Crawling JavaScript sites: which crawler actually renders

Crawling JavaScript sites: which crawler actually renders
If your site is React/Vue, a non-rendering crawler lies to you. I tested three on the same JS-heavy SPA.

Screaming Frog (JS rendering on):
➕ Renders via headless Chromium, shows rendered vs raw HTML side by side — you see what content only appears after JS
➖ Rendering slows the crawl 4-5x and eats RAM; you'll feel it past 10k URLs

Sitebulb:
➕ Renders too, and flags content/links that only exist post-render as a specific hint
➖ Same speed tax as Frog

Non-rendering mode (any tool, JS off):
➖ Reports your JS-injected content and links as missing — a false alarm that wastes hours

The lesson: always run one rendered crawl on a JS site to compare against the raw crawl. The diff is your indexability risk.

Best for: Frog for the raw-vs-rendered diff, Sitebulb for the prioritized hint.

Pick this if your content loads via JS — turn rendering on and eat the speed hit. Skip rendering only if you've confirmed your HTML is server-side complete.

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