Naming runtime solutions (FileMaker Pro Advanced)
The filename extension associates all of the runtime solution files with the runtime application. If a user has more than one runtime database solution on a machine, the filename extension together with the binding key will ensure that the correct runtime application is started when a solution file is double-clicked. Use an extension that is unique to your users’ computer systems.
Consider the following points when naming runtime solutions:
The Developer Utilities automatically update all files to use the extension that you specify and append the extension to the filenames. FileMaker data source references used in relationships, scripts, and external value lists are updated to interact with the new filenames.
Assigning the extension for Windows solutions
The extension registers your runtime application with the Windows operating system. The extension is used by Windows to determine which application starts when you double-click a solution file. The Developer Utilities append the extension to all database filenames in the runtime database solution during the binding process.
Assigning the extension for OS X solutions
In OS X, the first three characters of the extension are used in the creator code for the runtime application. The creator code is still used by some older technologies in OS X and should be unique to ensure that OS X can determine the difference between different runtime applications. The creator code is only stored in the runtime application.
Because creator codes are four characters, the Developer Utilities constructs the code by using the first three characters of the extension and inserting an uppercase "F" after the first character. For example, the default five-character extension "fmpur" becomes the "fFmp" creator code. Creator codes are case-sensitive.
Note  Creator codes should be registered with Apple Inc. to verify that the creator code you choose is unique. You may use the .fmpur five-character extension because FileMaker has registered the fFmp creator code with Apple Inc. Contact Apple Developer Support or visit their website at to register any other creator codes.
Conflicts with non-unique filename extensions in Windows
If the extension is not unique, it might cause registry conflicts in Windows. For example, if you use the .fmp12 extension for your runtime database solution and your users have FileMaker Pro installed on their hard disks, all of their FileMaker Pro document icons will change to the runtime icons. Additionally, FileMaker Pro documents will no longer automatically open the FileMaker Pro application.
To restore the document icons to the original FileMaker Pro document icon:
Related topics 
About creating runtime solutions (FileMaker Pro Advanced)
Preparing files for a runtime solution (FileMaker Pro Advanced)
Binding files into a runtime solution (FileMaker Pro Advanced)
Distributing runtime solutions (FileMaker Pro Advanced)
Importing data into upgraded runtime solutions (FileMaker Pro Advanced)
Starting runtime solutions (FileMaker Pro Advanced)
Recovering runtime files (FileMaker Pro Advanced)