Query Strings

What is a Query String?

A query string is a key=value parameter list appended to a URL (e.g., ?size=45&color=black&sort=price_asc&page=2). It encodes filters, facets, sorts, pagination, tracking, and sometimes search terms (when not using path-based routes).

How It Works (quick)

• Encoding: Keys/values are URL-encoded; arrays or repeated keys represent multi-select facets.
• Parsing: Server or client reads params and applies filters/sorts; updates URL on changes.
• State & sharing: The URL becomes a shareable bookmark of the current view.
• SEO controls: Canonicals, parameter handling rules, and noindex for infinite combos.

Why It Matters in E-commerce

• UX: Persistent state enables sharable filtered collections and back/forward navigation.
• Analytics: Parameters clarify user intent and campaign attribution.
• Performance: Parameterized APIs enable caching for popular combos.

Best Practices

• Human-safe keys: size, brand, price_min/price_max, in_stock=true.
• Canonicalization: One canonical per collection; whitelist a small set of SEO-worthy params; add noindex to the rest.
• Sorting & paging: Include sort and page parameters; keep page size bounded.
• Security: Sanitize inputs; ignore unknown params; don’t expose secrets in URLs.
• Privacy: Avoid PII in query strings; use short-lived tokens for sessions.
• UTM hygiene: Strip or consolidate tracking params when generating internal links.

Challenges

• Crawl bloat from facet permutations; duplicate content; long URLs; locale/unit differences.

Examples

• /men/trail-running?size=45&waterproof=true&price_min=80&price_max=150&sort=rating_desc
• /search?q=air+max+270&in_stock=true&page=1

Summary

Query strings carry the state of your collections and search. Keep keys clean, sanitize inputs, and control crawl space with canonicals and parameter rules.