Softwr

Web Development · head to head

FastAPI vs Preact

FastAPI logo

FastAPI

Web Development

A modern, fast, high-performance web framework for building APIs with Python

From
Free
Rated
-
Full reviewWebsite
Preact logo

Preact

Web Development

3kB alternative to React with the same modern API

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: FastAPI no built-in ORM, requires separate database libraries; Preact compatibility through preact/compat is good but not total, and some React libraries break in ways that are hard to diagnose
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which FastAPI and Preact actually diverge.

Attributes where FastAPI and Preact differ
AttributeFastAPIPreact
Pricing modelopen-sourceOpen source, no licence fee

Identical on both: starting price (Free), free tier (Yes), platforms (Web), user rating (Not yet rated), category (Web Development).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in FastAPI

Nothing recorded that Preact does not also cover.

Only in Preact

  • 3kB runtime
  • preact/compat
  • Same modern API
  • Fast rendering

What people use each for

The jobs each tool is most often brought in to do.

FastAPI

  • Building production-ready REST APIs with automatic validationnot Preact
  • Serving machine learning model predictions as REST servicesnot Preact
  • Building crisis management and orchestration platformsnot Preact
  • Enabling real-time APIs with WebSocket connectionsnot Preact
  • Rapid API development reducing boilerplate code significantlynot Preact

Preact

  • Embedded widgets that load inside someone else’s page and must stay smallnot FastAPI
  • Marketing and content sites where JavaScript payload affects Core Web Vitalsnot FastAPI
  • Applications targeting low-bandwidth or low-powered devicesnot FastAPI

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

FastAPI

  • No built-in ORM, requires separate database libraries
  • Python-only, cannot build with other languages
  • Async/await learning curve for developers new to async programming
  • Production deployment requires separate ASGI server configuration

Preact

  • Compatibility through preact/compat is good but not total, and some React libraries break in ways that are hard to diagnose
  • Behavioural differences from React exist in edge cases, particularly around event handling
  • A much smaller community, so unusual problems have fewer existing answers than React

Pricing, plan by plan

FastAPI

Free

No published plan breakdown. See the FastAPI review.

Preact

Free
  • PreactFree
    • Full library
    • Commercial use permitted
    • No usage limits

Which should you pick?

Choose FastAPI if

  • You want to start without paying.
FastAPI review

Choose Preact if

  • You need 3kb runtime.
  • You want to start without paying.
  • You also want preact/compat.
Preact review

Questions people ask

Is FastAPI or Preact better?
Neither clearly leads. FastAPI starts at Free and Preact at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, FastAPI or Preact?
FastAPI starts at Free and Preact at Free.
Does FastAPI or Preact run on more platforms?
Both run on Web, so platform support will not decide this one for you.
Can I use FastAPI for free?
Both have a free tier, so you can try either at no cost before committing.
What is FastAPI best used for?
FastAPI is most often used for building production-ready rest apis with automatic validation, serving machine learning model predictions as rest services, building crisis management and orchestration platforms, enabling real-time apis with websocket connections. Of those, building production-ready rest apis with automatic validation and serving machine learning model predictions as rest services are not what Preact is typically brought in for.
What can FastAPI do that Preact cannot?
Preact covers 3kB runtime, preact/compat, Same modern API, Fast rendering.

Answered from the vendors’ own pages

FastAPI: Is FastAPI free to use?

Yes. FastAPI is free and open-source under the MIT License. It costs nothing to download, use, or deploy in production. An optional paid service, FastAPI Cloud, offers one-command deployment for additional convenience, but the core framework is free.

Source
Preact: Is Preact free?

Yes, open source under the MIT licence.

FastAPI: Can I use FastAPI for commercial applications?

Yes. FastAPI's MIT License permits unrestricted commercial use, modification, and distribution. You can build and sell products powered by FastAPI without licensing fees or restrictions.

Source
Preact: Can I use React libraries with Preact?

Most, through the preact/compat layer. Compatibility is good but not complete, so libraries relying on React internals can break.

FastAPI: Does FastAPI include a database or ORM?

No. FastAPI does not include a built-in database or ORM. You must add separate libraries like SQLAlchemy for database access. This gives flexibility to choose the database solution best suited to your project.

Source
Preact: Why choose Preact over React?

Bundle size, almost always. If payload is not a binding constraint, React’s ecosystem is usually the better trade.

FastAPI: What Python versions does FastAPI support?

FastAPI supports Python 3.7 and later. Older Python versions are not compatible, so you must run at least Python 3.7 to use FastAPI.

Source
Share

Related pages

More on FastAPI

More on Preact

Keep looking

Other head to heads