Introduction

Civitai Apps let you build a small web app that renders inside civitai.com — a self-contained UI, embedded in a sandboxed iframe, that the host authenticates, sizes, and connects to Civitai capabilities (the viewer, Buzz, generation) on your behalf. You ship a static single-page app; you don't run a backend, manage OAuth, or operate any infrastructure.

Closed beta — access is limited

Civitai Apps is currently in closed beta and is not yet generally available. The platform is mod-gated: building and publishing an app is limited to approved builders, and it is not openly self-serve today. If you'd like to build an app, reach out to the Civitai team to request access. (There is not yet a public self-signup flow.)

What is a Civitai App?

The runtime unit is a block: a static web app, served from its own platform-owned subdomain (https://<slug>.civit.ai/), declared by a small block.manifest.json. The host page (civitai.com) draws a trust frame around your iframe, hands it a short-lived, scoped token plus the current page context over postMessage, and brokers anything privileged — so your app never holds a long-lived credential and never talks to Civitai's privileged APIs directly.

Naming: the product is Civitai Apps; the code, manifest, scopes, and messages still use the block / app_block vocabulary. You'll see both in these docs — an "app" is what a user installs; a "block" is the hosted iframe unit it ships.

The result is a tight contract:

• You own the UI — a normal Vite + React (or any framework) SPA.
• The platform owns hosting, the subdomain, the runtime image, token minting, and the review/deploy pipeline.
• The host mediates every privileged action (generation, Buzz, storage, navigation) so policy is enforced on Civitai's side of the iframe boundary.

Page apps and slot apps

A block can render in two places:

• Page apps — a full-page app opened from the Apps area on civitai.com (/apps/run/<slug>), rendered full-bleed under Civitai's chrome. These docs target page apps.
• Slot apps — a block embedded in a named region of another page (for example, a model-page sidebar). Slot apps exist in the platform but are deferred / disabled for third-party builders right now. Build a page app.

What you'll need

• Node ≥ 20 and pnpm.
• A Civitai account, and closed-beta builder access (see the banner above).
• Basic familiarity with React — the starter and SDK are React-first.

You do not need Docker, a domain, a git host, or an OAuth client — the platform provisions all of that when your app is approved.

Where to start

• Concepts — the mental model: block, install, slot, the iframe trust frame, and how the host and your app talk to each other.
• Quickstart — go from nothing to a block running in the local harness using the @civitai/blocks-cli scaffold.

Once you understand the shape, the @civitai/blocks-react and @civitai/app-sdk packages carry the full hook and contract surface.