Free browser tool

Query string builder

Build and parse URL query strings from key-value pairs.

Input and settings

How to use it

Start with an absolute URL and add or replace query parameters from one key=value line per parameter.

Enter a base URL such as https://example.com/.
Enter parameters one per line in key=value form.
Select Build to generate the final URL.

Base URL: Absolute URL parsed by URL()
Parameter format: One key=value pair per line
Existing query: Preserved unless the same key is set again
Repeated key in input: Later set replaces the earlier value

Adding utm_source keeps unrelated parameters

https://example.com/?ref=home plus utm_source=newsletter becomes a URL containing both ref=home and utm_source=newsletter.

A nonblank line without = is ignored by the current builder. If you intended to add a parameter, check the generated URL before copying it.

Special characters are encoded automatically

Spaces and other characters that cannot appear raw in a query string are converted to URL-safe form in the generated URL.

Entering the same key replaces its current value

If the base URL already contains a parameter and you add that key again, the generated URL keeps the new value for that key. This builder is aimed at one value per key.

Empty values are allowed when the equals sign is present

A line like preview= creates a parameter with an empty value.

Fragments stay separate from the query

If the base URL contains #section, query parameters are managed before the fragment according to normal URL serialization rules.