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Sunaina-ismail
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better-auth

Integrate Better Auth with FastAPI for JWT authentication using a shared secret.

Updated Dec 8, 2025
Search Tags:#security#authentication#fastapi#jwt#nextjs#user isolation
One-click install
npx skills add https://github.com/Sunaina-ismail/todo-hackathon --skill better-auth-sunaina-ismail
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: better-auth
Source: https://github.com/Sunaina-ismail/todo-hackathon/tree/main/.claude/skills/better-auth
Command: npx skills add https://github.com/Sunaina-ismail/todo-hackathon --skill better-auth-sunaina-ismail

SYSTEM DOCUMENTATION & REQUIREMENTS

💡 This Skill includes references (resource) components.

What problem does it solve?

This Skill streamlines the implementation of secure authentication between a Next.js frontend and a FastAPI backend by leveraging a shared secret for JWT tokens, ensuring robust user data isolation and preventing unauthorized access.

Core Features & Use Cases

  • Shared Secret JWT: Implements HS256 symmetric encryption for JWTs, using a single BETTER_AUTH_SECRET for signing and verification across frontend and backend.
  • User Data Isolation: Enforces that users can only access and modify their own data by validating the user_id from the JWT against the user_id in API requests.
  • Use Case: Securely authenticate users in a todo application, ensuring that User A cannot view or modify User B's tasks.

Quick Start

Configure Better Auth in Next.js and FastAPI using the BETTER_AUTH_SECRET environment variable.

Frequently Asked Questions about better-auth

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I implement JWT authentication between Next.js and FastAPI?▼

JWT authentication between Next.js and FastAPI is implemented here using a shared BETTER_AUTH_SECRET to sign and verify tokens with the HS256 algorithm. This manages token flow and validation across the frontend and backend.

How does JWT validation enforce user data isolation in FastAPI?▼

User data isolation is enforced by validating the user_id extracted from the JWT against the user_id in each API request. This prevents users from accessing or modifying data belonging to other users.

Can I use a shared secret for JWT signing across a Next.js frontend and FastAPI backend?▼

Yes, you can use a shared secret for JWT signing across Next.js and FastAPI. The implementation uses the BETTER_AUTH_SECRET environment variable for HS256 symmetric encryption to verify tokens on both ends.

What is the best way to secure a todo application with FastAPI and Next.js?▼

Securing a todo application is achieved by integrating Better Auth to manage JWT token flow and validation. This ensures robust user data isolation so users can only access their own tasks.

Do I need an asymmetric algorithm for JWT validation between Next.js and FastAPI?▼

No, you do not need an asymmetric algorithm. This implementation uses the HS256 symmetric encryption algorithm with a single shared BETTER_AUTH_SECRET to handle JWT signing and verification.

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