CrawlObserver vs DRKSpiderJava

CrawlObserver is a free private-beta SEO crawler available through web and API access. It reports more than 45 signals per page and describes audits without a page ceiling, including sites with 500K+ pages. Crawl comparisons identify added or removed URLs and changes to redirects, titles, and canonicals. Technical checks include redirect chains, internal PageRank, SimHash duplicate detection, and broken internal or external links. Internal authority-flow views help surface orphan pages, linking opportunities, and pages receiving too many links. JavaScript rendering can be off, automatic, or always enabled, with automatic detection for React, Vue, Next.js, and Nuxt. A REST API launches crawls and retrieves results. CrawlObserver says it follows robots.txt and crawl-delay, applies per-host delays, and blocks private IP ranges with post-DNS validation. Results are stored in ClickHouse.

DRKSpiderJava has no write-up on Specifiction yet; its figures are above.