What is App Stack Builder?

App Stack Builder is a free AI-powered tool that helps founders and developers choose the right tech stack for their projects based on budget, app type, team size, and skill level.

What is the best tech stack for SaaS in 2026?

The best tech stack for SaaS in 2026 typically includes Next.js 16 for frontend, Supabase for database and auth, Vercel for hosting, Stripe for payments, and PostHog for analytics. App Stack Builder can generate a personalized recommendation based on your specific budget and requirements.

Is App Stack Builder free to use?

Yes, App Stack Builder is completely free to use. You can generate unlimited tech stack recommendations without any cost.

What types of apps can I build with the recommended stacks?

App Stack Builder supports various app types including SaaS applications, web apps, mobile apps, e-commerce stores, internal tools, and AI/ML products.

How much does a SaaS tech stack cost per month?

A modern SaaS tech stack can cost anywhere from $0-50/month for bootstrapped startups using free tiers, $100-300/month for growth-stage startups, to $500+/month for enterprise-ready infrastructure. App Stack Builder helps you find the best tools within your specific budget.

What is the best tech stack for solo founders?

For solo founders, we recommend Next.js + Vercel (free), Supabase (free tier), Supabase Auth (free), Stripe (pay as you go), and Plausible or PostHog for analytics. This stack can run your entire SaaS for under $50/month.

Can I export my tech stack recommendations?

Yes, you can export your tech stack recommendations as a PDF document or copy them to your clipboard. You can also share a link to your stack with others.

AI Evals & Agent TestingFree tier

Promptfoo: Pricing, Features & Alternatives

Promptfoo runs declarative test suites against your prompts, models and agents from the command line or CI, and compares outputs side by side across providers. Its red-teaming mode generates adversarial probes for jailbreaks, prompt injection, PII leaks and harmful output, which is why security teams use it. The core is MIT-licensed (about 26K GitHub stars) and the Community edition is free forever, including 10K red-team probes a month and self-hosting. Enterprise and On-Premise add team sharing, continuous monitoring, SSO and a compliance dashboard at custom prices. OpenAI agreed to acquire Promptfoo in March 2026 and said the open-source project would continue.

Promptfoo Pricing Plans (2026)

Plan	Price	Highlights
CommunityPopular	$0 (open source, MIT)	All eval features and providers · Red teaming: 10K probes / month · Self-hosting
Enterprise	Custom	Team sharing · Continuous monitoring · SSO and permissions
On-Premise	Custom	Your own infrastructure · Complete data isolation · Dedicated deployment engineer

Pricing summary: Free · paid plans by quote. Always confirm current pricing on the official site.

Key Promptfoo Features

All eval features and providers
Red teaming: 10K probes / month
Self-hosting
CI integration

Pros

+Free and open source (MIT)
+Best-known red-teaming suite for LLM apps
+Config-file tests that run in CI

Cons

−Owned by OpenAI since 2026, so roadmap may follow OpenAI's platform
−YAML configs get long for complex agents
−Team features are Enterprise-only

Best Promptfoo Alternatives

Compare all

DeepEval

Free · paid from $200/mo

Ragas

Free

Coval

From $100/mo

Promptfoo Compared

Promptfoo vs DeepEval Promptfoo vs Ragas Promptfoo vs Coval

Promptfoo FAQ

What is Promptfoo used for?⌄

Promptfoo is a ai evals & agent testing tool. Open-source CLI for testing prompts, agents and RAG apps, with built-in red teaming for jailbreaks, prompt injection and data leaks.

Is Promptfoo free?⌄

Yes — Promptfoo has a free tier you can start with, and paid plans for more usage and features.

How much does Promptfoo cost?⌄

Promptfoo is free to use, with usage-based pricing on some features.

What are the best Promptfoo alternatives?⌄

Popular Promptfoo alternatives include DeepEval, Ragas, Coval. Compare pricing and features on our Promptfoo alternatives page.