What crawl budget is
Crawl budget is the amount of crawling Google is willing to do on your site over a stretch of time. It is shaped by two things: crawl capacity, meaning how much your server can handle without slowing down, and crawl demand, meaning how much Google wants to crawl based on your site's popularity and how often it changes.
Google does not crawl every page of every site constantly. It allocates attention. For most sites that allocation is more than enough, but for very large sites it becomes a real constraint worth managing.
Which sites actually need to care
If your site has a few hundred pages, crawl budget is almost never your problem. Google will find and crawl everything without trouble, and you should spend your energy elsewhere.
Crawl budget becomes a concern on large sites, generally tens of thousands of URLs or more: big ecommerce catalogs, news archives, listing sites, and large programmatic page sets. On these, crawling spent on junk URLs is crawling not spent on the pages that earn revenue.
What wastes crawl budget
Faceted navigation that spins up endless filtered URL combinations is the classic offender. Session IDs and tracking parameters in URLs create infinite duplicates. Soft 404s, long redirect chains, and large numbers of low-value or duplicate pages all consume crawls that could go to pages that matter.
Every crawl Google spends on a useless URL is a crawl it does not spend on a new product page or a fresh article. On a large site that trade-off directly affects how quickly your important content gets indexed.
How to manage crawl budget
Keep your XML sitemap clean and limited to canonical, indexable URLs. Block low-value URL patterns in robots.txt, and use canonical tags to consolidate duplicates. Fix redirect chains and broken links. Improve server speed so Google can crawl more in the same window. Watch the Crawl Stats report in Search Console to see where Google is actually spending its time.