What is a .mtl file?
A .mtl file is an OBJ 3D model material library. Its registered MIME type is model/mtl, which places it in the 3D model family of formats.
Technically it is a specialised form of text/plain (the .asc format), so tools that understand that format can often read at least part of it.
MTL is a text-based format: the contents are readable characters, so any text editor can open it, and it compresses well.
MTL file format details
| Extension | .mtl |
|---|---|
| Format | OBJ 3D model material library |
| MIME type | model/mtl |
| Category | 3D model |
| Text or binary | Text |
| Based on | text/plain |
| File signature | None fixed |
| Registered with IANA | Yes |
| Other extensions | None |
How to open MTL files
| Windows | MTL files are plain text, so Notepad opens them: right-click the file, choose Open with, then Notepad. Notepad++ and VS Code are free and show long files more comfortably. |
|---|---|
| Mac | TextEdit opens plain text files. For code or data files, a free editor such as BBEdit or VS Code keeps the formatting intact. |
| iPhone and iPad | Save the file to the Files app and tap it; iOS previews most plain text. Or drop it on the viewer above, which shows the text right in the browser. |
| Android | Most file manager apps open plain text files in a built-in viewer. The viewer above also works in Chrome. |
Can you convert a .mtl file?
TapToConvert does not convert MTL files. The usual route is to open the file in the program that made it and use its Export or Save as option.
MTL file FAQ
What is a .mtl file?
A .mtl file is an OBJ 3D model material library, with the MIME type model/mtl.
How do I open a .mtl file?
With any text editor, such as Notepad on Windows or TextEdit on a Mac, or with the viewer on this page.
Is a .mtl file safe to open?
MTL files hold data rather than programs, but any file from an unknown source can be crafted to exploit the software that opens it. Keep that software up to date. The viewer on this page only reads the bytes and never runs anything.
What is the MIME type of .mtl?
model/mtl. Web servers send this type so browsers know how to handle the file.
Is MTL a text or binary format?
Text. Its contents are readable characters.
File type facts come from the IANA media type registry, the mime-db project and the freedesktop.org shared MIME database.