Marty Cagan's Four Big Product Risks, and How to Test Each One

Marty Cagan's four big risks are value, usability, feasibility and viability. Before you build, ask whether customers will choose it, whether they can work out how to use it, whether you can build it and whether it works for the rest of the business.

Most failed products ignored one of the four. The trick is to find out which one is riskiest for your idea and test it first.

What the Four Big Risks Are

Marty Cagan describes the four risks in his book Inspired. They're the heart of his view of product discovery: the work of finding out what's worth building before you commit to building it.

• Value risk: will customers buy it, or choose to use it?
• Usability risk: can users work out how to use it?
• Feasibility risk: can our engineers build it with the time, skills and technology we have?
• Viability risk: does this solution work for the various parts of our business, such as legal, finance, sales and brand?

Cagan argues that empowered product teams own all four risks together. The product manager is especially accountable for value and viability, the designer for usability and the tech lead for feasibility.

When to Choose the Four Big Risks

Choose it when you're about to build and want to know which risk could sink the idea. It's also a useful check when:

• a team has tested usability thoroughly but never asked if anyone wants the product
• engineering is unsure whether something can perform at scale
• a launch might clash with a contract, a regulation or the brand
• stakeholders are pushing for a build with no discovery at all

How to Use the Four Big Risks, Step by Step

1. Describe the idea in a sentence. Who it's for and what it does.
2. Write down what you believe for each risk. For example, "Customers will pay £5 a month for this" is a value belief.
3. Rate your confidence in each. Be honest. Gut feel doesn't count as evidence.
4. Pick the riskiest one. Start with the risk you're least sure about, not the one you're most comfortable testing.
5. Choose a quick test. Value risks suit fake door tests, customer letters or concierge tests. Usability risks suit prototypes and usability testing. Feasibility risks suit a feasibility prototype or spike. Viability risks need conversations with legal, finance, sales or marketing.
6. Run the test and record what you learned.
7. Repeat for the next riskiest risk. Keep going until you're confident enough to build.

A Worked Example

Imagine a coffee chain planning a loyalty feature in its app. Regular customers would earn points towards free drinks at partner bakeries nearby.

The team assessed the four risks.

• Value: a quick survey and a fake door in the app showed strong interest. Evidence was good.
• Usability: five usability sessions with a clickable prototype went smoothly after one small fix. Evidence was good.
• Feasibility: engineers needed to connect to each bakery's till system. That was uncertain, so they built a small spike with one bakery. It worked.
• Viability: nobody had asked legal. When they did, it turned out an existing partnership contract gave another brand exclusive rights to joint loyalty schemes in the region.

The idea that looked ready to build had a viability problem that would have stopped it at launch. Because they checked early, the team reshaped the idea around in-store rewards and avoided months of wasted work.

Common Mistakes

Testing the Comfortable Risk

Designers often start with usability and engineers with feasibility. Start with the risk you understand least.

Leaving Viability Until the End

Legal, finance and brand concerns surface late and expensively. Bring those colleagues in early.

Treating Opinions as Evidence

A senior stakeholder saying customers will love it is a belief, not proof. Test it.

Separating Discovery from Delivery

The four risks work best when the same team that builds the product also does the discovery. Hand-offs lose learning.

How It Compares with Related Tools

Assumption mapping goes deeper. It lists every belief behind an idea and plots them by importance and evidence.

The opportunity assessment is a short set of questions to answer before committing a team. It pairs well with the four risks.

Fake door tests, prototypes and concierge tests are the practical ways to reduce each risk quickly.

A pre-mortem asks the team to imagine the product has failed and explain why. It often surfaces viability risks nobody mentioned.

Quick Tests for Each Risk

Most risks can be reduced in days rather than months. Here are some starting points.

• Value: customer interviews, a customer letter, a fake door test or a concierge test.
• Usability: a paper prototype, a clickable user prototype and a few usability sessions.
• Feasibility: a feasibility prototype or short technical spike, ideally with the engineers who'll build it.
• Viability: a short conversation with legal, finance, sales, support or marketing, using a prototype so they can see it.

The aim isn't certainty. It's enough confidence to make a good decision about whether to build, change course or stop.

Write down what you learned from each test, even when the answer is disappointing. A short record of tested risks makes it much easier to explain a decision to stakeholders later. It also stops the same idea returning six months on with nobody remembering why it was dropped.

Bringing It Together

The four big risks are a simple discipline: before you build, know which risk could sink you and test it first. Teams that do this ship fewer things that nobody wants. The Product Field Kit includes a fillable four big risks worksheet so your team can rate each risk and plan the right tests.

Questions People Ask

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