adverb
Adverb meaning 'on every occasion' or 'whenever something happens'. Often used with verbs of change or repetition.
会う度ごとに彼は新しい話をしてくれる。
Every time I meet him, he tells me a new story.
このアプリは開く度ごとに更新される。
This app updates every time you open it.
Also means 'each time', but 度に is a conjunction-like phrase (e.g., 会う度に), while 度ごと is an adverb that can stand alone or modify a verb directly.
Compound of 度 (たび, 'time, occasion') and ごと ('each, every').