A Windows screen saver that plays real 4K video — Apple TV's Aerial footage, plus roughly 1,500 more 4K clips from the Internet Archive, NASA, and a few vendor "ambient TV" feeds — with smooth clip-to-clip transitions, a size-limited local cache so repeat clips play from disk instead of re-streaming, and a keyboard shortcut to trigger it the moment you're about to step away from your desk.

This is an unofficial, hobby project. It is not made by, affiliated with, or endorsed by Apple, NASA, the Internet Archive, or anyone else whose public video it streams. See docs/THIRD-PARTY-NOTICES.md for exactly what it bundles and streams, and under what licenses — some of the Internet Archive clips are non-commercial-only (CC BY-NC-ND), which this document says plainly rather than glossing over.

Features

• True 4K, not upscaled 1080p — HEVC/H.265 Main10, hardware-decoded on any GPU from the last several years.
• ~1,500 browsable clips from Apple's Aerials CDN, the Internet Archive, NASA, and a few vendor ambient-TV feeds, searchable and filterable by tag in a Wallpaper-Engine-style browser.
• Gapless transitions between clips, with a bounded, resumable local cache so repeat clips play instantly from disk instead of re-streaming.
• One-press walk-away hotkey (Ctrl+Alt+S) that triggers the real Windows screen saver — including your lock-on-resume setting, not just a video playing on top.
• Built-in auto-updates, checked from the clip browser and installed with a verified download — no reinstalling by hand for every release.

What you need

• Windows 10 or 11, 64-bit. (32-bit Windows isn't supported.)
• Free disk space for the video cache. You choose the size (default suggestion: a few GB up to however much you're comfortable with; it's a slider from 1–500 GB in the clip browser's Cache settings). Nothing is downloaded until the screen saver actually plays it, so a fresh install uses almost no disk space.
• An internet connection, at least for the first run and whenever you want new clips. A small bundled fallback lets the original Apple clip set work even if Apple's servers are briefly unreachable, but everything else streams on demand.
• A GPU capable of hardware HEVC/H.265 decode — true of basically any graphics card or integrated GPU from the last several years. Video will still play without one (the app falls back to decoding in software), just using more CPU and battery than it should. If playback looks choppy on an older machine, installing the free "HEVC Video Extensions from Device Manufacturer" app from the Microsoft Store is worth trying, though Win4KSS does its own decoding and doesn't strictly depend on it.

Nothing else to install by hand. If the PC lacks the .NET 10 Desktop Runtime or the Microsoft Edge WebView2 Runtime, the installer downloads them from Microsoft and installs them for you. ffmpeg, which makes the clip browser's previews, ships with Win4KSS.

Installing

1. Download Win4KSS-Setup-<version>.exe from the latest release.
2. Double-click it. Windows will very likely show a blue "Windows protected your PC" screen first — that's SmartScreen objecting to an installer with no paid code-signing certificate, not a sign anything is wrong. Click More info, then Run anyway. (More detail in docs/TROUBLESHOOTING.md if you want it.)
3. On the Tasks page, leave "Make Win4KSS available in Windows' Screen Saver Settings" ticked unless you have a reason not to — it's what makes Win4KSS show up as a normal choice in Windows' own screen saver picker later. The second option, setting it as your active screen saver right now with a 10-minute idle timeout, is unticked by default; tick it if you want that set up immediately instead of doing it yourself afterward.
4. Windows asks "Do you want to allow this app to make changes" once, to add Win4KSS to that screen saver list (and, on a PC that lacks it, to install the .NET runtime). Win4KSS itself installs into your user folder and needs no admin rights; if you say no, everything works except the entry in Windows' list.
5. Finish. You'll end up with:
   • The Ctrl+Alt+S hotkey, ready straight away and after every sign-in.
   • A "Start Screen Saver" shortcut on your Desktop and in the Start Menu (optional; you can remove them and the hotkey keeps working).
   • A "Win4KSS" entry in the Start Menu that opens the clip browser.

