OpenAnyFile
Works
Viewing, inspecting and verifying. You get the source with language-aware colouring and line numbers. File details, exact byte size and the detected signature are always shown.
How to open a .h file
H files come from C and C++ projects, and the usual advice — buy the software that made it — is rarely what you need just to look inside one. This page covers what the format is and how to open it in a browser tab.
What is a .h file?
C/C++ Header is a code format developed by Dennis Ritchie, first appearing in 1972. It is normally produced by C and C++ projects.
Declarations pasted in verbatim by the preprocessor, which is why include guards exist — without them the same declarations arrive twice.
| Full name | C/C++ Header |
|---|---|
| File category | Code |
| MIME type | text/x-c |
| Developer | Dennis Ritchie |
| Introduced | 1972 |
| Usually created by | C and C++ projects |
| OpenAnyFile engine | syntax highlighter |
| Opens without upload | Yes — parsed locally in your browser |
Open a .h file in your browser
OpenAnyFile routes .h to its syntax highlighter, which highlights the source with language-aware colouring and line numbers.
- Open the OpenAnyFile opener in this browser — nothing to download or sign up for.
- Drag your .h file onto the drop zone, click to browse for it, or paste it with Ctrl+V.
- The extension is detected and the file is handed to the syntax highlighter.
- Your H opens on its own viewer page: the source with language-aware colouring and line numbers.
- Use fullscreen for a closer look, or download the file back out unchanged. Free, and free in the sense that there is no paid tier waiting behind step three.
What you can and cannot do with it here
Does not work
Editing and re-saving. OpenAnyFile is a reader, not an editor — for changes you still need special software or an equivalent.
Your {ext} file stays on your device
The entire pipeline — detection, decoding, rendering — runs client-side. Your browser hands the bytes to a decoder compiled to WebAssembly, the result is drawn to the page, and that is the whole journey. No account is created, no file is stored, and no analytics event carries your filename. This is also why there is no size limit imposed by a server: the only ceiling is your own available memory.
Frequently asked questions about H files
Can I open a .h file without installing special software?
Yes. OpenAnyFile's syntax highlighter runs in your browser, so you can read a H file with nothing installed. You get the source with language-aware colouring and line numbers. For full editing you still need the original application — this is a viewer, not an editor.
How can I tell what a .h file actually contains?
The .h extension carries no fixed signature, so the extension alone proves nothing. Opening it in OpenAnyFile shows the raw header bytes and detected type, which is the only reliable way to identify one.
Is it safe to open a H file online?
With OpenAnyFile, yes, because nothing is uploaded. The file is read locally through your browser's File API and never leaves your device, so there is no server copy to leak, log or retain. That matters most for the kind of file people are least willing to hand to a random converter site.
What is a .h file, exactly?
C/C++ Header — a text/x-c format created by Dennis Ritchie since 1972. Declarations pasted in verbatim by the preprocessor, which is why include guards exist — without them the same declarations arrive twice.
Does the same viewer handle formats related to H?
Yes — the same engine also opens .html, .xml, .sql, so you can compare related files without switching tools.
Related formats
These open with the same engine, so if you have one of these sitting next to your .h file, it will open too: