When do I use "it's" with an apostrophe?

Contexti

The apostrophe in it's stands in for a missing letter — the i of is or the ha of has. That's the same logic as don't (do not) or she'll (she will). Once you read the apostrophe as a "something is missing here" sign, the rule becomes obvious.

A little moreii

It's raining unpacks to it is raining. It's been a while unpacks to it has been a while. If the unpacking breaks the sentence ("the dog wagged it is tail"), you want the possessive its.

Examplesiii

Watch foriv

The full entryv

More quick answersvi

• → Is "its" or "it's" the possessive? Its (no apostrophe) is the possessive. It's (with apostrophe) is short for "it is."
• → Is it "its a dog" or "it's a dog"? "It's a dog." The phrase is a contraction of "it is" — the apostrophe belongs.