Free Query String Parser Online
Parse URL query strings into key-value pairs and back — decode, inspect, and build query parameters in your browser.
How it works
Paste query string
Paste the query string (with or without the leading ?) into the input.
Parse
Click Parse or press Enter. Each parameter is decoded and listed as a key-value pair.
Inspect values
See every parameter decoded, including percent-encoded characters and repeated keys.
Build query string
Edit key-value pairs and click Build to generate the encoded query string.
Common use cases
Debugging API requests
Parse the query string from a logged API request to read all the parameters without manually decoding percent-encoding.
Analytics URL inspection
Marketing tracking URLs (UTM parameters) can be long and confusing. Parse them to list each utm_source, utm_medium, utm_campaign value.
OAuth parameter checking
Parse OAuth callback URLs to inspect the code, state, scope, and error parameters returned by the authorization server.
Form submission debugging
GET form submissions append field values as query parameters. Parse them to see what data your form is sending.
Frequently asked questions
Should I include the ? in the input?
Both work — the parser strips a leading ? automatically. You can paste the full URL or just the query string portion.
What about repeated keys (arrays)?
Multiple values for the same key (e.g., tag=a&tag=b) are shown as separate rows. URLSearchParams handles this natively.
Are values automatically decoded?
Yes — percent-encoded values (%20, %2F, etc.) and + signs used as spaces are decoded to their plain-text form.
Is my data sent to a server?
No. The parser uses URLSearchParams — a native browser API. Everything runs locally.