Query String Builder

Free Query String Builder

Compose URL query strings from named parameters with proper RFC 3986 encoding. Faster and safer than concatenating strings by hand, and great for API calls and tracking links.

Common Uses

• Build API request URLs
• Construct tracking links with UTMs
• Generate share URLs with prefilled state
• Test backend query parameter handling
• Demonstrate encoding rules to students

How It Works

We use the browser's URLSearchParams API to encode keys and values, then prepend your base URL with a single question mark. Duplicate keys are supported by appending instead of setting.

Privacy

Everything is built locally in your browser. No URLs are sent anywhere.

Related: URL Parser, URL Encoder/Decoder, MIME Type Lookup.

Related free tools

• XML Formatter & Minifier — Beautify or minify any XML — SOAP, RSS, SVG, sitemap. Browser-based parser.
• XML to JSON Converter — Parse any well-formed XML into a clean JSON tree with attributes and arrays.
• JSON to XML Converter — Convert JSON to well-formed XML — supports attributes, custom root, declaration.
• CSV Viewer — Open CSV or TSV files in your browser — sort, search, paginate, export filtered view.
• JSON to CSV Converter — Convert JSON data to CSV format. Export to spreadsheets easily.
• CSV to JSON Converter — Convert CSV data to JSON format. Useful for API development.
• JSON Formatter — Format, beautify, or minify JSON with customizable indentation.
• JSON Validator — Validate JSON syntax and find errors with line and column numbers.
• HTML Minifier — Compress HTML by removing comments, whitespace, and line breaks.
• CSS Minifier — Minify CSS by stripping comments, whitespace, and unnecessary characters.
• JavaScript Minifier — Compress JavaScript by removing comments, whitespace, and empty lines.
• Base64 Encoder/Decoder — Encode text to Base64 or decode Base64 back to text. UTF-8 support.