Tools
Query string parser & builder
Paste a URL or a raw query string to break it into editable key-value parameters. Repeated keys are preserved, percent-encoded values are decoded so you can read them, and the encoded query string rebuilds live as you edit. Everything runs client-side: your URL never leaves this tab, and nothing is uploaded or stored.
Reading and building query strings
A query string is the part of a URL after the ?: a set of key=value pairs joined by &. It is how the browser passes state to a server: search terms, pagination, filters, UTM campaign tags, feature flags, and more. Because values are percent-encoded, a real-world query string is often hard to read at a glance: spaces show up as + or %20, and symbols become escape sequences like %2F.
This tool decodes each value into plain text, lays the parameters out in a table, and re-encodes correctly when you change something. It is handy for debugging a broken redirect, tweaking an API request, constructing tracking links, or just understanding what a long URL from a log actually contains. Duplicate keys (the usual shape of array or multi-select parameters) are kept distinct so you never lose information in a round-trip.
Parsing and encoding use the browser's built-in URL and URLSearchParams APIs, the same primitives your application code relies on, so the output matches what your runtime will produce.
Frequently asked questions
- What does this query string parser do?
- It splits a URL or query string into its individual key-value parameters, decodes the percent-encoding so values are human-readable, and lets you edit, add, or remove them in a table. As you edit, it rebuilds a correctly encoded query string you can copy back into your app.
- How are repeated keys handled?
- Keys that appear more than once (like tag=a&tag=b) are common for multi-select filters and array parameters. They are kept as separate rows in original order, never merged or deduplicated, so the rebuilt string preserves the exact multiplicity your backend expects.
- Why do spaces become a plus sign when I rebuild?
- The tool encodes with the application/x-www-form-urlencoded rules used by URLSearchParams, where a space is written as +. Both + and %20 decode back to a space in a query string, so either form is valid. Reserved characters such as &, =, and # are percent-encoded so they cannot break the string.
- Does my URL or data get sent anywhere?
- No. Parsing, editing, and rebuilding all run locally in your browser using the native URL and URLSearchParams APIs. There are no network requests and nothing is uploaded, logged, or stored, so it is safe for URLs that contain tokens or internal parameters.
- Can I paste a full URL, not just the query part?
- Yes. Paste a complete URL and the tool separates the origin and path from the query automatically, then offers both the rebuilt query string and the full rebuilt URL. A hash fragment is dropped since it is not part of the query.