PRD Template for Authentication
A complete product requirements document template for building authentication features. Pre-filled with realistic examples for login, signup, OAuth integration, session management, and password recovery — ready to customize for your product.
What makes authentication PRDs different
Authentication is one of the few features where a mistake can be existential. A broken checkout page loses revenue for the day. A broken auth system makes the entire product inaccessible. A security vulnerability in auth puts every user account at risk. This asymmetry means authentication PRDs demand more precision than most feature specs.
The challenge is that authentication sits at the intersection of security engineering, UX design, and compliance. Your security team wants bcrypt with a cost factor of 14 and mandatory 2FA. Your growth team wants one-click Google signup. Your legal team needs GDPR-compliant consent flows. A good auth PRD reconciles these tensions with explicit requirements rather than leaving them for engineers to resolve during implementation.
Most auth PRDs fail in one of three ways: they under-specify security requirements (leaving token lifetimes and hashing algorithms to engineering discretion), they ignore error states (what happens when OAuth fails?), or they do not account for migration (how do existing users transition to the new system?). The template below addresses all three.
Authentication PRD template
Eight sections covering every aspect of an authentication feature — from signup flows to token management to security monitoring. Each section includes authentication-specific guidance and examples.
Problem Statement
Authentication is the gateway to every product. A poorly designed auth system creates friction at the moment of highest intent — when a user has decided to try your product. Drop-off rates during signup and login directly impact acquisition, and security failures can be existential.
Example: "Our current signup flow has a 38% abandonment rate. Users are required to verify email before accessing any features, adding an average of 4.2 minutes to time-to-value. Competitor analysis shows that 3 of 4 comparable products offer social login, which we do not support. Additionally, our password reset flow generates 120+ support tickets per month, with an average resolution time of 6 hours."
Tips
- Quantify signup abandonment rates and where users drop off
- Measure current password reset ticket volume and resolution time
- Identify which authentication methods your target users expect (social login, SSO, passwordless)
- Audit your current session management for security gaps (token expiry, concurrent sessions)
Goals and Objectives
Authentication goals must balance security with usability. Overly strict requirements reduce conversion; overly lax ones create risk. Define clear targets for both dimensions, and specify how you will measure each.
Example: "Primary: Reduce signup-to-first-action time from 4.2 minutes to under 60 seconds by adding Google and GitHub OAuth. Secondary: Reduce password reset support tickets from 120/month to under 20/month by implementing magic link login. Security: Achieve zero credential-stuffing breaches by implementing rate limiting and breached-password detection. Timeline: All changes shipped within 8 weeks."
Tips
- Set separate targets for conversion (signup completion rate) and security (breach incidents)
- Define time-to-value as a primary metric — how fast a new user reaches a meaningful action
- Include a target for reducing auth-related support volume
- Specify compliance requirements upfront (SOC2, GDPR consent, CCPA)
User Stories
Authentication user stories span multiple personas: new users signing up, returning users logging in, administrators managing access, and security teams monitoring for threats. Cover the happy path, error states, and recovery flows for each.
Example: "As a new user, I want to sign up with my Google account so that I can start using the product in one click without creating a new password. Acceptance criteria: Google OAuth completes in under 3 seconds; user lands on the onboarding screen with their name and avatar pre-filled; if the Google email matches an existing account, the accounts are linked automatically."
Tips
- Write separate stories for signup, login, logout, password reset, and account linking
- Include an admin story for managing user sessions (force logout, view active sessions)
- Cover the error case: what happens when OAuth fails, email is already taken, or the magic link expires
- Add a story for session persistence — "As a returning user, I want to stay logged in on my laptop for 30 days"
Functional Requirements
Authentication requirements must be precise about supported methods, token lifetimes, rate limits, and edge cases. Ambiguity in auth requirements leads to security vulnerabilities.
Example: "FR-1: The system must support email/password signup with a minimum password length of 12 characters and must reject passwords found in the Have I Been Pwned breached password database. FR-2: The system must support OAuth 2.0 login via Google and GitHub with PKCE flow. FR-3: Access tokens must expire after 15 minutes; refresh tokens after 7 days. FR-4: After 5 failed login attempts within 10 minutes, the account must be locked for 30 minutes and the user notified via email."
