Canon M has a 18.0MP APS-C (22.3 x 14.9 mm ) sized CMOS sensor and features Digic 5 processor. You can shoot at maximum resolution of 5184 x 3456 pixels. M has a native ISO range of 100 - 12800 which can be boosted to 25600 and it can save files in RAW format which gives you a wider room for post processing.
Canon M is not the highest resolution APS-C camera. Fujifilm X-E5 with its 40.0MP sensor is leading in this class. Check the comparison of Canon M vs Fujifilm X-E5 or take a look at Highest resolution Mirrorless cameras list.
Canon M DxOMark Sensor Scores
DxOMark is a benchmark that scientifically assesses image quality of camera sensors. Canon M sensor has been tested by DxO Mark and got an overall score of 65 for its image quality. You can find the details of their analysis of Canon M here.
Let's look at how the size of the Canon M's APS-C sensor compares with other standard sensor sizes.
Comparison image of Canon M Sensor Size with other standard sensors
Sensor size is what determines the circle of confusion, and therefore how much
depth of field Canon M gives you at any given aperture.
You can
calculate
the exact depth of field for the Canon M
at any focal length, aperture and subject distance, including the hyperfocal distance
for landscapes and the very shallow focus zone you get with long telephoto lenses.
