There are two downloads available for Windows users.
Windows 64-bit with JDK 8 Included: This archive includes both SQL Developer and an embedded copy of the Java 8 Development Kit (JDK). Simply extract the zip to a fresh directory and run the sqldeveloper.exe in the top directory. The EXE is configured to run the embedded JDK by default.
Note: the Windows EXE requires a MSVCR100.dll to run. Most computers will already have this file and in the Windows PATH. However, if the first copy of the file found by the EXE is a 32-bit copy of the DLL, then SQL Developer will fail to start. You can fix this by copying a 64-bit version of the DLL into the BIN directory or updating your OS PATH such that a 64 bit copy of the DLL is found first.
Windows 32-bit/64-bit: This archive. will work on a 32 or 64 bit Windows OS. The bit level of the JDK you install will determine if it runs as a 32 or 64 bit application. This download does not include the required Oracle Java JDK. You will need to install it if it's not already on your machine.
If SQL Developer cannot find Java on your machine, it will prompt you for the path for a JDK home. This only occurs the first time you launch SQL Developer. A valid Java Home on Windows will be similar to C:\Program Files\Java\jdk1.8.0_181