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 .mjs file
You have a MJS file and nothing on your machine will touch it. Here is what the format actually is, and how to read one in about four seconds without installing anything.
What is a .mjs file?
ES Module JavaScript is a code format developed by TC39 / Node.js, first appearing in 2017. It is normally produced by Node.js projects.
Tells Node to parse the file as an ES module (import/export) rather than CommonJS, regardless of the package.json type field.
| Full name | ES Module JavaScript |
|---|---|
| File category | Code |
| MIME type | text/javascript |
| Developer | TC39 / Node.js |
| Introduced | 2017 |
| Usually created by | Node.js projects |
| OpenAnyFile engine | syntax highlighter |
| Opens without upload | Yes — parsed locally in your browser |
Open a .mjs file in your browser
OpenAnyFile routes .mjs 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 .mjs 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 MJS 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. Works the same on Windows, macOS, Linux, Android and iOS, because it is just a web page.
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.
Is it safe to open a {E} file on a website?
It depends entirely on whether the website uploads it, and almost all of them do. That is a real problem when the code file in question is a contract, a client deliverable or something under NDA. OpenAnyFile removes the question: the decoding happens inside your browser tab, so there is no transfer, no queue, no temporary storage and no retention window to read about in a privacy policy.
Frequently asked questions about MJS files
Can I open a .mjs file without installing special software?
Yes. OpenAnyFile's syntax highlighter runs in your browser, so you can read a MJS 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 .mjs file actually contains?
The .mjs 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 MJS 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 .mjs file, exactly?
ES Module JavaScript — a text/javascript format created by TC39 / Node.js since 2017. Tells Node to parse the file as an ES module (import/export) rather than CommonJS, regardless of the package.json type field.
Does the same viewer handle formats related to MJS?
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 .mjs file, it will open too: