Query String Builder
Build URL query strings from key/value pairs with automatic percent-encoding — live output as you type. Free, in-browser.
100% Private — Runs entirely in browserInstant calculation & resultFree, no sign-up
Query String Builder — Live • Auto-encoding
Hand-writing query strings is a classic source of subtle bugs — forgotten ampersands, unencoded spaces, broken UTF-8. Add key/value pairs in a simple table and get a correctly percent-encoded URL, updated live as you type.
How to use this tool
- Optionally enter a base URL (or build just the query string).
- Add parameters — a new empty row appears automatically.
- Copy the live result; toggle encoding off only if your values are pre-encoded.
Encoding uses the standard encodeURIComponent rules, so spaces, ampersands, equals signs, and non-ASCII characters in your values can't break the URL structure.
If the base URL already contains a ?, additional parameters are appended with & — so you can safely extend existing links, like adding UTM tags to a campaign URL.
Frequently Asked Questions
When should I turn encoding off?
Only when your values are already percent-encoded — encoding twice turns %20 into %2520. For raw human-typed values, leave it on.Is my code uploaded to a server?
No. Everything runs locally in your browser — the code or text you paste never leaves your device. You can even use the tool offline once the page has loaded.Is there a size or usage limit?
No accounts, no daily quotas, no paywalls. Very large inputs are only limited by your device's memory.