Tips
- Specify exact token lifetimes for access tokens, refresh tokens, and magic links
- Define rate limiting thresholds for login attempts, signup, and password reset requests
- List all supported OAuth providers and specify the OAuth flow (authorization code with PKCE)
- Include requirements for account linking when a user signs up with email then later uses OAuth with the same email
Non-Functional Requirements
Authentication systems must meet high standards for availability, latency, and security. Downtime in auth means no user can access the product. Latency in auth means every user session starts with friction.
Example: "NFR-1: Authentication endpoints must maintain 99.99% uptime, measured monthly. NFR-2: Login and signup requests must complete in under 500ms at p95. NFR-3: All passwords must be hashed with bcrypt (cost factor 12) or Argon2id. NFR-4: All auth endpoints must be served over TLS 1.2+. NFR-5: Session tokens must be stored in HttpOnly, Secure, SameSite=Strict cookies — not localStorage."
Tips
- Specify uptime SLA separately for auth (higher than general product SLA)
- Define password hashing algorithm and cost factor explicitly
- Require HttpOnly cookies for session storage — never localStorage for tokens
- Include CSRF protection requirements for all state-changing auth endpoints
Success Metrics
Measure authentication success across three dimensions: conversion (are users getting in?), security (are bad actors staying out?), and support load (are users getting stuck?).
Example: "Metric 1: Signup completion rate. Baseline: 62%. Target: 85%. Measured via Amplitude funnel. Metric 2: Median login time (click to dashboard). Baseline: 3.1s. Target: under 1.5s. Metric 3: Password reset support tickets. Baseline: 120/month. Target: under 20/month. Metric 4: Credential stuffing attempts blocked. Baseline: not tracked. Target: 100% blocked with zero false positives on legitimate users."
Tips
- Track signup completion rate as a funnel, not just a single number
- Measure time from login click to first authenticated page load
- Monitor auth-related support tickets weekly
- Set up alerting for unusual login patterns (credential stuffing, brute force)
Technical Considerations
Authentication architecture decisions have long-lasting consequences. Choosing between session-based and token-based auth, selecting a provider versus building in-house, and designing the token refresh flow all require careful evaluation.
Example: "We will use an established auth library (Better Auth / Auth.js / Clerk) rather than building from scratch to reduce the attack surface. OAuth state parameters will use cryptographically random values stored server-side. Refresh token rotation will be implemented — each refresh token is single-use and issues a new refresh token on use. Revoked tokens will be stored in a Redis blocklist with TTL matching the token lifetime."
Tips
- Evaluate build vs. buy: auth libraries (Better Auth, Auth.js) vs. managed services (Clerk, Auth0)
- Design the refresh token rotation strategy before implementation
- Plan for token revocation — how will you invalidate all sessions for a user?
- Consider multi-device session management from the start
Risks and Mitigations
Authentication is a high-risk surface. Security failures are public, conversion failures are silent, and migration failures can lock out existing users. Address all three categories.
Example: "Risk: OAuth provider outage makes login impossible for users who only have social login. Likelihood: Medium. Impact: High. Mitigation: Always require an email on file, even for OAuth users, and offer magic link as a fallback login method. Risk: Migration from current password hashing algorithm to Argon2id causes login failures. Likelihood: Low. Impact: High. Mitigation: Re-hash on successful login (lazy migration), keep legacy bcrypt support for 90 days."
Tips
- Plan for OAuth provider outages — always have a fallback login method
- Address the risk of breaking existing user sessions during migration
- Consider the risk of rate limiting blocking legitimate users behind a shared IP (corporate offices)
- Include a rollback plan for every auth change
Related templates
PRD Template for SSO
SAML and OIDC single sign-on requirements for enterprise customers.
View template →PRD Template for Two-Factor Auth
TOTP, SMS, and passkey-based second factor requirements.
View template →PRD Template for User Roles
Role-based access control, permissions, and admin management.
View template →Frequently asked questions
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