# Rendering

> How Video renders an MP4 in your browser with WebCodecs: sizes, formats, the four-minute single pass, chapters and splitting, browsers, and what an AI can and cannot do.

Source: https://video.geenius.io/docs/rendering/

## In your browser

Rendering runs on your machine. Video draws each frame, encodes them to **H.264** with **WebCodecs**, mixes any sound into one **AAC** track and gives you an **MP4**. Nothing is uploaded and there is no queue. The preview and the render are the same drawing.

## Sizes

1080p, 720p, square and vertical.

## One pass is up to four minutes

A single render pass covers up to **240 seconds**. For a longer film, make it as **chapters** (a scene with a chapter marker starts a chapter), then **split**: one video per chapter, with the same look, titled "<title> - 1." and so on. Render each and join them afterwards.

## Browsers

Use a current Chrome, Edge or Safari with WebCodecs. The render needs an H.264 encoder in the browser.

## After the render

Download the file, or save it to the Geenius OS Media library together with its poster. If you edit the video after rendering, it is marked stale until you render again.

## Agents

Your AI cannot render. It drafts the video and gives you a link; you open it, watch the preview and press **Render**.

## Time and size

A render takes the time it takes on your device. A 204-second film took about 206 seconds on the machine we tried. Larger sizes and more layers take longer.