Your idle screen, running the whole gallery

All of it lives in the Configure dialog, and all of it is stored in %LOCALAPPDATA%\bgHub\Screensaver\settings.json as plain text you can read.

Runtime cost

Which backgrounds may appear, by how expensive they are to render. Light and Medium are on by default; Heavy is the group that keeps a laptop fan running, so you opt into it.

Technique

Narrow the list to CSS, Canvas 2D, Three.js or GLSL. Useful on an old machine, where restricting it to CSS removes the GPU from the picture almost entirely.

Shuffle / only the selected background

Rotate through everything matching your filters, or pin the one background highlighted in the list.

Change every

Seconds each background is shown before the crossfade. Five minutes is the default; anything from 10 seconds to an hour is accepted.

Frame rate

The cap handed to the background itself, not a vsync setting. 30 fps looks identical to 60 on a screensaver and asks half as much of the machine.

Sharpness

A cap on device pixel ratio. On a 4K display, 1x renders a quarter of the pixels of 2x for a difference you cannot see from across a room.

Other screens

What non-primary displays do. Black is free, one still frame costs a couple of seconds of rendering and then nothing, and full animation multiplies the whole cost by the number of monitors.

Colours

Every background ships a dark and a light scheme. Dark is the default rather than following Windows, because an unattended machine at night is a room light.

Show the time and date

A large clock in the top-left corner of the primary display only.

Show each background's name

The title and technique in the bottom-left for a few seconds after each change. How you find out what you are looking at when you want to use it on a page.

Start after N minutes idle

Windows' own idle timeout, set from here so you do not have to open two dialogs. Shared with every other screensaver on the machine.

• Windows 10 (64-bit) or Windows 11. x64 only; there is no ARM64 build yet.
• Microsoft Edge WebView2 runtime. Preinstalled on Windows 11 and on any machine with a current Edge. The self test reports the version it found.
• .NET 9 Desktop Runtime, for this small download only:

winget install --id Microsoft.DotNet.DesktopRuntime.9 --source winget

To avoid that dependency, build the self-contained version instead. It carries its own runtime, so it needs nothing preinstalled, at the cost of being a considerably larger download.

git clone https://github.com/goldynlabs/project-bg
cd project-bg/frontend && npm install
cd ../screensaver/windows
.\build.ps1 -Flavor selfcontained -Zip

Either build passes the same verification script, screensaver/windows/verify.ps1, which drives every mode Windows can ask for and asserts what should have happened.

Nothing is installed system-wide, so there is nothing in Add or Remove Programs. Two folders and one registry value, and this clears all three:

# 1. stop being the screensaver
Start-Process "$env:LOCALAPPDATA\Programs\bgHub Screensaver\bgHubScreensaver.scr" `
  -ArgumentList "/uninstall" -Wait -NoNewWindow

# 2. delete the program and its settings
Remove-Item -Recurse -Force "$env:LOCALAPPDATA\Programs\bgHub Screensaver"
Remove-Item -Recurse -Force "$env:LOCALAPPDATA\bgHub"

Only want a different screensaver? Open Windows Screen Saver Settings and pick one. bgHub stops being used the moment you do; it leaves nothing running.

Worth knowing, because it explains both the strengths and the limits. Every background in the gallery already ships as a standalone HTML page sized to the viewport. The screensaver is that, unchanged: an export step copies one per pattern into a folder, replaces the Three.js import that pointed at a CDN with a bundled copy, and adds a small script ahead of each page that caps its frame rate and pixel density.

The Windows side is a small host that creates one borderless window per display and points a WebView2 at a single local page, which does the shuffling, the crossfade and the clock. The host answers the three command lines Windows gives a screensaver: /s to run fullscreen, /pto draw inside the settings page's preview box, and /c to open its options.

The consequence is that a change to how the screensaver behaves is a change to one HTML file, not a rebuild for each operating system, and that new backgrounds arrive by re-running the export rather than by writing any native code.

Not yet. The content side is done and portable, so a macOS build is a.saver bundle wrapping a WKWebView around the same page. The open question is whether WebGL runs inside the sandboxed process macOS hosts screensavers in; if it does not, the CSS and Canvas backgrounds still work, which is most of the catalogue. That needs a Mac to answer honestly, so it is not promised here.