OpenAnyFile
What is a .o file?
Object File is an executable format developed by various toolchains. It is usually created by gcc, clang, MSVC.
Compiled but not linked machine code; the linker combines .o files into an executable.
File details
| Full name | Object File |
|---|---|
| Category | Executables |
| MIME type | application/x-object |
| Signature (magic bytes) | 7F 45 4C 46 (ELF), 4C 01 (COFF) or CF FA ED FE (Mach-O) |
| Developer | various toolchains |
| Opens with | Executable inspector |
| Uploaded? | No — read locally in your browser |
How to open a .o file
OpenAnyFile routes .o files to its executable inspector, which shows the headers, sections and imported libraries — without running it.
- Drop your .o file on the box above, click it to choose the file, or paste it with Ctrl+V.
- The real format is detected from the file's first bytes — not just its name.
- The file opens in the executable inspector.
- Use fullscreen for a closer look, check its checksums, or download it back unchanged.
What works — and what does not
Works
Viewing and inspecting: the headers, sections and imported libraries — without running it. Size, type, signature and checksums are always shown.
Does not work
Editing and saving back. OpenAnyFile is a viewer, not an editor — for changes you still need the original app.
Is it safe to open a .o file online?
Here, yes — because nothing is uploaded. Most "online viewers" send your file to their server. OpenAnyFile reads it with your browser's File API and decodes it on your own device, so there is no copy anywhere else. You can check: open your browser's network tab while opening a file — no upload appears.
Questions about .o files
Can I open a .o file without installing software?
Yes. OpenAnyFile opens .o files in your browser using its executable inspector. You get the headers, sections and imported libraries — without running it, with nothing installed and no account.
How do I know a file is really a .o file?
Check its first bytes instead of its name. A genuine O file begins with 7F 45 4C 46 (ELF), 4C 01 (COFF) or CF FA ED FE (Mach-O). OpenAnyFile shows the detected type, so a renamed file is easy to spot.
Is my .o file uploaded anywhere?
No. The file is read locally by your browser and never sent to a server — it even works offline once the page has loaded.
Does it work on phones?
Yes — on Android and iPhone, in any modern browser. You can also install OpenAnyFile as an app.
Related formats
Other formats from the same family:
Format facts checked and page updated on September 25, 2026.