Open .MJS files online

Q: How do I open a .mjs file online?

Drag the `.mjs` onto the page (or click to browse, or paste a URL). It opens in the code editor so you can read the source and its imports/exports, search, and copy — it is not executed. The file is parsed entirely in your browser and never uploaded.

Q: Is a .mjs file a text file?

Yes. It is plain-text JavaScript (UTF-8), so a `.mjs` opens in any text or code editor. The extension signals the module format, but the file is readable text.

An .mjs file is a JavaScript source file that explicitly uses ES module syntax (import/export). The .mjs extension tells runtimes like Node.js to treat the file as an ES module regardless of the project's settings, removing ambiguity between the older CommonJS style and modern modules.

ES modules are the standard JavaScript module system, supported natively in browsers and in Node. Using .mjs (or setting "type": "module") is how libraries and tools ship modern, tree-shakable code. Opening one to inspect its exports is routine when integrating a dependency.

What is a `.mjs` file?

An ES module uses static import and export statements at the top level, which lets bundlers analyze dependencies ahead of time (enabling tree-shaking — dropping unused code). This differs from CommonJS (require/module.exports), which is dynamic.

A .mjs file is plain text (UTF-8), MIME type text/javascript. The extension is a signal to the runtime; the content is ordinary JavaScript.

Node.js ES module entry points and libraries
Browser-native modules and import maps
Modern build tooling and bundler configuration
Tree-shakable library distribution

How to open a `.mjs` online

Open the zip viewer in a new tab, then drop your .mjs onto the page — or click to browse for it, or paste a URL. The file opens in the Monaco code editor, with syntax highlighting, code folding, and find, read entirely on your device.

Drag your .mjs onto the page — or click to browse, or paste a URL.
It opens immediately in the Monaco code editor, with syntax highlighting, code folding, and find. No install, no sign-up.
Read, search, or copy it. Your file never leaves your browser.

Open `.mjs` without uploading

Most "open mjs online" sites work by uploading your file to a server and processing it there. ZipTool does the opposite: it loads its parser once, then reads your .mjs locally in the browser tab. The contents stay on your device.

You can prove that in seconds. Open the page, press F12 for DevTools, switch to the Network tab, and open your file — no request carrying the file's contents is sent. You can also turn off Wi-Fi after the page loads and the file still opens. See security and privacy for the full picture.

Frequently asked questions

How do I open a .mjs file online?

Drag the .mjs onto the page (or click to browse, or paste a URL). It opens in the code editor so you can read the source and its imports/exports, search, and copy — it is not executed. The file is parsed entirely in your browser and never uploaded.

Can I view a .mjs without uploading it?

Yes. ZipTool reads the file locally in your browser tab — no upload, no server-side copy. Confirm it with DevTools (F12, Network tab) while opening the file, or by turning off Wi-Fi after the page loads and verifying the file still opens.

What is the difference between .js and .mjs?

The content is both JavaScript; the difference is the module system the runtime assumes. .mjs always means an ES module (import/export). A .js file is CommonJS or ESM depending on the nearest package.json. Using .mjs removes that ambiguity.

Is a .mjs file a text file?

Yes. It is plain-text JavaScript (UTF-8), so a .mjs opens in any text or code editor. The extension signals the module format, but the file is readable text.