LangFast

LangFast

Langfa.st
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About

LangFast is a lightweight prompt testing platform designed for product teams, prompt engineers, and developers working with LLMs. It offers instant access to a customizable prompt playground—no signup required. Users can build, test, and share prompt templates using Jinja2 syntax with real-time raw outputs directly from the LLM, without any API abstractions. LangFast eliminates the friction of manual testing by letting teams validate prompts, iterate faster, and collaborate more effectively. Built by a team with experience scaling AI SaaS to 15M+ users, LangFast gives you full control over the prompt development process—while keeping costs predictable through a simple pay-as-you-go model.

About

Simplify prompt edits, version control, and SDK integration in one place. No more scattered tools or waiting on deployments for changes. Explore features crafted to streamline your workflow and elevate prompt engineering. Manage your prompts and projects in a structured way, with tools designed to keep everything organized and accessible. Dynamically adapt your prompts to fit the context of your application, enhancing user experience with tailored interactions. Seamlessly incorporate prompt management into your current development environment with our user-friendly SDK, designed for minimal disruption and maximum efficiency. Leverage detailed analytics to understand prompt performance, user engagement, and areas for improvement, informed by concrete data. Invite team members to collaborate in a shared environment, where everyone can contribute, review, and refine prompts together. Control access and permissions within your team, ensuring members can work effectively.

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Platforms Supported

Windows
Mac
Linux
Cloud
On-Premises
iPhone
iPad
Android
Chromebook

Audience

Product teams, software engineers, prompt engineers, AI developers, ML researchers, startup founders, and technical writers working on AI-powered features or language model integrations.

Audience

Prompt engineers and teams needing a solution to manage and test prompts in a unified space

Support

Phone Support
24/7 Live Support
Online

Support

Phone Support
24/7 Live Support
Online

API

Offers API

API

Offers API

Screenshots and Videos

No images available

Screenshots and Videos

Pricing

$60 one time
Free Version
Free Trial

Pricing

$4.99 per month
Free Version
Free Trial

Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

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Reviews/Ratings

Overall 0.0 / 5
ease 0.0 / 5
features 0.0 / 5
design 0.0 / 5
support 0.0 / 5

This software hasn't been reviewed yet. Be the first to provide a review:

Review this Software

Training

Documentation
Webinars
Live Online
In Person

Training

Documentation
Webinars
Live Online
In Person

Company Information

Langfa.st
Founded: 2025
United States
langfa.st/new

Company Information

PromptGround
www.promptground.io

Alternatives

Alternatives

Categories

Categories

Integrations

Node.js
Python

Integrations

Node.js
Python
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