The original version of this document is located at at https://docs.qfield.org/how-to/pg-service
A pg_service.conf file allows to use an named alias for a PostgreSQL server connection. Instead of storing hostname, port, database name and more into the QGIS Project file, these can be stored separately. It is even possible to store username and password in a pg_service.conf file, to avoid having this stored in clear text in the QGIS Project.
Read more about PostgreSQL services in the QGIS documentation.
If you directly connect from QGIS to your database you can make use of a pg_service.conf file by placing it in the QField data folder. You can place your file either on the Internal Device Storage or on the SD Card Storage. You can check the path for the QField data folder in the bottom of the About QField screen in the app.
Usually the path on Android devices looks something like this: /Android/data/ch.opengis.qfield/files/QField.
!!! note
Unlike on *NIX systems where the file is named .pg_service.conf, the file on Android is named pg_service.conf without a leading dot sign (.).
QFieldCloud support pg_service.conf configurations too. You need to configure your PostgreSQL layers with "Offline editing" cloud action and store your service settings on QFieldCloud Project's Secrets page.
Read more how to configure PostgreSQL service in the QFieldCloud documentation.