I REALLY want to do more and improve my jazz improvisation. Saying that for multiple years now...

What is your favorite source for backing tracks?

Ideally it would be really easy to access, doesn't need to be for free.

I have found some nice tracks on Youtube, but interested in how you do it.

iRealPro - costs $20 or so but you can download a playlist of 1350 jazz standards and also make your own backing tracks / edit existing ones.