JavaScript is the programming language of the web — the only language that runs natively in every browser, powering interactive websites and full applications.
Use caution
Type Code
By Brendan Eich / Ecma International
MIMEapplication/javascript
Drop any file to identify it
No upload. No signup. No sending your file halfway across the internet. We tell you what it is, right here in your browser.
You're looking at a .js file. It could be a tiny script that validates a form, or it could be the engine behind an application as complex as Google Docs or Figma. JavaScript is the only programming language that runs in every browser on earth, which means it's the only choice for anything interactive on the web.
Brendan Eich built the first version in ten days in 1995, and the internet has been living with that decision ever since. Then Node.js took it server-side, and suddenly the same language that handled button clicks was also running databases, APIs, and build tools. JavaScript is messy, inconsistent, and full of historical quirks that developers love to mock (ask someone what `0 == []` evaluates to). It is also, by any measure, the most widely deployed programming language in human history.
Any text editor opens .js files. VS Code is the standard development environment. Your browser runs JavaScript natively — open the developer console and you can type it live. Node.js runs it outside the browser. TypeScript (which compiles to JavaScript) adds type safety for larger projects. Love it or hate it, JavaScript is the gravity of the web — everything falls toward it eventually.
Technical details
Full Name
JavaScript
MIME Type
application/javascript
Developer
Brendan Eich / Ecma International
Magic Bytes
N/A
Safety
.js requires caution. JavaScript files can execute code. Only run JS files from trusted sources.
What opens it
Any text editor
FREEAll
VS Code
FREEAll
Any web browser (via HTML)
FREEAll
FAQ
What is the difference between JavaScript and TypeScript?
TypeScript is JavaScript with added static types — you declare what kind of data each variable holds, and the compiler catches mistakes before runtime. TypeScript compiles to plain JavaScript, so it runs everywhere JS does. Most large projects now use TypeScript for its safety benefits, but JavaScript remains the runtime language.
Is a .js file safe to open?
Opening a .js file in a text editor is perfectly safe — you’re just reading code. Running it is a different matter. A .js file executed by Node.js or loaded into a web page can do anything its environment permits. Only run JavaScript files from sources you trust.
What is the difference between JavaScript and Python?
JavaScript runs natively in browsers and dominates web development. Python dominates data science, AI, and automation. JavaScript is event-driven and asynchronous by nature; Python prioritises readability and simplicity. Many developers learn both — JavaScript for the web, Python for everything else.