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What is the difference between Java and JavaScript?
Updated 2 min read7 differences
In short
Java is a statically typed language compiled to bytecode for the JVM; JavaScript is a dynamically typed language that runs in browsers and on Node.js.
Java
Java is a statically typed, object-oriented programming language that compiles to bytecode for the Java Virtual Machine, so programs run on many platforms.
Read the page on JavaJavaScript
JavaScript is the programming language that runs in web browsers to make pages interactive, and it also runs on servers through runtimes like Node.js.
Read the page on JavaScriptJava and JavaScript compared
| Aspect | Java | JavaScript |
|---|---|---|
| Typing | Static, checked by the compiler | Dynamic, checked while the program runs |
| Runs on | The JVM, on servers, desktops and Android | Browsers, plus Node.js, Deno and Bun on servers |
| Execution | Compiled to bytecode, then JIT-compiled by the JVM | Run from source by a JIT-compiling engine such as V8 |
| Code structure | Classes and interfaces | Functions, objects and prototypes; classes are optional syntax |
| Concurrency | Many threads, including lightweight virtual threads | One main thread with an event loop; workers for parallel work |
| Typical use | Enterprise backends, big data, Android apps | Web front ends, Node.js backends, full-stack apps |
| Standardized by | The Java Community Process, with OpenJDK as reference | Ecma International, as ECMAScript |
The difference, explained
Despite the names, Java and JavaScript are separate languages with different designs. Java, released by Sun Microsystems in 1995, is a statically typed, class-based language compiled to bytecode for the Java Virtual Machine. JavaScript, created at Netscape the same year in about ten days, is a dynamically typed language that runs in every web browser and on servers through runtimes such as Node.js.
The name was a marketing decision: Java was the most talked-about language of the moment, and Netscape renamed its scripting language, first called Mocha and then LiveScript, to ride that wave. Some syntax looks alike, with curly braces, if and for, but the similarity stops there. Developers like to say the two are as related as car and carpet.
They work very differently. In Java, every variable has a type the compiler checks, code lives in classes, and the JVM compiles frequently run code to fast machine code. In JavaScript, types are checked only while the program runs, functions are values you can pass around, objects inherit from prototypes, and a single thread handles slow work asynchronously with promises and async/await.
They often meet in the same system: a JavaScript front end in the browser talking over HTTP to a Java backend built with Spring Boot. Browsers once ran Java through applets, but those were retired years ago, so the front end belongs to JavaScript and languages that compile to it, such as TypeScript. A common misconception is that JavaScript is a lighter version of Java; it is a full language of its own, standardized as ECMAScript.
Which one should you use?
Choose Java when…
- You build large backend systems that benefit from compile-time checks.
- You work in a JVM ecosystem with Spring or big-data tools.
- You need many threads doing CPU-heavy work in one process.
Choose JavaScript when…
- You build anything that runs in a web browser.
- You want one language for both the front end and the back end.
- You want quick iteration and the huge catalog of npm packages.
Readers ask
Is JavaScript related to Java?
No. The similar name came from a 1990s marketing decision, and the languages differ in typing, runtime and design. They share only some C-style syntax.
Should I learn Java or JavaScript first?
JavaScript, if you want to build websites, since it runs in every browser with no setup. Java, if you aim for backend, enterprise or Android work and want a stricter language that teaches types early.
Can Java run in a web browser?
Not directly anymore. Browser applets were retired years ago, so browsers run JavaScript and WebAssembly; Java code reaches the browser only through tools that compile it to one of those.