Several years ago, WhatsApp gave Android users the option of choosing to either backup their chat histories to their devices locally or to Google Drive. However it seems that backing up to Google Drive is now mandatory as WhatsApp has confirmed that chat histories that have yet to be backed up to Google Drive will be deleted.
We’re not sure when the deletion of chat histories will take place, but if you have not backed up to Google Drive yet perhaps now might be a good time to do so. Note that this only affects users on Android because WhatsApp for iOS backs up to iCloud instead. However this isn’t necessarily a bad thing as cloud storage means that you can easily restore your chat histories when you get a new handset, and can also help you sync across devices.
WhatsApp had also previously confirmed that they reached an agreement with Google where your WhatsApp backups will not count towards your Google Drive storage, although backups that have not been updated for more than a year will eventually be removed from Google Drive. There is no mention of a quota so it is unclear if this is truly unlimited or if there could be a hidden cap.
However we should point out that it was previously reported that your backup to Google Drive is not encrypted, so that should be taken into consideration if encryption is of the utmost importance to you.