Frequently Asked Questions
The most common questions about CERNIS PRO — answered briefly and honestly.
What does CERNIS PRO actually do?
It shows you which devices are on your home network, who they talk to and whether anything looks unusual — and explains every finding clearly. An honest, understandable overview of your own network.
Does CERNIS PRO send my data anywhere?
No. There is no CERNIS server, no account, no telemetry. All data stays local on your machine. A few functions (such as loading an operator name or the external IP check) only talk to an external helper service at your explicit request — clearly recognisable and optional in each case.
Do I need an account or a subscription?
No. Download, install, use. No login, no subscription.
Is CERNIS PRO free / open source?
CERNIS PRO 2.0 is open source under the GPL. The source code can be viewed and verified.
Do I have to be a network expert?
No. The interface is made for interested non-experts, and every function comes with help in plain language. At the same time there is enough depth that professionals get their money’s worth too.
Does CERNIS block or change my network traffic?
No. CERNIS observes and explains — it does not interfere with your traffic. It is an observer, not a firewall.
Why does CERNIS want elevated permissions?
Some deep functions (e.g. passively reading the requested host names) need elevated system permissions. CERNIS says so openly and never takes permissions in secret. Technically, only a tiny, specialised helper carries the required permission — not the whole application.
Does CERNIS see encrypted connections too?
For encrypted connections it sees the target host name (via SNI) and attributes it to the program responsible — not the content. So you know where an app is talking without the encryption being touched. This data is not stored permanently.
Does it work with my FRITZ!Box?
Yes — CERNIS offers a rich FRITZ!Box detail view via the official TR-064 interface (connection data, DSL, WLAN clients, event log, port forwardings).
Can I create reports?
Yes, six report types as PDF, plus CSV/JSON export — for archiving or sharing.
What happens to my data if I uninstall CERNIS?
It is gone. Everything was local; there is no copy “somewhere”.
Which languages are available?
German and English, switchable at any time — including the built-in manual.