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 Copy to put the URL on your clipboard, or Download 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.