How to Write a Product Requirements Document (PRD)

What a PRD actually is (and what it isn't)

A product requirements document is a written description of what you want to build and why. It sits between the idea in your head and the code a developer writes. Its job is simple: make sure everyone touching the product, you, the designer, the engineer, the freelancer in another city, all share the same picture of what's being built.

It is not a legal contract, a 40-page spec, or a place to dump every feature you've ever dreamed up. The biggest mistake founders make is treating the PRD like a wishlist. A PRD that tries to describe everything ends up guiding nothing. The best ones are short, sharp, and ruthless about what's in and what's out.

If you're still deciding whether you even need a full product versus a quick test, it's worth understanding the difference between an MVP, a prototype, and a proof of concept first. A PRD is most useful once you've decided to build something real that people will use.

Start with the problem, not the feature

Every weak PRD I've seen opens with a solution: "We need a dashboard with filters and export." Every strong one opens with a problem: "Our users can't tell which orders are delayed, so they call support, which costs us time and frustrates them."

When you lead with the problem, the developer understands the why. That matters more than you'd think. A developer who understands the why will make a hundred small decisions correctly without asking you. A developer who only has a feature list will build exactly what you wrote, even when what you wrote was slightly wrong.

Write the problem in plain language. Who has it, when does it happen, what does it cost them today, and what do they do instead right now. If you can't describe the problem clearly, no amount of feature detail will save the build.

The core sections every PRD needs

You don't need a fancy template. A clean document with these sections covers almost any product or feature. Add or drop sections based on what the team actually needs to know.

• Problem and goal: what hurts today, and what "better" looks like in one or two sentences.
• Target user: who this is for, described specifically. "Small clinic receptionists who book appointments by phone" beats "users."
• Scope: a short list of what's in this version, and an explicit list of what's out. The out list is just as important.
• User flows: the steps a person takes to get value, written as a sequence. Not screen designs, just the path.
• Requirements: the specific things the product must do, written as plain statements.
• Success metrics: how you'll know it worked. Could be a number, could be a behaviour you expect to see.
• Open questions: things you haven't decided yet, written down so they don't get forgotten.

Write requirements people can actually verify

A requirement should be checkable. "The app should be fast" is not a requirement; it's a hope. "A search result should appear within two seconds on a normal mobile connection" is something a developer can build toward and you can test.

Write each requirement as a clear statement of what the system does from the user's point of view. A useful pattern is: as a [type of user], I want to [do something], so that [outcome]. This keeps you honest about who benefits and why. You don't have to use that exact phrasing everywhere, but the discipline behind it, naming the user and the outcome, is what makes requirements usable.

Separate the must-haves from the nice-to-haves explicitly. If everything is a priority, nothing is. When you're forced to cut scope to hit a deadline or budget, this separation is what saves you from cutting the wrong thing. For a deeper method on this, see how to prioritise the features in your MVP.

Describe flows, not screens

Founders often jump straight to describing pixels: "the button should be blue, top right." Leave that to the designer. In the PRD, your job is to describe the flow, the sequence of steps a user moves through to get something done.

Take a simple example: a user signs up, verifies their phone over OTP, lands on an empty dashboard, adds their first item, and sees it appear in a list. That sequence tells a developer far more than a static screenshot does. It reveals the states you need to handle, the empty state, the loading state, the error when the OTP fails.

Most bugs and rework come from states nobody thought about. What happens when there's no data yet? When the payment fails? When the user loses connection halfway? Walking through the flow surfaces these questions early, while they're cheap to answer.

1. Pick the single most important thing a user does in your product.
2. Write each step they take, from entry to the moment they get value.
3. For each step, ask: what could go wrong here, and what should happen then?
4. Note the empty, loading, error, and success states for the key screens.
5. Repeat for the next most important flow, and stop once the core is covered.

Keep it short and keep it living

A PRD for an MVP or a single feature should usually fit on a few pages. If it's growing past that, you're probably either building too much at once or writing detail that belongs in design or code. Length is not a sign of quality. Clarity is.

Treat the document as living, not final. You will learn things once people start building and once real users touch the product. When you change your mind, change the PRD, and tell the team what changed and why. A stale PRD that everyone has stopped reading is worse than no PRD at all, because it creates false confidence.

Tools matter less than people think. A shared Google Doc, a Notion page, or a single markdown file all work fine. What matters is that there's one source of truth everyone can find, and that it's actually kept up to date. This becomes especially important once you're managing a software project with more than one person involved.

Common mistakes that quietly wreck the build

The PRD itself is rarely where projects fail. They fail in the gap between what was written and what was understood. A few patterns show up again and again.

• Describing solutions instead of problems, so the team can't course-correct.
• No 'out of scope' section, so scope quietly grows until the budget runs out.
• Vague requirements nobody can test, leading to "that's not what I meant" at delivery.
• Ignoring edge cases and error states, which become the bulk of last-minute bugs.
• Writing it once and never updating it, so the document and the product drift apart.
• Mixing the PRD with the contract or the budget, which makes people defensive instead of collaborative.

A simple PRD you can copy today

If you want a starting point, open a blank document and write these headings, then fill each with two or three plain sentences. Problem. Who it's for. Goal. In scope. Out of scope. Main user flow. Requirements (must-have vs nice-to-have). Success looks like. Open questions.

That's it. Resist the urge to make it fancy. A founder who can fill those nine headings honestly understands their product better than one with a beautiful 30-page document full of features they'll never build. Share it with whoever is building, read it together once, and let them ask questions. The questions they ask will tell you exactly where your thinking is still fuzzy.