How To Parse Query Strings

Anatomy of a query string

Three character classes need encoding in query values:

URLSearchParams — the modern API

The spec says nothing about repeating a key. In practice, three conventions are common:

Encoding rules in query strings

Bracket notation also expresses nested objects:

Repeated keys — the array convention

There is no official URL length limit in the HTTP spec, but practical ceilings matter.

Nested keys — PHP-style

Keep query strings under 2 KiB to be safe across all infrastructure. If you are anywhere close, move the data to a POST body.

URL length limits

Booleans in URLs are entirely convention. Pick a pattern:

Boolean conventions

Building query strings safely

Unicode, normalization, and collation

Common mistakes

Run the numbers