Of Or On? (I will keep you posted of/on the progress)

[Woewoe]

hi there. just want to confirm which is correct.

I will keep you posted of the progress

I will keep you posted on the progress

Thanks.

[Milanya]

BYU-BNC: BRITISH NATIONAL CORPUS
on -2
of -0
CORPUS OF CONTEMPORARY AMERICAN ENGLISH
on - 59
of -1

"On" is probably correct.
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con·text - The part of a text or statement that surrounds a particular word or passage and determines its meaning.