Langfa.st vs. Lucia Auth
Langfa.st
Langfa.st is a fast and minimal playground for testing and refining AI prompts. It supports over 50 large language models, including OpenAI, Anthropic, Mistral, Cohere, Google, and others — all available instantly without setup. You can insert variables, use Jinja2 templating, and compare outputs across models. There’s no need to sign up or bring your own API keys — it works out of the box. Langfa.st was built to eliminate the friction of existing tools: complicated UIs, required credentials, or overpriced subscriptions. It gives AI teams and prompt engineers a clean, disposable space to experiment, debug, and iterate — all in one tab. Free to use. You only pay if you need more volume or power features.
Lucia Auth
Lucia is an open source auth library that abstracts away the complexity of handling sessions. It works with any JS runtime - Node.js, Bun, Deno, Cloudflare Workers. It's also fully typed. It integrates with MongoDB. PostgreSQL, MySQL, SQLite, and with their respective ORMs and query builders.
Reviews
Reviews
| Item | Votes | Upvote |
|---|---|---|
| Works without login or API key | 1 | |
| Supports 50+ models out of the box | 1 | |
| Built-in support for variables and Jinja2 templating | 1 | |
| Instant response, no setup required | 1 | |
| Clean and distraction-free UI | 1 |
| Item | Votes | Upvote |
|---|---|---|
| No custom API key support (yet) | 1 | |
| Not ideal for running complex multi-turn chats | 1 |
| Item | Votes | Upvote |
|---|---|---|
| Open source | 1 | |
| Fully typed | 1 | |
| Work with any JS runtime | 1 |
| Item | Votes | Upvote |
|---|---|---|
| No cons yet, would you like to add one? | ||
Frequently Asked Questions
Langfa.st is primarily a playground for testing AI prompts and does not focus on authentication, while Lucia Auth is specifically designed as an authentication library that simplifies session management across various JavaScript runtimes. If your goal is to implement authentication, Lucia Auth is the better choice.
Langfa.st is designed for quick AI experimentation with a clean and distraction-free UI, allowing users to test prompts without any setup or login. Lucia Auth, while user-friendly for developers, is more focused on backend authentication processes and may not provide the same level of immediate usability for AI testing as Langfa.st.
Yes, Langfa.st offers features specifically tailored for AI prompt testing, such as support for over 50 language models, built-in variable support, and Jinja2 templating. Lucia Auth, on the other hand, is focused on authentication and does not provide features for AI prompt testing.
Lucia Auth is versatile in that it works with any JavaScript runtime and integrates with multiple databases, making it suitable for a wide range of applications. Langfa.st, while versatile for AI prompt testing, does not cater to authentication needs, which limits its versatility for developers focused on backend solutions.
Langfa.st is a fast and minimal playground for testing and refining AI prompts. It supports over 50 large language models, including OpenAI, Anthropic, Mistral, Cohere, Google, and others — all available instantly without setup. Users can insert variables, use Jinja2 templating, and compare outputs across models without needing to sign up or provide API keys.
Pros of Langfa.st include: it works without login or API key, supports over 50 models out of the box, has built-in support for variables and Jinja2 templating, provides instant responses with no setup required, and features a clean and distraction-free user interface.
Cons of Langfa.st include the lack of custom API key support at this time and it may not be ideal for running complex multi-turn chats.
Langfa.st is particularly beneficial for AI teams and prompt engineers who need a clean, disposable space to experiment, debug, and iterate on AI prompts without the friction of complicated UIs or required credentials.
Yes, Langfa.st is free to use. Users only pay if they need more volume or access to power features.
Lucia Auth is an open-source authentication library designed to simplify session management. It supports various JavaScript runtimes, including Node.js, Bun, Deno, and Cloudflare Workers, and is fully typed. The library integrates with databases such as MongoDB, PostgreSQL, MySQL, and SQLite, as well as their respective ORMs and query builders.
Pros of using Lucia Auth include being open source, fully typed, and its compatibility with any JavaScript runtime. As of now, there are no user-generated cons listed for Lucia Auth.
