The fretboard below show the notes for a Standard Guitar when "Open D" is used. The strings are tuned to the following notes:
D2A2D3F♯3A3D4
For other alternatives see the available tunings for Standard Guitar
The tuner is fully chromatic but if you need a reference of a specific tuning when tuning by ear or if you want to tune any other instrument follow the steps in how to setup the guitar tuner for other instruments