If configured in the workspace settings, this API server is accessed from within LibrePCB to provide various online services.
The following services are currently provided:
When opening the library manager, the list of available libraries is fetched from this server and displayed in the library manager.
The "Order PCB" dialog in the schematic- and board editors allows to upload a LibrePCB project to this server. Afterwards the order process can be continued in a web browser. When continuing the order process, the project will be forwarded to the chosen PCB manufacturer. For details, see fab.librepcb.org/about.
In the "Add Component" dialog of the schematic editor and in the BOM export dialog, live part information (e.g. lifecycle status, availability, price, ...) may be fetched from this API for parts which provide an MPN an manufacturer name, to be displayed in the user interface. Although the underlying data is provided by a third-party (currently Partstack), this API server fully anonymizes the requests so that absolutely no data (except the requested MPN + manufacturer) are forwarded to the third-party. So not even your IP address will leave the API server.
Note that this feature can be disabled in the workspace settings dialog, then no automatic requests will be made for this purpose.
This feature was added in LibrePCB 1.1.0.
At LibrePCB we believe online services must be implemented in a privacy respecting way. Thus the API is designed with privacy in mind and no personal data is forwarded to any third-party unless you explicitly request to do so (e.g. for ordering a PCB, of course your project needs to be forwarded to the manufacturer).
Note that some API requests may be stored on our server to allow investigation of problems and to get basic statistics about the usage of our services. However, no personal data (e.g. IP addresses) will be stored for this purpose.
IP addresses of requests will be temporarily stored in server log files for security reasons, e.g. to block attacks or other suspicious activity of particular IP addresses. But these log files usually don't leave the server, only in case of suspicious activity they may be reviewed by the LibrePCB server administrator. In addition, log files are rotating so any entries will automatically be deleted after a certain amount of time (typically a few months).