The tuner pedal should go first in the effect signal chain. This is to allow the cleanest signal into the pedal for viewing the most accurate tuning pitch. Positioning the tuner pedal after other effects (distortion, modulation, EQ pedals, etc) can distort the notes in the signal affecting pitch accuracy.
Where does the Fuzz go in a pedal chain?
Generally, your distortion, overdrive and fuzz effects pedals should go towards the start of your pedal chain as they have the greatest effect on the tone. Fuzz pedals should usually go first, followed by overdrive and finally distortion.
How do you connect a tuner pedal?
Put your tuner pedal first in the chain.
If you use a tuner pedal, it needs the raw sound directly from your guitar to keep your guitar in tune. For this reason, it should always go first in your chain and connect directly to your guitar. If you put it after another pedal, it won't tune your guitar properly.