Cryptomator in a LAN:

Let assume a Cryptomator vault is created on a shared folder/drive in a LAN. Does it allow multiple users access it at the same time?

I can’t answer definitively but it seems this should be fine. In the case of Windows, you’re already accessing the vault as a shared network mount. The Cryptomator software on each machine is presumably using the Windows filesystem API to access the encrypted vault documents, deencrypt them, and present them to you as residing on a network drive. Apart from conflicts created by native locking requested by various applications such as Word (and the OS itself), there shouldn’t be any reason why two different users can’t access the same vault.

You can use Cryptomator with the same vault unlocked on multiple PCs simultaneously. Doesn’t matter if the backing storage is on a LAN or WAN.

When two people edit the same file in the same vault at the same time, there will be synchronization conflicts of course.

Or do you mean a different scenario: Have multiple PCs in a LAN connect to the WebDAV share of one single Cryptomator process running on one machine?

In this case the answer is no. The WebDAV share is only visible to localhost and can not be accessed via the network. If you have the requirement, you can use Cryptomator CLI and use the --bind parameter to allow access from other hosts.

Keep in mind that there is no transport encryption, though. Do not use it if you’re not certain your network is 100% trustworthy. If you don’t want to think about these kind of problems, you might be interested in Defendor, our new project for small and medium sized companies.