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Query String Builder

Build and edit URL query strings without breaking the encoding.

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Paste a URL that already has parameters and they are loaded into the box above.

Quick Tool Overview

The Query String Builder assembles a URL from key and value pairs with correct percent-encoding, and works in reverse too — paste a URL and edit any parameter as a row.

What it does
Builds and edits URL query strings
You give it
Key and value pairs, or an existing URL
You get back
A correctly encoded URL
Best for
Tracking links, API test URLs and campaign parameters
Developer Tools Free, unlimited use No sign-up Runs in your browser

About the Query String Builder

Assembling a URL by hand is how encoding bugs happen: an ampersand inside a value splits the parameter, a space becomes a broken link, a hash truncates everything after it. This builds the query string properly, one key and value pair at a time.

It also works in reverse. Paste an existing URL and every parameter becomes an editable row, so you can change one value in a long tracking link without counting ampersands. Duplicate keys are preserved rather than collapsed, since some APIs use them as arrays. The finished URL is shown with its length, because browsers and servers start truncating somewhere around two thousand characters and there is no error when they do.

Key features of the Query String Builder

Edits an existing URL

Paste one and every parameter becomes a row, so changing one value in a long tracking link does not mean counting ampersands.

Encoding handled

Ampersands, spaces and hashes inside values are escaped, which is where hand-assembled URLs break.

Duplicate keys preserved

Some APIs use a repeated key as a list, so they are kept rather than collapsed.

Length warning

The total is shown, with a warning past the point where browsers and proxies start truncating without any error.

Rows can be disabled

Turn a parameter off without deleting it, which is how you test whether it is the one causing a problem.

How to use the Query String Builder

  1. 1

    Set the base URL

    Or paste a full URL and its existing parameters are loaded as rows.

  2. 2

    Add or edit parameters

    One key and value per row, encoded correctly as you type.

  3. 3

    Watch the length

    The total is shown, with a warning past the point where truncation starts.

  4. 4

    Copy the URL

    The complete address, ready to use.

Frequently asked questions

Anything outside letters, digits and a few safe symbols. The critical ones are the space, the ampersand, the equals sign and the hash — each of which changes the meaning of the URL if left raw.

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