Using it

The walk-away hotkey: Ctrl+Alt+S

Press it any time you're stepping away and want the screen saver to kick in immediately, rather than waiting out your idle timeout. If Windows is set up to require your password (or show the lock screen) when the screen saver ends — Settings → Personalization → Lock screen → Screen saver settings → "On resume, display logon screen" — this hotkey honours that: the machine actually locks, not just shows a video. That's the entire point of it.

It works anywhere in Windows, whether or not the shortcuts exist, and you can change or turn it off in the clip browser (gear icon → Start now). A tiny background helper listens for it; it starts when you sign in and shows up as "Win4KSS" in Task Manager's startup apps.

The clip browser

Open it from the Start Menu ("Win4KSS") or by running the installed app with /c. This is where you pick what the screen saver actually plays:

• The toolbar across the top: search, a sort dropdown, small/medium/large card sizes, a "Select all filtered" button, a "Refresh catalogues" button (re-checks the Internet Archive, NASA, and the aerial manifest mirrors for new clips), a "Start now" button, and a gear icon for Settings.
• The sidebar on the left filters the grid by tag (source, category, resolution, and so on).
• The grid in the middle shows every clip as a card; hover one to see a short preview play.
• Clicking a card opens the detail pane on the right: a live preview, an "In rotation" switch (whether the screen saver will actually play this clip), a "Keep offline" switch (pins it so it's always cached and never evicted, even under disk pressure), its download/caching progress, and its captions, description, credit, and tags.
• Selecting several cards brings up a bulk action bar at the bottom to add/remove them from rotation or pin/unpin them all at once.
• The gear icon opens Settings, with five tabs:
  • Sources — turn Apple's aerials, your own local folders, and the harvested catalogues (Internet Archive, NASA, vendor feeds) on or off, and toggle "auto-add" per source so new clips a refresh finds join the rotation automatically.
  • Playback — video quality (4K SDR/HDR, 1080p variants).
  • Cache — the size budget slider, and a breakdown of how much is pinned ("kept offline") versus the normal rolling cache.
  • Start now — the hotkey recorder (click the box, then press the combination you want; it needs at least one of Ctrl/Alt/Shift plus a key, and takes effect at once), and the optional Desktop/Start Menu shortcut toggles.
  • About — version info, and an Updates section that checks for, downloads, and installs new releases. Updates install quietly — no installer pages and no Windows permission prompt — and the clip browser reopens on the new version.

Making it your actual idle-timeout screen saver

If you didn't tick the box during install, you can do it any time:

• Through Windows itself: Settings → Personalization → Lock screen → Screen saver settings, pick Win4KSS from the dropdown, and choose your own idle time and whether to require sign-in on resume. (This needs the System32 registration from step 4 above to show up in the dropdown at all.)
• Through the clip browser: gear icon → Start now tab has the same shortcut/hotkey controls the installer sets up, if you ever want to change them.

Uninstalling

Settings → Apps → Win4KSS → Uninstall. It asks separately whether to also delete the video cache, which can be tens of gigabytes — it defaults to keeping it, in case you reinstall later.

Something not working?

See docs/TROUBLESHOOTING.md — it covers the SmartScreen warning, the dropdown-visibility step, why you should never force-close a running screen saver from Task Manager, hotkey issues, and a few other common snags.

Licensing and credits

Win4KSS's own source is licensed under the GNU General Public License v3.0.

Win4KSS streams Apple's own Aerials CDN, the Internet Archive, NASA's video library, and a few vendor/community feeds — see docs/THIRD-PARTY-NOTICES.md for exactly what comes from where, under what license, and what that means for how you can use it (short version: personal viewing, not commercial use or redistribution of the video itself). It also bundles a GPL build of libmpv; that document explains what that obligates.

Code signing policy

See docs/SIGNING-POLICY.md for how releases are built and signed.