C blues scale
C E♭ F G♭ G B♭
Formula: 1 ♭3 4 ♭5 5 ♭7
The minor pentatonic with the ♭5 added: the blue note, usually played in passing between the 4th and the 5th.
On the neck, frets 0 to 12
The 1st string (high e) is at the top, as in the app. The root is filled.
Open it in the app: 3. Scales & Modes, in C
The blues scale in other keys