OBJ files are commonly used for 3D models and are compatible with many 3D modeling and animation software. If you're a Mac user and need to open an OBJ file, here are a few methods to do so.

1. Use Preview: If the OBJ file contains 3D models with textures, you can actually preview it using the built-in Preview app on your Mac. Simply right-click on the OBJ file, select 'Open With,' and then choose 'Preview.' You can then navigate through the 3D model using your mouse and view it from different angles.

2. Use 3D Modeling Software: Another option is to use 3D modeling software that supports OBJ files, such as Blender or Autodesk Maya. These programs are more advanced and allow you to not only open OBJ files but also edit and manipulate the 3D models to your liking.

3. Use Online Converters: If you don't have any specific software installed, you can use online converters to convert the OBJ file into a more common format that your Mac can open. There are many free online converters available, and all you need to do is upload the OBJ file, select the desired output format, and then download the converted file to your Mac.

4. Use Quick Look: In the Finder, you can simply select the OBJ file and press the spacebar to use Quick Look, which will give you a quick preview of the 3D model without needing to open any specific software.

5. Use 3D Viewer Apps: There are also dedicated 3D viewer apps available on the Mac App Store that can open and display OBJ files with ease. These apps offer additional features and viewing options for 3D models.

By using these methods, you can easily open OBJ files on your Mac and view 3D models without any hassle. Whether you're a 3D artist, designer, or just need to view a 3D model for reference, these options will allow you to access and interact with OBJ files on your Mac.