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.

Agent Sandboxes & Code Execution

The 2 Best Modal Alternatives in 2026

Name: App Stack Builder
Availability: InStock

Looking for an alternative to Modal? Below we compare the best agent sandboxes & code execution alternatives by pricing, free tiers, and what each is best for — so you can pick the right fit for your budget and stack.

Why look for a Modal alternative?

Modal is a solid agent sandboxes & code execution choice, but it isn't the right fit for everyone. The most common reasons teams evaluate alternatives:

−Python-first; other languages are second-class
−CPU sandbox rates are higher than dedicated sandbox vendors
−Team plan is a $250 step up

Modal vs Alternatives — Quick Comparison

Tool	Pricing	Rating	Best for
ModalYou searched	Free · paid from $250/mo	4.7	Agent Sandboxes & Code Execution — sandbox, serverless
1.E2B	Free · paid from $150/mo	4.6	Agent Sandboxes & Code Execution — sandbox, agents
2.Vercel Sandbox	Free · then usage-based	4.5	Agent Sandboxes & Code Execution — sandbox, firecracker

Top Modal Alternatives, Explained

1. E2B

Free tier4.6· Free · paid from $150/mo

E2B is the sandbox layer many agent products and code-interpreter features call when a model writes code that has to actually run. Each sandbox is an isolated microVM that starts in well under a second, with SDKs for Python and JavaScript and filesystem, process and network access. Compute is billed per second on every plan ($0.000014 per vCPU-second, $0.0000045 per GiB-second). Plans change the limits: Hobby is free with $100 of one-time credit, 1-hour sessions and 20 concurrent sandboxes. Pro is $150/month for 24-hour sessions and 100 concurrent sandboxes, with add-ons up to 1,100. Enterprise starts at $3,000/month and adds bring-your-own-cloud.

Purpose-built for agents, with SDKs designed around tool calls
Fast microVM startup with real isolation
Open-source core

E2B pricing & review Modal vs E2B

2. Vercel Sandbox

Free tier4.5· Free · then usage-based

Vercel Sandbox runs each session in an isolated Firecracker microVM, in 19 regions, with up to 8 vCPUs and 24-hour sessions on Pro. Its pricing suits agents well. Active CPU is billed only while code is actually executing ($0.128/hour); time spent waiting on an LLM call does not count. Memory is billed as provisioned ($0.0212/GB-hour), and downloads such as npm installs are free. Hobby includes 5 CPU-hours, 420 GB-hours and 5,000 creations a month, with 45-minute sessions and 10 concurrent sandboxes. On Pro, usage draws down the plan's $20 monthly credit first, and concurrency rises to 10,000.

Active-CPU billing: idle time waiting on the model is free
Firecracker isolation with snapshots and persistent drives
Natural fit if the app already runs on Vercel

Vercel Sandbox pricing & review Modal vs Vercel Sandbox

Frequently Asked Questions

What are the best alternatives to Modal in 2026?⌄

The best Modal alternatives in 2026 are E2B, Vercel Sandbox. Each is a agent sandboxes & code execution option you can compare on pricing, free tiers, and features in the table above.

Is there a free alternative to Modal?⌄

Yes — E2B, Vercel Sandbox offer free tiers, making them strong free Modal alternatives for bootstrapped startups.

Why look for a Modal alternative?⌄

A common reason teams switch is python-first; other languages are second-class. Beyond that, people compare agent sandboxes & code execution tools on pricing, specific feature gaps, ease of use, and whether an open-source or free-tier option exists — so they can pick the best fit for their stack and budget.

What is the cheapest Modal alternative?⌄

E2B is among the most affordable Modal alternatives — free · paid from $150/mo. Check the comparison table above for the full pricing breakdown.

Which Modal alternative is rated highest?⌄

E2B is the highest-rated Modal alternative in our catalog at 4.6 out of 5, making it a strong pick if you want a well-reviewed option.