Some features in your woorkbook that we can´t be show in the browser

Hi

I can understand that not all features can be shown in browser, but is there any whay to find wich features in the file that can´t be shown? 

Is there any program or feature in Excel that can help you find what we have to change to make it work? 

I have a lot of old files that we want to save to SharePoint, We save them as the newest format but we got the issue with some features that don´t be supported in Excel Online