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

Test, collaborate, version, and deploy prompts, from a single place, with PromptHub. Put an end to continuous copy and pasting and utilize variables to simplify prompt creation. Say goodbye to spreadsheets, and easily compare outputs side-by-side when tweaking prompts. Bring your datasets and test prompts at scale with batch testing. Make sure your prompts are consistent by testing with different models, variables, and parameters. Stream two conversations and test different models, system messages, or chat templates. Commit prompts, create branches, and collaborate seamlessly. We detect prompt changes, so you can focus on outputs. Review changes as a team, approve new versions, and keep everyone on the same page. Easily monitor requests, costs, and latencies. PromptHub makes it easy to test, version, and collaborate on prompts with your team. Our GitHub-style versioning and collaboration makes it easy to iterate your prompts with your team, and store them in one place.

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

Anyone looking for a tool to test their prompts to make sure they are consistent

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

No information available.
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

PromptHub
www.prompthub.us

Alternatives

Alternatives

Categories

Categories

Integrations

Axis LMS
Claude
GPT-3.5
Microsoft Azure
OpenAI
Zapier

Integrations

Axis LMS
Claude
GPT-3.5
Microsoft Azure
OpenAI
Zapier
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