Add key/value rows and instantly get a correctly percent-encoded query string, built with URLSearchParams. Enter a base URL to see the full assembled URL, or switch to Parse and paste an existing query string or URL to break each parameter down into a table.
Query strings often contain non-ASCII characters, spaces, and special characters like `&`, `=`, and `#`. Concatenating these by hand easily leads to bugs β missing encoding, double-encoding, or delimiter collisions. URLSearchParams is a browser standard API that correctly percent-encodes each value per the application/x-www-form-urlencoded rules and safely joins them with `&`. This tool uses that exact logic to build its output.
Query strings like `category=IT&category=Dev`, where the same key repeats, are common for multi-select filters or array-style parameters. The Parse tab reads every entry in order via URLSearchParams.entries(), showing a separate table row for each value even when the key repeats β avoiding the common mistake of keeping only the first value and silently dropping the rest.
Paste a full URL into Parse and it correctly extracts only the part after `?` (and before any `#`) as the query string. Conversely, paste the result from Build back into Parse to verify the encoding is correct and every value round-trips back to its original form.