Lab notes
Writing about speed.
What actually slows websites down, what AI assistants can and can't read, and what we changed on our own site. Explained without the jargon. No listicles.
Every note is also served as markdown at its own .md address, and listed in /llms-full.txt.
Latest: AI agents, 6 min read
Can ChatGPT read your website? The JavaScript test
Most AI crawlers don't run JavaScript, so text your site builds with scripts can be invisible to them. How to check your pages in five minutes, and what fixes it.
12 Oct 2026. Read the note
All notes
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AI agents
12 Oct 2026
6 min read
Can ChatGPT read your website? The JavaScript test
Most AI crawlers don't run JavaScript, so text your site builds with scripts can be invisible to them. How to check your pages in five minutes, and what fixes it.
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Core Web Vitals
8 Oct 2026
8 min read
Website speed monitoring: what to watch, and how often
Why Google's own speed data reports a slowdown a week or more late, which free tools to check, and a simple routine that catches problems early.
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AI agents
8 Oct 2026
7 min read
AI crawlers in robots.txt: which to allow, which to block
GPTBot, OAI-SearchBot, ClaudeBot and the rest each do a different job. What blocking each one costs you, and three robots.txt policies you can copy.
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AI agents
7 Sept 2026
13 min read
What 'AI-ready' means for a website: nine dimensions, and where ours lands on each
AI readiness is not one thing. It's nine separate questions, from 'can an agent read this page' to 'can an agent buy from you'. What each one means, what this site has for each, and the ones it deliberately leaves empty.
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Core Web Vitals
14 Aug 2026
5 min read
What Google actually measures when it measures your site speed
Core Web Vitals explained in plain language: what LCP, INP and CLS really mean, the exact thresholds Google uses, and why a site can score 19 out of 100 and still load fine for real visitors.
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Case study
30 Jul 2026
8 min read
How this site scores 100/100 on PageSpeed: every decision explained
A line-by-line account of what makes sitespeedlabs.com load instantly: one self-hosted font, no framework runtime, inlined CSS, and none of our own JavaScript on any page. Including what we gave up to get there.
How does your site measure up?
Free check, plain-language results, no signup. Speed and what an AI assistant can read.