Co-Founder can be used as a title while Co-founder (founder is not capitalized) can be used when you want to begin a sentence. For example, a Co-founder is the same thing as a joint founder.
How do you write co-founder?
If using a hyphenated spelling of the word, it is generally recommended to use “Co-founder” rather than “Co-Founder”. When not attempting to start a sentence or identify a title, however, the word can just be spelled as “cofounder” or “co-founder”.
Is co-founder capitalized in AP style?
Rhonda Shafer MoralesAP Stylebook
A title following a name is lowercase in AP Style. But co-founder is rarely a formal title, more a descriptive and lowercase even preceding a full name.
