How to Write a Software Requirements Document
The quality of your requirements document directly determines the quality of your software. Here's how to write one that actually works.
Most software projects fail not because of bad code, but because of bad requirements. Vague specifications, unstated assumptions, and scope that shifts mid-build are responsible for more wasted development dollars than any technical challenge.
A good software requirements document (SRD) bridges the gap between what stakeholders envision and what developers build. It doesn't need to be a 100-page waterfall document — in fact, shorter is usually better. It needs to be specific, testable, and agreed-upon.
What a Requirements Document Should Include
A practical SRD covers six areas: project overview (the "why"), user roles and personas (the "who"), functional requirements (the "what"), non-functional requirements (the "how well"), constraints and assumptions, and acceptance criteria (the "done definition").
The project overview should be one paragraph that anyone in your company can understand. If you can't explain what you're building and why in 3 sentences, you don't have clarity yet.
Project Overview
Business context, problem being solved, success metrics, and key stakeholders. One page maximum.
User Roles
Who uses the system? What are their goals? What's their technical comfort level? Include edge cases.
Functional Requirements
Specific, testable statements about what the system does. "Users can filter orders by date range" not "the system should have good search."
Non-Functional Requirements
Performance targets, security requirements, accessibility standards, and scalability expectations — with specific numbers.
Writing Requirements That Developers Can Build
The most common mistake in requirements is ambiguity. "The system should be fast" means nothing. "Search results return within 200ms for queries against up to 1 million records" is buildable, testable, and measurable.
Every requirement should pass the "could a QA engineer write a test for this?" check. If the answer is no, the requirement is too vague. Break it down until each statement is specific enough to verify objectively.
Prioritize ruthlessly. Mark every requirement as must-have, should-have, or nice-to-have. The must-haves define your MVP — if you only build those, would the software be useful? If not, you're missing requirements or prioritizing wrong.
Common Mistakes to Avoid
Describing solutions instead of problems: "Add a dropdown menu with options A, B, C" prescribes a solution. "Users need to select from 3 predefined categories" describes the need. Let developers propose the best implementation.
Scope creep through "and also" additions: Every stakeholder meeting will produce new ideas. Capture them, but don't add them to the current scope without removing something else. Requirements documents should have a "parking lot" for future features.
Ignoring edge cases: What happens when the database is empty? When a user enters special characters? When two people edit the same record simultaneously? Edge cases are where most bugs live.
Templates and Formats
We recommend a structured document with these sections: Executive Summary (1 page), User Stories grouped by feature area, Technical Requirements (performance, security, infrastructure), and Acceptance Criteria per user story.
User stories work well as the core format: "As a [role], I want to [action] so that [benefit]." Each story gets acceptance criteria that define when it's complete. This format is universally understood by developers and keeps requirements user-focused.
Frequently Asked Questions
How detailed should requirements be?
Should we use user stories or traditional requirements?
How do we handle changing requirements?
Do we need a requirements document for an MVP?
Need Help Defining Requirements?
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