Download Flow Preview for Raspberry Pi

flow browser

Flow's goal is to render every website correctly - it already works well with most HTML UIs, but there is currently a long way left to go. This preview release is for those people who are curious where we are with a new browser engine.

We are aware of the major sites that don’t work in Flow, but we would welcome short test cases demonstrating bugs that may be the cause of sites failing to function. Details of how to report these are below. This is a technology preview, and certain security features are missing, so please be careful with passwords.

By downloading Flow you are agreeing to our terms and conditions, a copy of these are included in the download package.

See the recent changes.


From Chromium, select 'Show in folder', then right-click on the downloaded zip file and select 'Extract Here'. Pi models prior to the Pi 4 require the 'Fake KMS' GL Desktop driver to be installed to enable hardware acceleration in X11.

Flow can then be run by double-clicking, or from the terminal by changing directory to where the Flow executable is stored and typing:


On startup, Flow launches a welcome page. To launch with a different URL include the URL name:


Keyboard shortcuts

alt-leftBack Page (also ctrl-[)
alt-rightForward Page (also ctrl-])
ctrl-RReload Page
ctrl-shift-HHome page

Command line options

--geometry <width>x<height>Set the window size, in pixels.
--max-script-run-time <duration>Set the maximum time, in seconds, that a script can run before automatically terminated. The default is 25.
--verboseOutput verbose logging.
--versionOutput the user-agent string, including version numbering.

If you’d like to help us improve Flow

If you’d like to help us improve Flow, we’d appreciate knowing about sites that fail because of missing or buggy JavaScript support. We’re not quite ready to start receiving reports for rendering issues just yet, these are mostly down to missing features, so as we add them you’ll see those issues steadily disappear over time.

We’d like to know about issues that are easily reproducible. As it takes a long time to analyse what a website’s doing, we’ll give highest priority to bugs that are reported with a simple test case that reproduces the issue.

To let us know about a bug please email us at

Making your Raspberry Pi animate faster

There are a few ways to boost the graphics performance of Flow running on the Raspberry Pi.

Disabling the CPU governor

The Raspberry Pi dynamically reduces the CPU clock speed when it’s determined the CPU is not under load. Unfortunately, the algorithm it uses does not appear to consider GPU load. When animating, Flow makes heavy use of the GPU but little use of the CPU, so the clock speed is reduced. This is mostly apparent during benchmarks.

To disable this until the next reboot, type:

echo performance | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Solid 60fps at 1080p

The Pi400 does not seem to be able to get 60fps at 1920x1080 resolution, or solid 30fps at 4k. This can affect benchmarks that aim to achieve a consistent 30fps.

Disabling the composition manager can help overcome this.

sudo raspi-config

Select ‘Advanced Options’, then ‘Compositor’, then select ‘No’.

30Hz limits

Many benchmarks, including MotionMark, work by changing the complexity up and down to a point where the framerate settles at 30fps. If the monitor you’re connected to is only displaying 30Hz these demos will not work since they can never go above 30fps.

This is also the case for 4k since the Pi only supports 4k@30fps by default.

Issues with audio and video on the Raspberry Pi

Each subsequent OS release of Raspberry Pi OS improves the operating system's support for audio and video, which Flow then benefits from. We find that, prior to Bullseye, the default audio driver is incorrectly specified leading to no sound. Earlier buster versions can cause the whole computer to freeze.

Having said that, most issues with video are due to the lack of Media Source Extensions in Flow. We are addressing this.

Links on the welcome page

Popular Websites

The Guardian
Wikipedia (English)
The Register
Scientific American


UI Layers
Motion Mark
Particle Acceleration