"mä" can stand for "minä" in spoken Finnish. The sentence decides its meaning.
These are common spoken alternatives to minä. Which form you hear varies by speaker and situation.
mä, mää, mnää, mie, miä
These are related spoken alternatives. Which one you hear varies by speaker and situation. Check each example rather than treating them as interchangeable in every sentence.
Moi! Mä oon Anna. - Hi! I'm Anna.
mä here: I - spoken form of 'minä'
Written Finnish: Hei! Minä olen Anna.
Anteeks, mä en ymmärrä. - Sorry, I don't understand.
mä here: I - spoken form of 'minä'
Written Finnish: Anteeksi, minä en ymmärrä.
Mä otan kahvin, kiitos. - I'll have a coffee, please.
mä here: I - spoken form of 'minä'
Written Finnish: Minä otan kahvin, kiitos.
Saisinks mä yhen pullan? - Could I get one pulla?
mä here: I - spoken form of 'minä'
Written Finnish: Saisinko minä yhden pullan?
Voinks mä maksaa kortilla? - Can I pay by card?
mä here: I - spoken form of 'minä'
Written Finnish: Voinko minä maksaa kortilla?
Mä asun Helsingissä. - I live in Helsinki.
mä here: I - spoken form of 'minä'
Written Finnish: Minä asun Helsingissä.
Spoken and written Finnish are different registers. The examples show how "mä" is used here and pair it with the written sentence. Learn the meaning in context rather than replacing every occurrence of a word.