Originally Posted by veganbikes

Not wholly correct as far as all pedals having the same threading but typically these days most adult bikes are 9/16" and many kids bikes are 1/2" but there were other standards and back in the day probably most of which have since bitten the dust. Some pedals also use a 6 or 8 allen key in the back to tighten rather than a flat that would use a 15mm pedal wrench.

Also anything with metal on metal contact use grease!!!!!!! If it is titanium use anti-seize/copper paste. Seized pedals (as well as seatposts) are no fun for anyone to deal with.