What Is a .h File? .h Format, MIME & How to Open

Quick facts

Extension.h

File typeC Header File

MIME typetext/x-c

CategoryData & Text

Charset—

Compressible—

Format familyc

What is .h

What is a .h file?

A .h file is a C Header File — C/C++ header file with declarations.

In the mime-db registry it maps to text/x-c. When serving .h over HTTP, set the Content-Type header as shown in Developer info below.

Related entities: it maps to text/x-c and is used by C, C++ among others — and is delivered over HTTP via the Content-Type header.

How to open .h files

Use VS Code or GCC to open and edit .h files.
Any text editor (Notepad, VS Code) can inspect the raw content as text.

Developer info

When served over HTTP, responses should set the following header:

Content-Type: text/x-c

Common software that reads/writes .h:

VS CodeGCC

Relation chain

.hextension of

format

cserved as

mime type

text/x-csent via header

http header

Related extensions

Related MIME types

Related programming languages

Common uses

Configuration files
Data interchange between systems
API request and response payloads
Logs and data exports

How to edit .h files

Open the file with VS Code, make your changes and save.
Most editors preserve the original formatting and encoding — avoid changing the charset.

How to create .h files

Create a new file and save it with the .h extension, or export this format from VS Code.

Frequently asked questions

What programs can open .h files?

Common options include VS Code, GCC. You can also open many of these files with built-in viewers or a browser.

How do I create a .h file?

Create a new file in any text editor or the app that owns the format and save it with the .h extension.

What is the relationship between .h and the text/x-c MIME type?

text/x-c is the media type identifier used for .h files during network transfer (for example in the HTTP Content-Type header).

Sources & standards

Updated 2026-08-18

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