Everywhere I look, folks lowercase “is” in titles. I know this is confusing because of all those pesky title capitalization rules.
“Okay, clever clogs, why is ‘is’ capitalized in titles?” you ask. Simple! Because it’s a verb. Capitalize verbs in titles. Unless (there’s always an “unless”) you’re using sentence case (also known as sentence style) for titles, but that’s another kettle of grammar guppies.
Read what my favorite grammarian, Mignon Fogarty (Grammar Girl) has to say about capitalizing words in titles. As Fogarty states, “There’s nothing special about the verb “is.” Sorry, little guy.