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JRE

To just run Java programs on a computer, install JRE. It installs the java command that launches a JVM instance and the full Java Class Library, and it is used to start applications written in Java or other languages.

JDK installs JRE as part of its installation when using the default installation settings. JRE must only be downloaded separately and installed on computers that will not need development tools.

Mac computers running on older versions of OS X (before Apple rebranded it to macOS) used to come with a Java runtime version preinstalled, but this is not the case anymore since Oracle has taken over the development of macOS's Java SE implementation from Apple.

Two versions of the Java SE 8 JRE are available from the Oracle website:

JRE
Server JRE

JRE is supposed to be installed on 32-bit or 64-bit end user desktop machines (note that the 32-bit version is not available for all platforms), while Server JRE is meant to be installed on servers only by advanced system administrators. Server JRE is available to 64-bit systems only and does not include an installer or browser plugins, but it adds the JVM monitoring tools that we discussed earlier.