Application Integration

Use this page as the integration contract for humans and coding agents adding the browser package supervision from the supervision-js repository to another web application.

Installation

The browser package is published as supervision. There is no CDN, UMD, or <script> build. Install the current browser release with npm:

npm install supervision
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The published package includes the internal supervision-js-core dependency. Consumers must not install supervision-js-core separately.

Supported Consumer

Use:

• a browser application;
• Node.js 20.19 or newer for install and build tooling;
• an npm-compatible package manager;
• an ESM-aware bundler such as Vite, webpack, Parcel, or esbuild.

The default render-preparation worker is embedded in the package and runs from a Blob URL. Consumers do not need to copy a worker file or configure a bundler-specific worker loader.

The renderer requires browser APIs. In an SSR application, create sessions only on the client after the container element exists. The package can be imported by build tooling, but createMediaSession() must not run during server rendering.

Do not import Pixi, Mediabunny, worker protocols, or internal core modules. Import the supported JavaScript entrypoints:

import { createMediaSession } from "supervision";
import { createMaskBrushEditor } from "supervision/editing";
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Minimal Browser Integration

Give the viewer a non-zero size. The renderer appends and resizes its own canvas inside this element:

<div id="viewer"></div>
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#viewer {
  width: 100%;
  aspect-ratio: 16 / 9;
  background: #020617;
  overflow: hidden;
}

#viewer canvas {
  display: block;
}
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Create one session for one media item:

import {
  BaseBoxStyle,
  BaseLabelStyle,
  createMediaSession,
  type MediaSession,
} from "supervision";

const container = document.querySelector<HTMLElement>("#viewer");

if (!container) {
  throw new Error("Missing #viewer container.");
}

let session: MediaSession | null = await createMediaSession({
  container,
  media: "/media/example.mp4",
  presentation: {
    boxStyle: new BaseBoxStyle(),
    labelStyle: new BaseLabelStyle({ includeConfidence: true }),
  },
  renderer: {
    autoPlay: false,
    loop: true,
  },
});

const unsubscribe = session.subscribe((state) => {
  console.log(state.status, state.playbackBlocked, state.errorMessage);
});

await session.play();

// Run when the view unmounts or another media item replaces this one.
unsubscribe();
session.destroy();
session = null;
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media accepts a URL string, File/Blob, or an advanced MediaRendererSource.

Add Static Detections

Pass semantic detection frames at session creation:

import type { DetectionFrame } from "supervision";

const frames: DetectionFrame[] = [
  {
    frameIndex: 0,
    mediaTime: 0,
    endTime: 1 / 30,
    detections: [
      {
        id: "person-1",
        className: "person",
        confidence: 0.92,
        rect: {
          x: 240,
          y: 290,
          width: 240,
          height: 420,
        },
      },
    ],
  },
];

const session = await createMediaSession({
  container,
  media: "/media/example.mp4",
  detections: { frames },
});
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Geometry uses media pixels, not CSS pixels:

• rect.x and rect.y are the rectangle center;
• width and height must be positive;
• polygon, polyline, and keypoint points use { x, y } media coordinates;
• mediaTime and endTime are seconds;
• confidence is between 0 and 1;
• styles belong in presentation, not in detection records.

Append Detections From Inference

The host application owns model calls. The session can own appendable detection storage and rendering:

const session = await createMediaSession({
  container,
  media: uploadedFile,
  normalize: { stream: true },
  detections: {
    appendable: {
      datasetId: "upload-123",
    },
  },
});

for await (const batch of inferenceResults) {
  await session.appendDetectionFrames(batch);
}
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Use a stable, app-owned datasetId. Do not pass rendered canvases, Pixi objects, or prepared mask textures. Append DetectionFrame values.

Host And Library Ownership

The host application owns:

• UI components and framework state;
• authentication, uploads, and inference requests;
• persistence and business workflow;
• converting model output into DetectionFrame values;
• calling destroy() when a viewer is removed.

The supervision package owns:

• media probing, optional normalization, and playback;
• the renderer canvas and Pixi scene;
• detection buffering and frame selection;
• prepared mask artifacts and browser workers;
• presentation, picking, and renderer state;
• resources scoped to the session.

Choose The Right Detection Input

Use exactly one of these for a normal single-source session:

Input	Use when
detections.frames	All detections are already available.
detections.source	The app loads time ranges through a custom source.
detections.appendable	Results arrive after the session starts.
detections.sources	Separate app-owned streams need independent writes, ordering, or styles.

Do not combine detections.sources with the three single-source inputs.

Lifecycle Rules

• Create one session per media item and viewer element.
• Destroy the old session before creating a replacement in the same element.
• Retain and call the unsubscribe function returned by subscribe().
• Treat a destroyed session as terminal.
• Keep API keys and inference logic outside the library.
• In React or another component framework, create the session after mount and destroy it in the effect cleanup.

See React Integration for a complete component pattern.

Strict CSP Worker Hosting

The zero-configuration default requires worker-src blob:. If the application's Content Security Policy disallows Blob workers, copy the standalone script exported at supervision/render-preparation-worker into the application's public assets during its build, then provide a worker factory:

import { RenderPreparationMode, createMediaSession } from "supervision";

const session = await createMediaSession({
  container,
  media,
  renderer: {
    renderPreparation: {
      mode: RenderPreparationMode.Worker,
      workerFactory: {
        createWorker: () =>
          new Worker("/assets/supervision-mask-preparation.worker.js", {
            name: "supervision-render-preparation",
          }),
      },
    },
  },
});
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Serve that asset from an origin allowed by worker-src. The standalone file is self-contained, so it does not need adjacent JavaScript chunks. Its message protocol is internal; applications should only use it through workerFactory.

Verification Checklist

Before considering an integration complete:

1. npm ci succeeds in a fresh checkout of the consuming application.
2. Render-preparation diagnostics report worker / ready in the production build when workers are enabled.
3. The viewer element has a non-zero width and height.
4. Media renders from the same URL/File type used in production.
5. At least one known detection appears at the expected media coordinate.
6. Session state and errors are surfaced to the host UI.
7. Navigating away destroys the session without leaving a canvas or active playback behind.

Common Integration Mistakes

• Installing supervision-web instead of supervision.
• Installing supervision-js-core separately.
• Running createMediaSession() during SSR.
• Mounting into a zero-height container.
• Treating rectangle x and y as top-left coordinates.
• Storing colors or canvas objects in detections instead of using styles.
• Creating a second session without destroying the first.
• Importing internal worker protocols, Pixi, Mediabunny, or prepared-artifact modules.