How to Write a Technical Specification for Your App (Without Being a Developer)

What Makes a Good Specification

User Story Template

## User Story Format

As a [type of user]
I want to [perform an action]
So that [I achieve a benefit]

## Example

As a customer
I want to save my payment method
So that I can checkout faster next time

## Acceptance Criteria
- User can add credit/debit card
- Card number is masked (show last 4 digits)
- User can have multiple saved cards
- User can delete saved cards
- User can set a default card

Feature Specification Example

## Feature: User Registration

### Overview
Allow new users to create an account to access the platform.

### User Flow
1. User clicks "Sign Up"
2. User enters email address
3. System validates email format
4. User creates password (8+ characters)
5. System sends verification email
6. User clicks verification link
7. Account is activated

### Requirements
- Email must be unique in system
- Password: minimum 8 characters, 1 number, 1 special character
- Verification link expires in 24 hours
- User can resend verification email

### Edge Cases
- What if email already exists? Show "email already registered" with login link
- What if verification link expires? Allow resend
- What if user never verifies? Account remains inactive

Data Requirements Template

## User Profile Data

### Required Fields
- Email (unique, used for login)
- Password (hashed, never stored in plain text)
- Full Name
- Account Created Date

### Optional Fields
- Phone Number
- Profile Photo
- Address (for shipping)

### Business Rules
- Email cannot be changed after registration
- Password can be reset via email
- Account can be deactivated but not deleted (for records)

Common Mistakes to Avoid