File Extension CLASS

  • Full name
    Java Bytecode Class Format
  • Developer
  • Popularity
Have you encountered a problem with a CLASS file? Don’t you know which program opens a file with this extension? You will find all the information you need about working with a CLASS file here. In the further part of this page we have added a list of programs that should open your CLASS file. It is enough you choose a proper application for your operating system, download and install it.


With the file extension class, CLASS files of the Java programming language are identified. (Classes Are Programming Constructs) Source code files (file extension java) are compiled into so-called (virtual) machine-readable CLASS files and contain bytecode. This bytecode is only executable in a Java virtual machine (JVM). Since there are JVMs for many different systems, Java is considered a platform-independent programming language.

Each CLASS present in a source code is compiled into a separate CLASS file, which is usually summarized in a jar file. If a JVM is installed, java files can be compiled with the javac command. Alternatively one can also use a Java IDE (integrated development environment), for example Eclipse for Java.

Since there are different versions of the JVMs (1.4, 1.5 and 1.6), it may happen that a CLASS file on certain JVMs may not work. Note that JVMs CLASS can only execute files but not generate them.

The developer of Java - Sun Microsystems - has since been bought by Oracle. A common name for the JVMs is the Java Runtime Environment (JRE).

Programs which can open a CLASS file

How to open a CLASS file? Advice and guidance

Absolutely most often appearing reason that prevents you from opening the CLASS file is the lack of a proper application to support it in your operating system. It is notably the first thing you need to address. When one of the programs to support a CLASS file from the list is already installed, you can try to rerun the file. The system should display a message asking you to choose a primary application to support CLASS files. At this point we are looking for disk space where the application was installed in and we can link it with a CLASS file. Since then, our operating system will use the selected program to support all CLASS files.

Other issues

Despite the described problem with CLASS there may be many more problems. If the existing operations were not effective, get involved with the following matters:

- verify that the CLASS file is not damaged and that it has been downloaded or copied in whole
- verify that the file has a file extension that has not been intentionally changed (for example, if it do not contain other information than its extension suggests)
- make sure again whether the CLASS file type is linked in the operating system with a proper program
- make sure that the file is not infected with a virus and you have up to date software and drivers.

Similar extensions