Many cracks are used as Trojan horses to install keyloggers, backdoors, or ransomware that can steal your passwords and banking information.
Instead of risking your digital security with a crack, use these trusted, free tools that are widely considered industry standards. How to Convert MKV to MP4
Searching for a "free download mkv to mp4 converter with crack" might seem like a way to save money, but using "cracked" software—which has its security modified by unknown third parties—is highly dangerous and unnecessary.