It'll is a contraction of the words “it will.” When you squeeze two words together and replace some letters with an apostrophe, you create a contraction. In this case, the apostrophe replaces the letters “w” and “i” in “will.”

People use it'll in everyday speech and informal writing because it flows more naturally than saying both words separately. You might say “It'll be fun” instead of “It will be fun,” or “It'll take about an hour” instead of “It will take about an hour.” The meaning stays exactly the same, but the contraction sounds more relaxed and conversational.

You'll see it'll often in dialogue in stories, in text messages, and in casual emails. However, in formal writing like research papers or business letters, writers usually spell out both words: “it will.” Understanding when to use contractions and when to avoid them is part of learning to match your writing style to your audience and purpose.