---
title: "Query String Parser - Decode & Rebuild URLs | CanDoYa"
description: "Free query string parser. Decode URL parameters, keep duplicate keys, edit values, and rebuild a query string or full URL in your browser."
url: https://candoya.com/tools/query-string-parser/
locale: en
type: browser-tool
---

# Query String Parser

Category: Developer

## What is a query string parser?

A query string parser turns the part of a URL after the question mark into readable key/value rows. Paste a raw query string or a full URL to decode percent-encoded text, keep duplicate keys in order, edit parameters, and rebuild a clean query string or updated URL.

Everything runs in your browser, so private links, API callbacks, campaign URLs, and temporary tokens are not uploaded. The parser uses the browser's standard `URL` and `URLSearchParams` APIs, then adds an editable table on top so you can inspect and rebuild parameters without losing repeated keys.

## How to use it

1. **Paste a URL or query string** - Use a full URL like `https://example.com/?a=1`, a raw query like `a=1&b=2`, or a query with a leading question mark.
2. **Review decoded rows** - The table shows each key and value after percent decoding. Duplicate keys stay as separate rows in their original order.
3. **Edit, add, remove, or sort** - Change keys and values directly, add missing parameters, remove noisy rows, or sort the list by key when you want a stable output.
4. **Copy the rebuilt output** - Copy the encoded query string, the version with a leading question mark, the updated full URL, or a JSON array of key/value pairs.

## Who it's for

- **Developers debugging callbacks** can paste OAuth, webhook, or redirect URLs and inspect every decoded parameter row.
- **Marketers checking campaign links** can read `utm_*` values, spot blanks, and rebuild a clean tracking URL.
- **QA teams reproducing bugs** can edit one parameter at a time and copy the updated query string into a test case.
- **Support teams handling shared links** can see duplicate keys and blank values that are easy to miss in a long URL.

## Expert note

A query parser should not collapse repeated keys: `tag=shoes&tag=sale` is different from one `tag` value joined with a comma, and many APIs read every occurrence with `getAll()`. This tool keeps the order intact and uses form-url-encoded rules, so spaces serialize as `+` and literal plus signs serialize as `%2B`.

## Frequently asked questions

### Is this query string parser free?

Yes. It is free to use with no sign-up, no download, and no usage limit. Paste a query string or URL and the decoded rows appear immediately in your browser.

### Is my URL or query string uploaded?

No. Parsing, editing, and rebuilding all happen locally in your browser. That is useful when a URL contains access tokens, email addresses, campaign IDs, or other values you do not want to send to another server.

### Can it parse a full URL?

Yes. Paste a full URL and the tool reads only the URL's search parameters, preserves the path and fragment, and gives you a rebuilt full URL after edits. You can also paste a raw query string with or without the leading question mark.

### Does it keep duplicate keys?

Yes. Duplicate keys are preserved as separate rows in the order they appear. The duplicate summary calls them out so you can see cases like `tag=shoes&tag=summer` without accidentally merging them.

### How are blank values handled?

Blank values stay blank. A parameter such as `empty=` appears with an empty value, and a key without an equals sign is treated the same way by `URLSearchParams` when it is rebuilt.

### Are percent-encoded values decoded?

Yes. Values like `blue%20shoes` show as `blue shoes` in the table. When you copy the rebuilt query, the tool encodes values again using browser-standard form-url-encoded rules.

### What happens to the part after #?

In a full URL, the fragment after `#` is preserved when the rebuilt URL is copied. In a raw query string, anything after `#` is ignored because fragments are not part of the query parameters.

## Related tools

- [URL Parser](https://candoya.com/tools/url-parser/)
- [URL Encode and Decode](https://candoya.com/tools/url-encode-decode/)
- [JSON Formatter](https://candoya.com/tools/json-formatter/)
- [Base64 Encode and Decode](https://candoya.com/tools/base64-encode-decode/)
- [JWT Generator](https://candoya.com/tools/jwt-generator/)

---

*Markdown edition of <https://candoya.com/tools/query-string-parser/>, published for AI agents and other automated readers. Index of key pages: <https://candoya.com/llms.txt>.*