During the installation of FlashDevelop, it's possible to choose not to download and install Adobe Flex SDK. This option is useful in case Adobe Flash Builder is already installed or Adobe Flex SDK is already downloaded manually before. Unnecessary download and waste of disk space caused by redundant files are avoided by sharing Adobe Flex SDK between Adobe Flash Builder and FlashDevelop.

Configuring FlashDevelop to use Adobe Flex SDK included in Adobe Flash Builder:

1. Run FlashDevelop

2. Go to Tools->Program Settings

3. Select AS3Context on the left side, second item under Plugins.

4. Look for Flex SDK Location under Language.

5. Enter C:\Program Files\Adobe\Adobe Flash Builder 4\sdks\4.1.0

6. Select FlashViewer on the left side.

7. Look for External Player Path under Misc.

8. Enter C:\Program Files\Adobe\Adobe Flash Builder 4\sdks\4.1.0\runtimes\player\10.1\win\FlashPlayerDebugger.exe

9. Close Settings window.

The paths may vary depending the location of the Adobe Flex SDK or Adobe Flash Builder version.