Many a times it happens that users are unable to access or process their files properly on Mac due to emergence of no mountable file system error. Usually this type of issue is encountered when the OS fails to mount file system on Mac. file system on Mac can get corrupted due to any possible reason such as virus attack, unintentional deletion, damaged directory and many more. However there is no need to worry about because no mountable file system error can be fixed easily. In such situation you can take the help of disk utility. It is a built in facility used to resolve common corruption issues on Mac. But if unfortunately it fails to function properly and the error remains unsolved then there is no other option but to reinstall the Operating system. Reinstalling OS will fix no mountable file system error completely but before any further action it is important to know that reinstalletion of OS will wipe all the data stored on your hard drive. Therefore it will be sensible to have a proper backup of all your files before doing so. However you can also use third party Mac Data Recovery Software in order to rescue your files after resolving no mountable file system error on Mac.