generative Engine Optimization (GEO): how to get cited by AI3 minGEO is SEO for AI answers. Learn how ChatGPT, Claude, Perplexity and Google's AI Overviews decide what to cite — and the concrete steps to get your brand into the answer.
- What is llms.txt and how to write one2 minllms.txt is a simple Markdown file that points AI systems at your most important content. Here's what it is, what goes in it, and how to publish a valid one.
- Why AI can't read your page — and how server-side rendering fixes it2 minIf your content only appears after JavaScript runs, crawlers and LLM fetchers see an empty shell. Here's why, and how SSR/SSG fixes it.
- How to control AI crawlers (GPTBot, ClaudeBot and more)2 minAllow or block AI crawlers deliberately. Here's what each bot does, how to set an explicit robots.txt policy, and how to verify it's actually working.
Email & deliverability
- Email deliverability: the complete guide to reaching the inbox2 minWhy your mail lands in spam and how to fix it. A complete, plain-English guide to SPF, DKIM, DMARC, alignment, MTA-STS and the reputation factors that decide the inbox.
- How to fix multiple SPF records (and the 10-lookup limit)2 minTwo SPF records break SPF for all your mail. Here's how to merge them into one valid record and stay under the 10-lookup limit.
- How to set up DMARC (from p=none to p=reject)2 minDMARC tells receivers what to do when SPF/DKIM fail — and gives you reports on who's sending as you. Here's how to roll it out safely from p=none to p=reject.
- How to set up DKIM (selectors, keys and rotation)2 minDKIM cryptographically signs your mail so receivers can verify it wasn't forged or altered. Here's how selectors and keys work, and how to publish them correctly.
SEO & structured data
- How to add structured data (JSON-LD)2 minStructured data helps search engines and AI systems understand your pages. Here's how to add valid JSON-LD that matches your visible content and earns rich results.
- Open Graph & Twitter Cards: make your links look great when shared2 minA missing og:image can halve your click-through. Here's how Open Graph and Twitter Card tags work, the exact set to add, and how to preview them before you ship.
Security & HTTPS
- How to add HTTP security headers (HSTS, CSP and more)2 minA practical guide to the HTTP security headers every site should send — what each one does, safe values to start with, and how to roll them out without breaking things.
- Content-Security-Policy explained (with a safe rollout)2 minCSP is the strongest defence against XSS — and the easiest header to get wrong. Here's how it works, a safe starting policy, and how to reach a strict nonce-based CSP.
- How to fix common SSL/TLS certificate errors2 minExpired, untrusted or mismatched certificates throw scary browser warnings that kill trust. Here's how to diagnose and fix the most common SSL/TLS errors.
DNS & domains
- DNS records explained: A, AAAA, CNAME, MX, TXT, NS and more2 minA plain-English reference to every DNS record type that matters — what each does, when to use it, and the mistakes that take sites and email offline.
- What is DNSSEC and how to enable it2 minDNSSEC cryptographically signs your DNS so answers can't be forged. Here's what it protects against, how it works, and the two-step process to enable it safely.
Performance
Prefer to just scan your site?
Run the full Domain Audit or browse all tools — each finding links back to the guide that fixes it.