Query String Builder
Build URLs and query strings from key-value pairs instantly
Parameters
Output URL
Query String Builder Example
Enter key-value pairs and a base URL to get a properly encoded query string. Example output:
Click Sample above to load this example.
What Is a Query String?
A query string is the part of a URL after the ? character, containing key-value pairs separated by &. Special characters in values are percent-encoded per RFC 3986. For example, a space becomes %20 and & becomes %26. This tool uses the browser's URLSearchParams API to construct correctly encoded query strings.
How to Use This Tool
Enter Base URL & Parameters
Type or paste your base URL (e.g., https://api.example.com/search). Then add key-value pairs using the table. Use the checkbox to enable or disable individual parameters without deleting them.
See the Encoded URL
The right panel updates instantly with the fully percent-encoded URL. Spaces, ampersands, and other special characters in values are automatically encoded. Disabled parameters are excluded.
Copy or Download
Click <strong>Copy</strong> to put the URL on your clipboard, or <strong>Download</strong> to save it. To parse an existing URL into its parameters, use the URL Parser.
Frequently Asked Questions
What happens to special characters in values?
They are percent-encoded using URLSearchParams. Spaces become + in URLSearchParams output and %20 in strict RFC 3986 encoding. Both are correctly decoded by all browsers and server frameworks.
Can I have duplicate keys?
Yes. Add multiple rows with the same key name. This produces tag=foo&tag=bar, which is valid per spec and used for multi-value parameters in APIs and form submissions.