LangFast

LangFast

Langfa.st
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+

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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

Get everything you need to start customizing LLMs and prompts immediately, no PhD required. Starter Kits with model, prompt, and dataset suggestions matched to your use case allow you to begin testing, evaluating, and refining model outputs right away. Experiment with multiple models (proprietary and open source), prompts, and techniques simultaneously to speed up the iteration process. Automated testing and evaluation and AI-powered prompt and refinement suggestions enable you to run many experiments at once to quickly achieve high-quality results. Verta’s easy-to-use platform empowers builders of all tech levels to achieve high-quality model outputs quickly. Using a human-in-the-loop approach to evaluation, Verta prioritizes human feedback at key points in the iteration cycle to capture expertise and develop IP to differentiate your GenAI products. Easily keep track of your best-performing options from Verta’s Leaderboard.

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Not Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

Platforms Supported

Windows Not Supported
Mac Not Supported
Linux Not Supported
Cloud Supported
On-Premises Not Supported
iPhone Not Supported
iPad Not Supported
Android Not Supported
Chromebook Not Supported

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

Data science teams in search of an AI solution to accelerate the development and deployment of applications and ML models

Support

Phone Support Not Supported
24/7 Live Support Not Supported
Online Not Supported

Support

Phone Support Not Supported
24/7 Live Support Supported
Online Supported

API

Offers API Not Supported

API

Offers API Supported

Screenshots and Videos

No images available

Screenshots and Videos

Pricing

$60 one time
Free Version Not Supported
Free Trial Supported

Pricing

No information available.
Free Version Not Supported
Free Trial Supported

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

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 Not Supported
Webinars Not Supported
Live Online Not Supported
In Person Not Supported

Training

Documentation Supported
Webinars Supported
Live Online Not Supported
In Person Not Supported

Company Information

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

Company Information

Verta
United States
www.verta.ai/

Alternatives

Alternatives

Categories

Prompt Engineering Supported

Categories

Integrations

Codestral Not Supported
Codestral Mamba Not Supported
Falcon Not Supported
Llama 2 Not Supported
Mathstral Not Supported
Ministral 3B Not Supported
Ministral 8B Not Supported
Mistral 7B Not Supported
Mistral AI Not Supported
Mistral Large Not Supported
Mistral NeMo Not Supported
Mistral Small Not Supported
Mixtral 8x22B Not Supported
Mixtral 8x7B Not Supported
Pixtral Large Not Supported

Integrations

Codestral Supported
Codestral Mamba Supported
Falcon Supported
Llama 2 Supported
Mathstral Supported
Ministral 3B Supported
Ministral 8B Supported
Mistral 7B Supported
Mistral AI Supported
Mistral Large Supported
Mistral NeMo Supported
Mistral Small Supported
Mixtral 8x22B Supported
Mixtral 8x7B Supported
Pixtral Large Supported
Claim LangFast and update features and information
Claim LangFast and update features and information
Claim Verta and update features and information
Claim Verta and update features and information