Definition
URL normalization (also called URL canonicalization) is the process of converting web addresses into a standardized, consistent format. Multiple different URLs can point to the same page content, and without normalization, a crawler may visit the same page repeatedly under different URL variations, wasting resources and producing duplicate data.
Common URL Variations
The following URLs may all serve identical content:
https://example.com/productshttps://example.com/products/https://www.example.com/productshttps://EXAMPLE.COM/productshttps://example.com/products?ref=homepagehttps://example.com/products#sectionhttps://example.com/products/index.html
Without normalization, a crawler treats each as a distinct page to visit.
Normalization Rules
Standard Transformations
- Lowercase the scheme and host —
HTTPS://EXAMPLE.COMbecomeshttps://example.com - Remove default ports —
:443for HTTPS,:80for HTTP - Remove trailing slashes —
/products/becomes/products(or consistently add them) - Remove fragment identifiers —
#sectionis stripped since fragments are client-side only - Sort query parameters —
?b=2&a=1becomes?a=1&b=2 - Remove tracking parameters — strip
utm_source,ref,fbclid, and similar tracking tags - Decode unnecessary percent-encoding —
%7Ebecomes~
Site-Specific Normalization
Some normalizations depend on the specific site: whether www and non-www serve the same content, whether certain query parameters affect page content, and whether trailing slashes are significant.
Why It Matters for Crawling
Effective URL normalization prevents a crawler from wasting budget on duplicate pages, ensures deduplication in the resulting dataset, and provides cleaner URL references in the extracted data. For large-scale crawls, the efficiency gain is substantial.
URL Normalization in ScrapeGraphAI
ScrapeGraphAI applies URL normalization during crawl operations to prevent duplicate page visits. URLs are standardized before being added to the crawl queue, ensuring each unique page is visited exactly once.