하루 하루 and 매일 매일

My Korean dictionary says they’re the same, but 하루 하루 is more like "day by day” in English, where a condition can change by day. Whereas 매일 매일 is more like  "day after day / daily,” where you repeat things over and over again.  They are used interchangeably often in Korean.

Examples)

하루 하루 좋아지고 있어요: It's/He's/She's getting better day by day.

매일 매일 공부해요: I study day after day.

When 매일 매일 is used as “day by day":

매일 매일 가격이 올라요: The price goes up day by day.