step-by-step vs bit-by-bit

step-by-step and bit-by-bit both are adjectives.

Word	Noun	Adjective	Verb	Adverb
step-by-step	No	Yes	No	No
bit-by-bit	No	Yes	No	No

As adjectives, step-by-step and bit-by-bit are synonyms defined as:

Other synonyms of step-by-step include in small stages, piecemeal, stepwise.

step-by-step (adjective)	bit-by-bit (adjective)
one thing at a time	one thing at a time