Are you dealing with Mac OS blue screen startup? It is a common issue mainly occurs due to damage startup items. In such situation you neither can access your data and nor can resolve the problem unless or until you boot up in your Mac system. Although you can boot your machine in single user mode and can get access to your data in command mode, but would only be a temporary solution of Mac OS blue screen startup. It will also require good technical skills in order to operate your system in command mode. However formatting is rather an easy and convenient way to troubleshoot this problem. It is surely a bit risky to format the entire Mac system, it will remove all the data stored on your hard drive but meanwhile it is the only way to resolver Mac OS blue screen startup issue as well. As far as the matter of your formatted data is concern, you can easily get back all your files with using third party Mac Data Recovery Software. It is very effective, safe and easy to use tool to recover or restore any lost formatted, inaccessible or deleted data on Mac. Thus fix the Mac OS blue screen startup as soon as possible.