This One File Controls Everything in Claude

There's a single file that controls how Claude behaves in every conversation, and most people don't even know it exists.

It's called CLAUDE.md. A markdown file that lives inside your workspace folder. Claude reads it at the start of every session, before you even type a word. (Imagine an employee who reads the onboarding doc every single morning without being asked. That's this file.)

Here's the 30-second version:

What Goes In It

Who you are. What you do. Your rules. Your preferences. "Always write in a casual tone." "I run a marketing agency with 12 clients." "Never touch production without asking."

Once Claude reads that, it doesn't need you to repeat yourself. Every conversation starts with full context on you and your work, instead of you re-explaining your life story for the hundredth time.

One File Per Project

I have different CLAUDE.md files for different projects. My content project knows I run a channel, my upload schedule, my voice. My business project knows my pricing and services. Neither one wastes my time asking questions the file already answers.

Set it up once. It changes every conversation you'll ever have.

This is part 2 of my 20-part Cowork series. The full breakdown of all 20 concepts is in the complete guide.

Open your workspace folder and create the file tonight. Ten minutes, permanent payoff.