A design rationale document captures the "why" behind design decisions—the context, constraints, alternatives considered, and reasoning that led to a particular solution. While designs themselves show what was built, rationale documents preserve institutional knowledge about why it was built that way.
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---
name: develop-design-rationale
description: Documents the reasoning behind design decisions including alternatives considered, trade-offs evaluated, and principles applied. Use when making significant UX decisions, aligning with stakeholders on design direction, or preserving design context for future reference.
phase: develop
version: "2.0.0"
updated: 2026-01-26
license: Apache-2.0
metadata:
category: specification
frameworks: [triple-diamond, lean-startup, design-thinking]
author: product-on-purpose
---
# Design Rationale
A design rationale document captures the "why" behind design decisions—the context, constraints, alternatives considered, and reasoning that led to a particular solution. While designs themselves show what was built, rationale documents preserve institutional knowledge about why it was built that way.
## When to Use
- When making significant UX decisions that affect user experience
- Before design reviews to prepare stakeholder discussions
- When multiple valid approaches exist and the choice needs justification
- To onboard new team members to existing design decisions
- When revisiting past decisions to understand original reasoning
- During design system evolution to document pattern choices
## Instructions
When asked to document design rationale, follow these steps:
1. **State the Decision**
Begin with a clear, one-sentence summary of what design decision was made. This becomes the title and reference point for the document.
2. **Describe the Context**
Explain the situation that prompted this decision. What problem were you solving? What constraints existed? What user needs informed the direction? Include relevant research findings.
3. **List Options Considered**
Document at least 2-3 alternatives that were evaluated. For each option, describe what it would look like and its key characteristics. Be fair to all options—avoid strawmen.
4. **Define Evaluation Criteria**
Specify how options were assessed: usability heuristics, technical feasibility, brand alignment, user research findings, business requirements, or design principles.
5. **Explain the Reasoning**
Walk through why the chosen option best meets the criteria. Be explicit about trade-offs—what you gained and what you sacrificed. Acknowledge where the decision is reversible vs. irreversible.
6. **Document Trade-offs Accepted**
Every design decision involves trade-offs. Name what you gave up and why it was acceptable. This honesty helps future teams understand constraints.
7. **Note Follow-up Considerations**
Capture anything that needs attention later: metrics to watch, conditions that might warrant revisiting the decision, or related decisions to make.
## Output Format
Use the template in `references/TEMPLATE.md` to structure the output.
## Quality Checklist
Before finalizing, verify:
- [ ] Decision is clearly stated in one sentence
- [ ] Context explains the "why now" and constraints
- [ ] Multiple alternatives are documented fairly
- [ ] Evaluation criteria are explicit
- [ ] Reasoning addresses why chosen option beats alternatives
- [ ] Trade-offs are honestly acknowledged
- [ ] Document is useful to someone inheriting this design
## Examples
See `references/EXAMPLE.md` for a completed example.
