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Crawling a site

Reach for crawlberg crawl when one URL is not enough — the user wants the docs site, the blog, the marketing pages, or the whole domain.

Quick recipe

crawlberg crawl https://example.com \
  --depth 3 \
  --max-pages 200 \
  --concurrent 8 \
  --rate-limit 250 \
  --stay-on-domain \
  --respect-robots-txt \
  --format markdown

Defaults you should usually override:

• --depth 2 is shallow — set it explicitly.
• --max-pages is unbounded by default; cap it for any unknown site.
• --concurrent 10 is aggressive for small hosts; drop to 4-8 for third-party sites.

Flag surface

Flag	Default	Purpose
--depth, -d	2	Maximum hop count from the seed URL.
--max-pages, -n	—	Hard cap on pages fetched. Set this on any unknown site.
--concurrent, -c	10	Parallel in-flight requests.
--rate-limit	200	Milliseconds between requests to the same origin.
--stay-on-domain	off	Skip links that leave the seed domain.
--respect-robots-txt	off	Honour robots.txt. Pass it for any third-party host.
--proxy	—	HTTP, HTTPS, or SOCKS5 proxy URL.
--user-agent	—	Override the request UA. Be honest.
--timeout	30000	Per-request timeout in ms.
--browser-mode	auto	auto, always, never — see the headless-fallback skill.
--browser-endpoint	—	External CDP ws:// URL.
--format	json	json or markdown.
--config	—	Inline JSON or @file.json for the full CrawlConfig.

Multiple seed URLs are accepted positionally — the engine fans out with batch_crawl and aggregates results.

When to pick which flags

Docs sites you own

crawlberg crawl https://docs.example.com \
  --depth 5 --max-pages 1000 --concurrent 16 --rate-limit 100 \
  --stay-on-domain --format markdown > docs.md

Higher concurrency and lower rate limits are fine on infrastructure you control.

Third-party sites

crawlberg crawl https://blog.unknown.example \
  --depth 2 --max-pages 50 --concurrent 4 --rate-limit 500 \
  --stay-on-domain --respect-robots-txt --format markdown

Stay shallow, cap pages, throttle hard, obey robots.

Multi-seed batch

crawlberg crawl \
  https://example.com/blog \
  https://example.com/docs \
  https://example.com/pricing \
  --depth 2 --max-pages 100 --stay-on-domain --format json

JSON output for a multi-seed crawl is a BatchCrawlResults object: { "results": [ { "url", "result", "error" }, … ], "total_count", "completed_count", "failed_count" }. Each entry's url is the seed URL, result is a full crawl payload (or null on failure), and error is a sibling string field (null on success). Iterate with .results[] | {url, error} — not a top-level array.

Output

Markdown mode

---
URL: https://example.com/page-one
---
# Page One

… markdown content …

---
URL: https://example.com/page-two
---
…

JSON mode

Top-level CrawlResult with pages: [...]. Each page carries the rendered Markdown plus metadata, links, images, JSON-LD, and HTTP response info. Read result.pages[i].markdown.content for the Markdown string.

Politeness checklist

• Pass --respect-robots-txt on every third-party crawl.
• Cap --max-pages — a runaway BFS can issue tens of thousands of requests.
• Bump --rate-limit for hosts that show signs of stress (5xx, slowdowns).
• Identify yourself via --user-agent crawlberg (contact@example.com).

Common pitfalls

• No pages returned. The seed page may be JS-only — the engine falls back to headless automatically in --browser-mode auto, but never mode will silently produce an empty crawl. Re-run with --browser-mode always or check the headless-fallback skill.
• Crawl leaves the domain. Pass --stay-on-domain. Combine with allow_subdomains: true in --config JSON to include subdomains.
• Slow crawl. The default rate limit is 200 ms per origin — multiple seed URLs on the same host still share the bucket. Spread seeds across hosts or raise --concurrent for unrelated origins.
• Memory growth. Each page carries full Markdown plus structured data. Stream JSON output to a file rather than holding it in memory; set --max-pages aggressively if downstream cannot keep up.

When to reach for map instead

If the user only needs the list of URLs (sitemap analysis, link planning, seeding another tool), use crawlberg map <url> — it skips rendering and returns a flat MapResult with hundreds of URLs in seconds.