How to open .MJS files on Mac
To open .MJS files on Mac, to view or edit: Control-click the .mjs file → Open With → choose a code editor (or any text editor).
Step-by-step instructions
- To view or edit: Control-click the .mjs file → Open With → choose a code editor (or any text editor).
- To run with Node.js: open Terminal, cd to the file’s folder, and run: node yourfile.mjs.
Common issues
The file opens as plain text or “unknown file type”
Many systems don’t assign a default app for .mjs even though it’s just JavaScript source code.
- Open it with a code editor or any plain-text editor using “Open with”.
- If you work with .mjs frequently, set your preferred editor as the default app for this extension.
Node.js errors about modules (import/export not working)
Module behavior depends on how Node.js decides whether a file is an ES module; .mjs is one explicit signal to use the ES module loader.
- Confirm the file name ends with .mjs and run it as: node yourfile.mjs.
- If you copied code from a .js project, make sure it uses ES module syntax and that you are running it in a context that supports ESM.
Web/server MIME type problems when hosting .mjs
If a server sends the wrong JavaScript media type, browsers and tools may refuse to load it as expected.
- Configure your server to send a JavaScript media type such as text/javascript for .mjs responses.
- Verify the Content-Type header in your browser’s developer tools or network inspector.
Security note
.mjs files are executable code when run in a JavaScript runtime (for example, Node.js). Only execute .mjs files you trust, because they can read/write files or make network requests depending on what the script does.