I'm building a search index from many websites, what crawler should I use?

If your goal is to build a search index from many websites, the “best” crawler depends mostly on scale, freshness needs, and how much control you want over extraction and politeness.

Good options by use case

1. Large-scale, production crawl

• Apache Nutch
  Good if you want an open-source, distributed crawler that can feed a search pipeline. It’s a classic choice for building web indexes.
• Heritrix
  Excellent for large, archive-style crawling, especially if you care about broad coverage and standards compliance. Less “search pipeline” oriented than Nutch.

2. Flexible crawling + extraction

• Scrapy
  Great if you want a Python-based framework and more control over rules, parsing, retries, and data extraction. Best for targeted or mid-scale crawling, not massive web-scale by itself.
• Playwright / Puppeteer + custom crawler logic
  Use this if many sites are heavily JavaScript-rendered. It’s more expensive than plain HTTP crawling, so usually only for pages that need it.

3. Managed / cloud-based

• Common Crawl data
  If you don’t need to crawl yourself, this is often the cheapest way to get a huge web corpus to index.
• Commercial crawling platforms
  Useful if you want less ops work and more reliability, but costs can add up.

My practical recommendation

For a search index across many websites:

• Start with Scrapy if you’re building a custom system and don’t need web-scale immediately.
• Move to Nutch or a distributed architecture if you need large-scale crawling.
• Add Playwright only for JS-heavy sites.

Important features you’ll want

No matter what crawler you choose, make sure it supports:

• robots.txt compliance
• polite rate limiting
• canonical URL handling
• duplicate detection
• incremental recrawling / change detection
• content extraction and metadata capture
• sitemaps and feed ingestion
• blocked/allowed domain rules

One more note

If you’re indexing third-party websites, be careful about:

• legal/terms-of-service restrictions
• copyright/content reuse rules
• request load on target sites

If you want, I can recommend a crawler based on:

1. estimated number of pages,
2. whether sites are JS-heavy, and
3. whether you want open-source only or are open to managed tools.