honest-to-goodness vs honest-to-god

honest-to-goodness and honest-to-god both are adjectives.

Word	Noun	Adjective	Verb	Adverb
honest-to-goodness	No	Yes	No	No
honest-to-god	No	Yes	No	No

As adjectives, honest-to-goodness and honest-to-god are synonyms defined as:

honest-to-goodness and honest-to-god: (used informally especially for emphasis) real or genuine

Other synonyms of honest-to-goodness include sure-enough.

honest-to-goodness (adjective)	honest-to-god (adjective)
(used informally especially for emphasis) real or genuine	(used informally especially for emphasis) real or genuine