Empirical research on what JavaScript content patterns deliver to bots and LLM fetchers in 2026. Open methodology, open data, reproducible findings.
Status: Phase 1 in progress. First findings expected June 2026.
Eight JavaScript content patterns × five page types × three rendering modes, crawled by all major bot classes. Per-cell signals captured in a public tracker.
Live test bed: next.jsseo.dev — 55 cells running now.
Raw bot tracker data, hypothesis pre-registration, methodology — all open from day one. CC0 / CC-BY for data, MIT for code.
Senior technical SEO consultant, 25 years in the field. Independent owner of SAWA PROJEKT, co-founder of FratreSEO.
In 15 days of JS SEO Lab data, the Next.js test bed saw 6,125 hits across 25 user-agent classes. GPTBot, Meta-external, Amazonbot, and three Google sub-bots together produced 862 hits with zero reques...
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Vercel and MERJ already settled that batch crawlers don't execute JavaScript. So why was I building a 6-mode renderability experiment? Here's why I rebuilt it as a pattern-axis instead — and what the ...
Vercel and MERJ established in 2024 that batch AI crawlers don't execute JavaScript. That's the rendering-mode answer. But real client audits don't ask "is this site SSR or CSR?" — they ask "is this specific JS pattern (a click-to-reveal, a useEffect-fetched price, a hash-routed navigation) costing me visibility in this specific bot's index?"
Eight JS content patterns (clean / js-images / js-links / click-reveal / js-fetched / hash-routing / late-loaded / mixed) × five page types × three rendering modes (SSR / CSR / optional SSG). Crawled by 25+ bot classes including GPTBot, ChatGPT-User, Claude-User, ClaudeBot, Googlebot, Bingbot, PerplexityBot.
Three-layer bot identification: reverse DNS for Google/Bing/Apple, IP-range CIDR matching against OpenAI/Perplexity published manifests, and explicit unresolved status for bot families without a reliable public verification path, including current Anthropic crawlers. False-positive UAs (deprecated anthropic-ai/Claude-Web) automatically flagged as unverified.