vietphonics.com

Vietphonics is a free website to help you hear Vietnamese (Northern dialect) sounds — the tones, vowels, diphthongs and consonants that are hard to tell apart with an English-tuned ear.

It plays short audio clips drawn from minimal pairs and asks you to pick what you heard. Under the hood it’s a spaced-repetition system (SRS): it tracks which sounds and contrasts you get wrong and keeps resurfacing them, so you spend your time on the ones you actually struggle with.

Try it at vietphonics.com.