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Query string builder

Convert key-value pairs into a URL query string with proper encoding.

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Query string builder
A query string is the part of a URL that comes after the question mark, carrying data as key-value pairs separated by ampersands. This tool builds one from a simple line-by-line list: paste one parameter per line in either "key=value" or "key: value" format, and it instantly generates a complete, properly encoded query string ready to append to a URL. This is essential when you need to construct search queries, filter parameters, tracking codes or any data-driven URLs by hand.
The builder automatically URL-encodes both keys and values, replacing spaces with %20, ampersands with %26, equals signs with %3D and other special characters with their encoded equivalents. This prevents accidental parsing errors when parameters contain punctuation, spaces or symbols. Every unsafe character gets the percent-encoding treatment so your URL remains valid. Blank lines are skipped, so you can paste messy input and the tool will clean it up automatically, leaving you with a perfectly formatted query string.
A checkbox option lets you control whether the output includes the leading question mark (on by default, so the string is immediately usable in a URL). The live tally counts how many parameters you have built. Copy the result, download it as text, or send it to other tools. Everything runs entirely in your browser, so your input never leaves your device.
FAQ
What is a query string?
It is the part of a URL after the ? character that passes data to a web server. For example, in "https://example.com/search?q=cats&limit=10", the query string is "q=cats&limit=10", carrying two parameters: q and limit.
How are special characters encoded?
The tool uses URL encoding (also called percent encoding) where each unsafe character becomes a percent sign followed by its hexadecimal code. Spaces become %20, & becomes %26, and so on. This ensures the server correctly parses your parameters instead of mistaking punctuation for syntax.
Can I use both "key=value" and "key: value" formats?
Yes. The tool accepts both formats on the same input. It parses "=" first, then ":" if no "=" is found, so you can freely mix them in the same list.
Is my input uploaded anywhere?
No. The query string is built entirely in your browser and your data never leaves your device. It is safe to use with sensitive information.