Query String Builder

How to use Query String Builder

1. Open Query String Builder — it runs entirely in your browser with no setup.
2. Paste or type your input into the text area, or upload a file where supported.
3. Set any options you need. The result appears in the output panel — there is no upload step and no waiting on a server.
4. Review the output instantly; large inputs are handled locally without lag.
5. Copy the result to your clipboard or download it. Your data never leaves the page.

Why use Query String Builder?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full developer tools suite, so related query string builder tasks are one click away.

What people use Query String Builder for

• Assembling an API request URL with correctly encoded parameters.
• Building a campaign link with UTM parameters without typos.
• Constructing a test URL with values that contain spaces or symbols.

Query String Builder: limits and things worth knowing

• Each value is encoded with the equivalent of encodeURIComponent, which escapes & = ? and # — the characters that would otherwise break the URL structure. encodeURI does not escape these and is the wrong function for a parameter value.
• Spaces are encoded as %20 rather than +. Both are accepted by essentially every server, but %20 is correct in the general URI syntax while + is form-encoding specific.
• The order of parameters usually does not matter to a server, but it does matter to a cache key and to any request signature computed over the string.
• Browsers and servers impose practical URL length limits around 2,000 to 8,000 characters. A large payload belongs in a request body.

Is it private and secure?

Your privacy is built in. Query String Builder runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Is It Safe to Paste Production Data Into Online Tools? — JWTs, API responses and env files get pasted into online formatters every day. Here's what actually happens to that data and how to check before you paste.