What Is a Moat and Why It Matters

The concept

A moat is what protects a business from competition. Warren Buffett borrowed the term from medieval castles: the wider the moat, the harder it is for an enemy to get in. In business, the 'enemy' is a competitor trying to take your customers. A company without a moat can be disrupted. A company with a wide moat holds its position for decades.

Think of it like a loyal customer base — the stronger the relationship, the harder it is for a competitor to take them away.

Why blue can't measure it

Financial scores tell you how healthy a business is right now. A moat tells you whether it'll still be healthy in 10 years. That requires judgment — reading about the industry, understanding what customers actually value, and asking whether a well-funded competitor could replicate what makes the company special. No algorithm can do that for you. It's the part of investing that requires your own thinking.

Types of moats to look for

Brand moat: people pay more just for the name. Switching cost moat: too painful to leave, like someone who has used the same bank for 20 years and can't be bothered to move all their accounts. Network effect moat: the more people use it, the more valuable it gets (think social media). Cost advantage moat: structurally cheaper to operate than anyone else at scale. The strongest companies have more than one type.

The practical workflow

Use blue to filter for companies with B+ scores — that tells you the business is financially healthy today. Then ask one question: does this business have a fence around it? If yes, and the price is reasonable, that's worth researching seriously. A healthy company without a moat is a good business that could become a bad investment if a competitor shows up tomorrow.