What is a Spider?
A spider (or web crawler) is an automated agent that discovers URLs, downloads pages, and sends them to an indexer. Spiders can be external (Googlebot, Bingbot) or internal (your site-search/crawl jobs for documentation, PDPs, guides).
How It Works (quick)
- Seeds → frontier: Start from seed URLs (sitemaps, links), maintain a priority queue.
- Fetch & render: Respect robots.txt and meta robots; fetch HTML; render JS if allowed/needed.
- Parse & extract: Follow links, canonical/hreflang, structured data; capture last-modified.
- De-duplicate: Normalize URLs (params, fragments); detect near-duplicates.
- Rate & budget: Throttle per host; schedule revisits by change rate.
Why It Matters in E-commerce
- SEO: Ensures PDPs, categories, and content are discoverable and refreshed.
- Site search: Internal spiders feed help centers, blog, and spec sheets into your index.
- Governance: Prevents crawl bloat from facets/params and stale variants.
Best Practices
- Sitemap hygiene: XML sitemaps with canonical, 200, indexable URLs; keep
lastmod accurate. - Robots control: Block infinite facets, duplicates; allow core landing pages.
- Canonical & hreflang: Point variants to a single canonical; declare locales.
- JS & SPA: Prefer SSR/ISR for crawlable content; avoid blocking resources.
- Parameters: Whitelist a few SEO-worthy params; add noindex to the rest.
- Performance: Fast 2xx responses; stable 301s; use 410 for permanent removals.
Challenges
- Faceted URL explosions, JS-only content, soft 404s, and inconsistent canonicals.
Examples
- Category filters generate
?size=45&color=black: blocked from indexing, but still crawlable for UX. - Internal crawler ingests returns policy pages to power answers.
Summary
Spiders make discovery possible. Give them clean sitemaps, strong canonicals, and safe parameter rules so the right pages get crawled and indexed quickly.
