They're all canon, but the real question comes as non-filler.
Usually a filler is an episode in which nothing important happens, so no reoccurring characters are turn up, no semi-important battle happens, no one in the main cast or their rivals catches a new pokemon and none of their pokemon either evolves, learns a new move or masters a new move.
So for example, "Cerulean Blue" is not a filler episode because Misty obtains a Gyarados, however, "A Date with Delcatty" can be considered filler because even though Casey and Misty both appear, nothing all that notable happens.