Everything about how ChatLAN works, its security model and what to check when something doesn't connect.
How can it work without the internet?
ChatLAN talks directly between computers over your local network (LAN or Wi-Fi router). The internet connection is simply never used — if your office network is up, ChatLAN is up.
You still need any local network — a home/office router, a switch, or even a phone's Wi-Fi hotspot with no upstream internet works fine. ChatLAN only ever talks over that local segment.
Two PCs can't see each other. What do I check?
Open ☰ → Network diagnostics in the app — it checks your IP, firewall rule and gateway automatically. The most common causes: the PCs are on different subnets/VLANs, or the Wi-Fi router has "AP/Client Isolation" enabled (turn it off in router settings). You can also connect manually by IP from the ☰ menu.
The diagnostics screen also shows each device's discovered peers in real time, which helps confirm whether the problem is network-wide or specific to one machine. If two PCs are on different Wi-Fi bands or VLANs set up by your router, ask your network admin to bridge them, or connect manually by IP as a workaround.
Does any of my data leave the network?
No. There are no ChatLAN servers. Messages, files and history exist only on the machines in your network, encrypted in transit with TLS.
Even file transfers go directly between the sending and receiving PC over the TLS-encrypted file channel — nothing is ever relayed through a third party, cloud storage, or a ChatLAN-operated server, because none exists.
Windows SmartScreen warns me about the installer.
The current build isn't code-signed yet (signing certificates are on the roadmap). Click "More info" → "Run anyway". The installer only adds the app and a firewall rule; you can verify the rule under Windows Firewall → "ChatLAN".
Code signing is planned once the project reaches a stable release; it removes the SmartScreen prompt but does not change what the installer actually does. You can always inspect the firewall rule it creates under Windows Firewall → "ChatLAN" to confirm it only opens the ports the app needs.
Is it really free?
Yes — chat, groups, LAN file transfer and every work tool are 100% free, with no machine limit and no subscription. A plugin marketplace is planned for later, handled entirely inside the app for teams who want optional add-ons — the core messenger stays free.
There's no trial period, no machine limit and no feature paywall — every chat, file transfer and work tool is free. Down the road, ChatLAN will add an in-app plugin marketplace for optional add-ons, purchased and managed entirely inside the app; it won't touch the free core messenger.