The prompt is the product.
Test it like one.

Iterate on any prompt against any model - without spinning up your entire stack. No setup, no pipeline, no 10-minute wait.

OpenAIAnthropicGoogle Gemini

Two ways to test a prompt

One costs you hours. The other, seconds.

The old way
bash — my-ai-project
Scroll down to watch...
With PromptFast

↑ click to run the demo

Response will stream here...

Features

Everything you need to test, refine, and perfect your AI prompts in one intuitive interface.

Instant Testing

Test your prompts instantly without any setup. Get immediate feedback and iterate in real-time.

Write a product description for...
Run
Response 1.2s

Multiple AI Providers

Access 13+ models across OpenAI, Anthropic, and Google.

OpenAI
GPT-4oGPT-5
Anthropic
SonnetOpus
Google
Gemini ProFlash

Dynamic Variables

Use dynamic variables to test different scenarios without rewriting your prompt.

Write a {{tone}} email to {{recipient}} about {{topic}}
tone=professional
recipient=hiring manager
topic=job application

System Prompts

Configure custom system prompts to define AI behavior and personality.

system_prompt
You are a senior software engineer with 10+ years of experience. Always respond with clean, production-ready code. Follow best practices and include brief explanations.

Token & Cost Tracking

Monitor tokens with detailed cost breakdowns.

Input
1,247
Output
583
Total: $0.0024

File Upload Context

Upload PDF, Word, Excel, CSV, and JSON files as context.

.pdf
.docx
.csv
.xlsx
.json
.txt
Drop files here

Real-time Streaming

Watch responses generate live as they stream in.

The quick brown fox
jumps over the lazy
dog. This sentence is
being streamed in
real-time

Prompt History

Browse, reload, and manage your past prompts with full token tracking.

Write a product description...GPT-4o1,830t2m ago
Summarize this article about...Sonnet2,145t15m ago
Generate test cases for the...Gemini956t1h ago

Model Comparison

Compare responses side-by-side across different models simultaneously.

GPT-4o
Claude Sonnet

Pricing

Simple, transparent pricing. Pick the plan that works for you.

Yearly Plan

Most Popular

Full access, billed annually.

€45/yr~€3.75/mo
  • Unlimited prompt testing
  • All AI providers
  • Prompt history & analytics

Monthly Plan

Full access, billed monthly.

€5/mo
  • Unlimited prompt testing
  • All AI providers
  • Prompt history & analytics

Lifetime

Pay once, use forever.

€95/one-time
  • Unlimited prompt testing
  • Unlimited access
  • Priority support

Public Roadmap

Here's what we're building next — in order of priority. Have a request? Use the feedback box below.

Custom Tools Integration

Add and configure custom tools directly from the interface. Test function calling and tool use patterns with your own API definitions.

Response Analytics

Get detailed metrics on token usage, response times, and cost estimates. Optimize your prompts for both quality and efficiency.

Batch Testing

Test multiple prompt variations simultaneously. Run A/B tests and compare responses across different configurations at scale.

Collaborative Workspaces

Share your prompts with team members. Collaborate on prompt engineering and maintain a shared library of tested configurations.

Export to Code

Generate production-ready code snippets from your tested prompts. Export in Python, JavaScript, or as API calls.

Prompt Improver

Enter your prompt, test it, and let AI craft a better version for you.

Share Your Thoughts

Have ideas for new features? Found a bug? We'd love to hear from you.