Defragmenting

When you (or the operating system) defragment the file system in which a file-hosted VeraCrypt container is stored, a copy of the VeraCrypt container (or of its fragment) may remain in the free space on the host volume (in the defragmented file system). + This may have various security implications. For example, if you change the volume password/keyfile(s) afterwards, and an adversary finds the old copy or fragment (the old header) of the VeraCrypt volume, he might use it to mount the volume using an old compromised + password (and/or using compromised keyfiles that were necessary to mount the volume before the volume header was re-encrypted). To prevent this and other possible security issues (such as those mentioned in the section +Volume Clones), do one of the following:

Use a partition/device-hosted VeraCrypt volume instead of file-hosted.
Securely erase free space on the host volume (in the defragmented file system) after defragmenting. On Windows, this can be done using the Microsoft free utility +SDelete (https://technet.microsoft.com/en-us/sysinternals/bb897443.aspx). On Linux, the +shred utility from GNU coreutils package can be used for this purpose. +
Do not defragment file systems in which you store VeraCrypt volumes.