How are repeated keys handled?

a=1&a=2 becomes { "a": ["1", "2"] }. That matches how most form parsers treat duplicates.

What about user[name]=Ada?

Bracket paths become nested objects. user[name]=Ada&user[id]=7 is { user: { name, id } }.

Is this encodeURIComponent?

The builder encodes keys and values. The parser decodes + as space. Use the URL encode page for a single value.

Runs in your browser · Last updated 7 September 2026

Free Query String Builder and Parser

Free query string builder and parser. Turn ?a=1&a=2 into JSON (arrays and a[b] nests) or build a URL from pairs. Browser tool — nothing is uploaded.

URL or query string

Parsed JSON

{
  "q": "hello world",
  "tag": [
    "a",
    "b"
  ],
  "user": {
    "name": "Ada"
  }
}

Base URL (optional)

Built URL

https://example.com/search?q=hello%20world&utm_source=newsletter

How to use this tool

Paste a URL or ?query to parse it to JSON.
Or type key/value pairs and an optional base URL.
Copy the JSON or the built URL.

Worked example

https://example.com/search?q=hello+world&tag=a&tag=b#top parses to q = “hello world” and tag = [“a”, “b”]. Building utm_source=news and q=a&b on that origin encodes the ampersand so the query does not split.

Frequently asked questions

How are repeated keys handled?: a=1&a=2 becomes { "a": ["1", "2"] }. That matches how most form parsers treat duplicates.
What about user[name]=Ada?: Bracket paths become nested objects. user[name]=Ada&user[id]=7 is { user: { name, id } }.
Is this encodeURIComponent?: The builder encodes keys and values. The parser decodes + as space. Use the URL encode page for a single value.
Uploaded?: No.