Web Developer Tools

These utilities close the gap between your browser and the APIs you work with — inspect headers, convert curl commands to JavaScript Fetch, test endpoints, and decode user agent strings.

• User Agent ParserParse any User-Agent string into browser, OS, and device.
• Curl to FetchConvert curl commands to JavaScript fetch() code.
• HTTP Header CheckerInspect HTTP response headers for any URL.
• REST API TesterSend GET, POST, PUT, PATCH, DELETE requests with headers, query params, and JSON body. View pretty-printed responses with status codes.
• CSP Header GeneratorBuild Content Security Policy headers interactively — toggle directives, configure source lists, and get the header value, Nginx config, Apache config, and HTML meta tag output.
• IP Subnet / CIDR CalculatorCalculate network address, broadcast, subnet mask, wildcard mask, host range, and usable host count from any CIDR notation. Identifies private ranges and IP class.
• MIME Type FinderLook up MIME types by file extension or search by content type. Covers images, video, audio, fonts, Office formats, and developer file types — 55+ MIME types with copy support.
• Fetch → cURL ConverterConvert JavaScript fetch() code to an equivalent cURL command — parses URL, method, headers, and JSON body automatically. Paste the fetch() call and get a terminal-ready cURL command.