What Is Incremental Crawling?

TL;DR

Incremental crawling is re-crawling a site to capture only what changed since the last run, instead of fetching every page again. The crawler tracks which pages it has seen and how often they change, then recrawls new and updated pages while skipping unchanged ones, saving time, bandwidth, and load on the target.

The Problem It Solves

The first crawl of a site is a full crawl: you have nothing, so you fetch everything. The second crawl is different. Most pages have not changed, and refetching all of them wastes crawl budget and hammers the site for no new data. Incremental crawling asks a sharper question: what is new or different since last time, and fetches only that.

How Change Gets Detected

A crawler decides what to recrawl using cheap signals before committing to a full fetch:

HTTP validators. Last-Modified and ETag headers, checked with a conditional request, let the server answer 304 Not Modified so you skip unchanged pages.
Sitemap lastmod. A sitemap's <lastmod> dates flag which URLs changed.
Content hashing. Storing a hash of each page's meaningful content detects real changes and ignores cosmetic ones.
Change frequency. Pages that historically change often (a news feed) get recrawled more than static ones (an about page).

Incremental Crawling and Monitoring

Incremental crawling is the foundation of change monitoring. Once you can cheaply tell what changed, you can turn that into events: a price moved, a job post appeared, a policy page was edited. This overlaps with change tracking, which is incremental crawling applied to watching specific pages over time.

Key Takeaways

Incremental crawling refetches only new or changed pages, not the whole site.
Change is detected via ETag/Last-Modified, sitemap dates, and content hashing.
It underpins change monitoring: cheap change detection becomes actionable events.

How ScrapeGraphAI Handles This

ScrapeGraphAI's monitor service applies incremental principles to watch pages on a schedule and report only when content changes, so you consume updates rather than recrawling everything yourself.