Fujifilm X-Pro1 has a 16.0MP APS-C (23.6 x 15.6 mm ) sized CMOS X-TRANS I sensor and features EXR Pro processor. You can shoot at maximum resolution of 4896 x 3264 pixels with aspect ratios of 1:1, 3:2 and 16:9. X-Pro1 has a native ISO range of 100 - 6400 which can be boosted to 25600 and it can save files in RAW format which gives you a wider room for post processing.
Fujifilm X-Pro1 is not the highest resolution APS-C camera. Canon M6 MII with its 33.0MP sensor is leading in this class. Check the comparison of Fujifilm X-Pro1 vs Canon M6 MII or take a look at Highest resolution Mirrorless cameras list.
Another important feature about Fujifilm X-Pro1's sensor is the lack of anti-alias (Low-pass) filter. Removing anti-aliasing filter increases the sharpness and level of detail but on the other side it also increases the chance of moire occurring in certain scenes.
Let's look at how the size of the Fujifilm X-Pro1's APS-C sensor compares with other standard sensor sizes.