Content-Type Header Builder

The Content-Type Header Builder is a free browser-based tool that helps developers construct syntactically correct Content-Type HTTP header values. The Content-Type header tells the server or client what media type the body of the request or response contains. Getting it wrong can cause parsing failures, character encoding issues, or rejected API requests. This tool removes the guesswork by letting you pick from a curated list of MIME types organized by category, add the appropriate charset and boundary parameters, and copy the result in multiple output formats.

The builder supports every common media type you are likely to encounter in web development: application/json for REST APIs, application/x-www-form-urlencoded for classic form submissions, multipart/form-data for file uploads, XML and SOAP variants, plain text, HTML, and binary types like application/octet-stream or application/pdf. You can also enter a fully custom MIME type for vendor-specific or experimental media types. For multipart types the tool auto-generates a random boundary string that you can customize or regenerate with a single click.

Once you have configured your Content-Type value, choose from four output formats: a raw HTTP header line, a curl -H flag ready to paste into your terminal, a JavaScript fetch() headers snippet, or an axios configuration object. Quick presets for common scenarios like JSON API, Form POST, File Upload, GraphQL, and XML SOAP let you jump straight to the right value without any manual selection.

If you need to inspect the headers your server is returning, try the HTTP Header Analyzer. To convert a full curl command into code, check out the cURL to Code converter. For a reference of HTTP response status codes, see the HTTP Status Codes lookup.

All processing runs entirely in your browser. No data is transmitted to any server. Your header values and API details remain private.

1. Choose a Category from the dropdown (JSON, Form Data, Multipart, XML, HTML, Plain Text, Binary, or Custom).
2. Select the specific MIME Type from the filtered list, or type your own when using the Custom category.
3. Optionally set a Charset parameter (e.g. utf-8, iso-8859-1) to specify character encoding.
4. For multipart types, review the auto-generated Boundary string or click the refresh icon to generate a new one.
5. Add any Additional Parameters as key=value pairs, separated by semicolons or newlines.
6. Pick an Output Format: Header value, curl -H, fetch(), or axios.
7. Click Copy or press Ctrl+Shift+C to copy the result to your clipboard. Use the Quick Presets for common scenarios.