Vercel + MERJ July 2024 rendering study — analyzed 100,000+ Googlebot fetches; 100% HTML pages rendered; median delay 10s, p75 26s, p90 ~3h, p95 ~6h, p99 ~18h; VENDOR INCENTIVE FLAGGED + high-authority test sites

Claim: The most-cited independent rendering dataset is the July 2024 Vercel + MERJ study ("How Google handles JavaScript throughout the indexing process"), which analyzed over 100,000 Googlebot fetches (with ~37,000 render beacons matched against server logs on nextjs.org, monogram.io and basement.io, April 1–30, 2024, using MERJ's Web Rendering Monitor + Edge Middleware).

Headline findings:

• "Successfully rendered 100% of HTML pages, including those with complex JavaScript."
• "No significant difference in rendering success rate based on JavaScript complexity."
• Rendering delay distribution: median 10 seconds, 75th percentile 26 seconds, 90th percentile ~3 hours, 95th ~6 hours, 99th ~18 hours. (25th percentile rendered within the first 4 seconds.)

This is strong evidence that Google can render JS well.

Source: Vercel + MERJ, July 2024 ("How Google handles JavaScript throughout the indexing process").

Confidence: Medium-high. Methodology disclosed, results published.

Caveat: Quarantined vendor figure. Three decisive caveats:

1. Commercial incentive — Vercel sells Next.js hosting/frontend cloud; the conclusion supports the business case; the primary test site is Vercel's own nextjs.org; a co-author is Vercel's CTO.
2. Survivorship / selection bias — every test site (nextjs.org, monogram.io, basement.io) is an established, high-authority, heavily-linked property. The study does not test new or low-authority domains. The rosy medians plausibly reflect crawl/render priority Google grants important sites.
3. Even Vercel's own data rates CSR "Poor" on crawl efficiency and warns "might not be indexed if rendering fails."

For the contrasting zero-authority datapoint see Onely November 2022 experiment (Ziemek Bućko) — brand-new zero-authority test subdomain; JS-folder page 7 took 313 HOURS vs HTML 36 hours (9x slower); first link 52h vs 25h — different stage (discovery, not render) but the high-authority/low-authority contrast is the point. For the new-site verdict see Google CONDITIONAL gate — critical content locked behind client-side JS gates indexing for new low-authority sites; high-authority sites are largely fine; the bite is concentrated where it hurts most and Rule: SSR or SSG is the DEFAULT for any content that must be indexed; CSR for indexable content is a GAMBLE whose downside lands hardest on new low-authority sites.