The new version of FileMaker offers a lot of great new features. Card style windows, copying value lists, new functions, a REST API and much more.
But you need to verify whether your solutions works fine with the new release before you upgrade. This includes checking whether all layouts still work the same. Scrollbars went away, so windows are a bit smaller or show a bit more content. The zoom controls are gone, so you may need to make your own if users miss them. Some things layout differently now in FileMaker Go 16 compared to 15.
On Windows having no parent window around your layout windows causes changes. Some scripts don’t work anymore and need to be updated for that situation. For your users you should always have a menubar in one of the visible windows available. Because if you hide all menu bars, there is no way to use the menus.
Next some things under the hood changed. WebViewer now uses a newer WebKit version on Mac with a different API. When I first got a preview of FileMaker 16, all my plugin functions for web viewer failed. Over time I got most working again, but still there are major things missing. For example WKWebView does hardly any printing. A couple of Cocoa developers run into this and I did not get it to print for my plugins. Better not move to FM 16 if you need WebView printing or PDF generation.
For using fmp URL there is a new permission setting in security dialogs. You need to enable it for your solution to continue to use this feature as before.
The new version include external script steps defined in plugins. While this is a nice addition, I will currently not use them until we no longer need to use FileMaker 15 and older. The script steps show as missing steps in older versions and only a DDR may show the ID of the missing plugin.
If you are FBA or VLA, please check the changes in the agreements. FBA members in the US must now have a General Liability Insurance.
Nevertheless FileMaker 16 is a big step forward for FileMaker and offers a ton of new features, fixes hundreds of old bugs and certainly helps to grow the community!
See also: FileMaker 16.0.1 data integrity disclaimer
Update: Erweiterte Version der Geschichte auf Deutsch in FileMaker Blog.