Query Parameter Builder
Build a correctly encoded query string from key/value pairs and append it to a base URL, runs entirely in your browser.
About this tool
Add key/value rows and this tool assembles them into a properly percent-encoded query string, appended to an optional base URL. Values are encoded through the browser’s own URLSearchParams, the same mechanism used to build query strings in production code, so spaces, ampersands, and other reserved characters in a value never corrupt the result the way manual string concatenation would.
Useful for constructing a test link with several tracking or filter parameters, building a webhook or API callback URL by hand, or checking exactly how a given set of parameters will be encoded before hardcoding it somewhere. If the base URL already has a query string, new parameters are appended with "&" rather than overwriting it.
Frequently asked questions
- What happens if I leave the base URL blank?
- You get back a bare query string starting with "?", which you can append to whatever URL you are working with elsewhere. This is useful when you only care about the encoded parameter portion.
- Can I add the same key more than once?
- Yes. Adding two rows with the same key produces a repeated parameter (e.g. "tag=a&tag=b"), which many APIs and frameworks use to represent an array value for a single field.
- Why not just type the query string by hand?
- Hand-typed query strings are the most common source of subtly broken links: an un-encoded space, ampersand, or plus sign inside a value silently truncates or splits the parameter for the receiving server. Building it through URLSearchParams guarantees every value is escaped correctly.
- Is my data sent anywhere?
- No. The query string is assembled entirely in your browser with no network request involved.
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