JSON, Data & Formatter Tools

Free Query String Parser and Builder

A browser-based query string tool with two modes: Parse mode extracts and displays all query parameters from a URL or query string in a clean table, with duplicate detection. Build mode constructs a query string from key=value pairs entered line by line. Both modes support alphabetical sorting of parameters.

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What is Query String Parser and Builder?

quickAnswer

Parse a URL's query string into a key-value table with duplicate detection, or build a query string from parameter pairs. UTM-friendly with sorting options.

Last updated: 2026-06-05

limitations

Does not deeply parse nested query string formats like PHP-style arrays (?a[b]=c) — parameters are treated as flat key-value pairs.
Very long URLs (over 10KB) may have many parameters and the table may become scroll-heavy.
The builder does not validate parameter names against any standard — any string is accepted as a key.

Sources:MDN Web Docs · W3C Specifications · jquery.app on GitHub

How to use this tool

Choose Parse mode to extract parameters from a URL, or Build mode to construct a query string.
Paste your URL or enter key=value pairs (one per line for build mode).
Review the extracted parameters or toggle sort and dedup options.
Copy the result for use in your application.

What you can use it for

Parse a UTM-tagged URL to see all marketing parameters (utm_source, utm_medium, utm_campaign) in a readable table.
Build a query string for an API request by entering key=value pairs and getting a properly encoded query string.
Detect duplicate query parameters in a URL that might cause unexpected behavior in your application.

Use cases

Practical examples

example

Analyze marketing UTM parameters

A marketer pastes a long URL with UTM parameters. The parser extracts utm_source=google, utm_medium=cpc, and utm_campaign=launch into a clean table, making it easy to verify the tracking setup.

example

Build an API query string

A developer needs to construct a query string for a REST API call. They enter filter=active, page=1, and limit=20 as key=value pairs. The builder outputs 'filter=active&page=1&limit=20' ready to append to the API URL.

Common mistakes

Forgetting that query string keys are case-sensitive — filter=active and Filter=active are different parameters.
Not encoding special characters in parameter values before building — the builder encodes automatically, but manual construction can miss this.
Assuming duplicate parameters are an error — some APIs intentionally use duplicate keys for multi-value parameters.

verification

Paste a URL with query parameters and verify all parameters are extracted into the table with correct keys and values.
Switch to Build mode, enter 3 key=value pairs, and verify the output is a properly formatted query string.

FAQ

Questions about Query String Parser and Builder

How are duplicate query parameters handled?

The parser detects and warns about duplicate parameter names, showing which keys appear more than once. The builder does not prevent duplicates since some APIs intentionally use them (e.g., ?tag=a&tag=b). If you want unique keys, enable sort mode and remove duplicates manually.

Does this tool handle URL fragments (hash)?

The parser strips the URL fragment (#section) before processing because fragments are not sent to the server and are not part of the query string. The fragment content is handled client-side only.

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