Standard reentrant tuning: G4, C4, E4 and A4. Reentrant means the G is the high one rather than the low one, which is what gives the ukulele its sound and what makes tuning it by comparison to a guitar confusing.
Fork shows the string you are nearest and how many cents off you are, so there is no need to work out which of the four you have just plucked.
Common questions
Is it free?
Yes. No signup, no account, no paid tier.
Does it record me?
No. Pitch detection runs in your browser and the audio never leaves your device.
Can I tune to A = 432 Hz?
Yes. Reference pitch adjusts from 430 to 450 Hz under settings, with 432 and 440 as
presets.
Why does it need my microphone?
A tuner works by listening. Your browser will ask the first time you press start.