Introducing the Query String Builder — Build & Decode URL Parameters

Hand-crafting a URL query string is easy to get wrong — an unencoded space breaks the URL, a forgotten & merges two parameters, and a duplicated key silently overwrites data. The new Query String Builder takes care of all of this automatically.

Two modes in one tool

Build mode — add your key-value pairs, optionally set a base URL, and the tool assembles a correctly percent-encoded query string and full URL ready to copy.

Parse mode — paste any URL or raw query string and see every parameter decoded into a clean table, with the raw encoded value alongside the human-readable decoded value.

What makes it useful

• Correct encoding out of the box — RFC-3986 (%20 spaces) or form-encoded (+ spaces), your choice.
• Duplicate-key warnings — the tool flags repeated keys so you can decide if it’s intentional.
• Full encoding table — see exactly what each key and value look like encoded, which is essential for debugging API requests.
• One-click copy — copy the query string, the full URL, or the normalised rebuilt query string from the parser.
• 100% in-browser — no server, nothing uploaded, works offline.

Built for developers

Whether you’re constructing a REST API request, debugging a broken URL from browser DevTools, building search links, or passing complex filter parameters — the Query String Builder gives you confidence that every character is encoded correctly.

Read the full guide: URL Query Strings Explained.