Metal Acceleration in Bromure Web

The standalone Bromure web browser can accelerate its Linux browser VMs with the Mac's GPU through Metal. This page describes that app's settings; the Agentic Coding embedded browser has its own Browser settings.

Metal accelerates browser graphics, including compositing and supported WebGL workloads. Each accelerated VM has its own renderer worker, so several browser windows can use acceleration at once. The guest remains a Linux VM, and the mouse cursor is presented by macOS using the guest's cursor images.

Requirements and defaults

Metal requires Apple Silicon, macOS 27 or later, and a compatible browser image. Both the app-wide and profile choices default to enabled, including profiles saved before the profile option existed. A previously saved app-wide off choice remains off.

Bromure 5.0.1 uses browser image 501, which includes fixes for H.264 video transfer overhead and a graphics fence leak that could restart the browser's GPU process during extended playback. Update the browser image as well as the app to receive those guest-side fixes.

On macOS 26 and earlier, the Metal controls are greyed out. A browser image without the required graphics capability information uses the legacy graphics path. Updating an image does not force older applications or unsupported hosts to use Metal.

Enable or disable Metal

In the standalone Bromure app:

  1. Open Settings → Hardware and enable Use Metal Renderer. This is the app-wide master setting.
  2. Open the profile editor, select Performance, and enable GPU Acceleration and Metal Renderer for the profile.
  3. Open a new browser window for that profile. Renderer changes apply to new windows; an already running VM keeps its renderer.

The profile's Metal Renderer switch is also greyed out while GPU Acceleration is off. Turning Metal off for one profile selects the legacy graphics path for its new windows while other profiles can continue using Metal. WebGL remains a separate profile option: enable it when a site requires 3D graphics.

Check which renderer is active

An accelerated window shows the Metal logo in its browser chrome. Its GPU menu reports Metal as the active renderer. A window using the legacy path has no Metal badge. Enabling the setting expresses a preference; the active-window indicator confirms whether the required host and image support were available when that VM started.

Video playback and limits

The Metal path supports hardware decoding of H.264 through the Mac's VideoToolbox framework. Codec selection still matters: a site serving AV1 can use software decoding. Graphics acceleration does not mean every video format is decoded in hardware.

This graphics device does not expose general GPU compute to Linux. It does not make CUDA, Metal compute, or local LLM inference available inside a browser VM. Agentic Coding's on-device models run separately on the Mac.

If Metal does not appear

Check the macOS version, both Metal settings, and GPU Acceleration in the profile. Install the compatible browser image supplied with the GPU-capable build, then open a fresh window. An older window will not change renderer when you toggle a setting.

If a site has a graphics or video problem, turn Metal Renderer off for that profile and compare in a new window. Include the macOS version, app build, image version, page URL, and whether the Metal logo appeared when reporting the problem.