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lucia-auth/lucia

★ 10,466Audience · developerComplexity · 2/5Setup · easy

TLDR

Lucia is now a learning resource that teaches JavaScript and TypeScript developers how to build their own session-based authentication from scratch, having shifted away from being an installable library because one-size-fits-all auth is too hard to maintain.

Mindmap

mindmap
  root((lucia))
    What it is
      Auth learning resource
      Deprecated library
      Free guides site
    Teaches you
      Session management
      User identity
      Database-backed auth
    Related projects
      Oslo utilities
      Arctic OAuth client
      Copenhagen Book
    Audience
      JS TS developers
      Framework agnostic
      Any database
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Things people build with this

USE CASE 1

Learn how to implement session management and user sign-in from scratch for a JavaScript web app without relying on a third-party library

USE CASE 2

Use the Oslo utility packages for cryptography and session tokens as small focused building blocks in your own auth layer

USE CASE 3

Integrate the Arctic OAuth 2.0 client to add Google or GitHub sign-in to an app while keeping full control of session handling

Tech stack

TypeScriptJavaScript

Getting it running

Difficulty · easy Time to first run · 1h+

No library to install, read the guides at lucia-auth.com and implement session authentication yourself using your chosen database and framework.

License not specified in the explanation.

In plain English

Lucia started as an authentication library for JavaScript and TypeScript applications, but has since changed direction. As of early 2025, the library version (v3) is deprecated and the project now serves as a learning resource rather than installable software. Authentication is the part of a web application that handles user sign-in, sessions, and identity. Rather than providing code you install as a dependency, the Lucia project now teaches developers how to implement these features themselves from scratch. The site at lucia-auth.com walks through building session management using your own database, framework, and libraries of choice. The reason the project moved away from being a library is explained in the README: the authors found it very difficult to build a single library that works well across the many database systems, web frameworks, runtimes, and deployment environments that JavaScript developers use. They concluded it is more practical to teach the underlying concepts and a straightforward implementation that each developer can then adapt to their specific setup. Related projects are linked from the repository. The Copenhagen Book is a free online guide covering web application authentication concepts broadly. Oslo is a set of small, focused utility packages for authentication and cryptography. Arctic is an OAuth 2.0 client library, which handles the flow for signing in users through third-party providers like Google or GitHub. Developers who were using Lucia v3 are directed to the announcement post for migration guidance. The source code for v3 remains available on a separate branch.

Copy-paste prompts

Prompt 1
Walk me through building a session-based login system for a Node.js app from scratch using the approach described in the Lucia guides, with a PostgreSQL database
Prompt 2
Show me how to use the Arctic library to implement GitHub OAuth sign-in and store the resulting session in my own database table
Prompt 3
Using the Oslo packages, generate a cryptographically secure session token, hash it for storage, and verify it on each request
Prompt 4
I was using Lucia v3, walk me through migrating my authentication code to a custom session implementation following the new Lucia guides
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