Can You Run a JAR File Online? (What a Browser Can and Cannot Do)

No browser executes a JAR directly — applets and Web Start are gone. What online Java tools actually run, what you can do with a JAR in the browser, and when you still need java -jar.

What You Actually Want

What You Can Do With a JAR in the Browser

Online Java Playgrounds Are a Different Thing

The One Real Browser JVM

Old Phone Games (.jar and .jad)

When You Do Need to Run It Locally

Summary