Caffeine for Windows: Download, Safety Check and Switches

Caffeine for Windows is a free app from Zhorn Software that keeps your PC from sleeping, locking or starting the screen saver. It sits in the system tray as a coffee pot and sends an F15 key event, a key no keyboard has, every 59 seconds, so Windows thinks you are still at the keyboard. Download caffeine.zip from zhornsoftware.co.uk/caffeine, unzip it and run caffeine64.exe, the build for 64-bit Windows 10 and Windows 11. There is no installer. The current version is 1.98, from November 2024. Caffeine only works while the PC is on, and Slack Green keeps your Slack dot green from a server even with the PC off or the laptop closed, free for 7 days with no card.

We downloaded that zip on 3 October 2026 and checked both files inside it, so the sizes, hashes and scan results below are what you should get too.

What is inside caffeine.zip

The zip is 316,991 bytes, and the server lists it as last changed on 2 November 2024. It holds two programs and nothing else:

Both files report version 1.9.8.0, company "Zhorn Software" and the original name caffeine.exe. That last field is why scan sites list caffeine64.exe as caffeine.exe. Neither file carries a digital signature, so Windows SmartScreen can show "Windows protected your PC" with an unknown publisher the first time you run it. Click More info, then Run anyway, only if the file came from zhornsoftware.co.uk and its hash matches the table.

To check the hash yourself, open PowerShell in the folder and run:

Get-FileHash .\caffeine64.exe -Algorithm SHA256

The full value for caffeine64.exe is 98c0af01b4257e12679aaba3c148cdc95c9168f95ad17add25287a584d9070bf. A different value means you have a different build or a repackaged copy, which happens on download mirrors.

The program's import table matches what it claims to do. It calls SendInput for the key event, SetThreadExecutionState for the -stes and -allowss modes, GetSystemPowerStatus for -onac, WTSRegisterSessionNotification for -notwhenlocked and the Windows performance counter library for -cpu. It imports no networking library. The single flag on the 32-bit file comes from one engine out of 69, and the 64-bit file you should use has none.

The "Caffeine : Keep Your Computer Awake" app in the Microsoft Store is a different program. Its publisher is herbert Studio, not Zhorn Software, and Zhorn does not publish to the Store.

At best, Caffeine's F15 key press keeps Slack active while the PC is awake and unlocked. Once the PC locks or sleeps, or the lid closes, Slack sets you away. A server-side tool keeps your Slack dot green with no input, even while the laptop sleeps or the lid is closed.

How to set up Caffeine for Windows

• Unzip caffeine.zip into any folder you can write to. It runs without an install, so it works without admin rights, unless your company blocks unknown apps.
• Run caffeine64.exe. A coffee pot appears in the system tray. It may be hidden behind the ^ arrow until you drag it onto the taskbar.
• A full pot means Caffeine is keeping the PC awake. Double-click the pot to empty it and pause Caffeine, and again to turn it back on. Right-click it for timers such as Ten hours.
• To start it with Windows, put a shortcut to it in your Startup folder (press Win+R and type shell:startup).

The pot changes with the taskbar color. These are the icons stored in caffeine64.exe, taken out of the file, so you can tell at a glance whether it is on:

Caffeine switches worth using

Caffeine reads switches from its command line. Right-click your shortcut, choose Properties, and add them after the exe path in the Target box. Since version 1.95 the tooltip on the tray icon shows the switches Caffeine recognized, which is the quickest way to catch a typo. These are the most useful, from Zhorn's own list:

A work-hours shortcut looks like this. Use your own path to the exe:

"C:\Tools\caffeine\caffeine64.exe" -activeperiods:0900-1759 -onac -notwhenlocked

By default Caffeine sends only an F15 key-up event, not a full key press. Zhorn notes that this can still cause problems in PuTTY sessions, PowerPoint, Google Docs and Smartsheet. If you see odd behavior in those apps, try -useshift or -stes.

Caffeine alternatives for Windows

PowerToys Awake is part of Microsoft's free PowerToys and keeps the PC awake indefinitely, for a set time, or until a date and time, and sends no input. Microsoft's docs say it does not work while the lock screen is showing. More in does PowerToys Awake keep Slack or Teams active. Don't Sleep from SoftwareOK adds rules based on CPU load or network traffic; its options are in Don't Sleep for Windows. Mouse Jiggler from Arkane Systems fakes mouse input instead of a key; setup is in mouse jiggler for Windows.

With no app at all, set Settings, System, Power & battery, Screen and sleep to Never, or run two commands for when the PC is plugged in:

powercfg /change monitor-timeout-ac 0
powercfg /change standby-timeout-ac 0

Scripts that do the same job are in keep your computer awake with PowerShell.

Does Caffeine keep Teams and Slack active?

Teams usually stays Available. It sets you Away after about 5 minutes with no input anywhere on the PC, and the F15 event counts as input. The -stes and -allowss modes send no input, so with them Teams goes Away as usual. Timing details are in how long before Teams shows away, and every Caffeine app is tested against Teams in does Caffeine keep Teams active.

Slack probably stays active too, in the desktop app. The Slack desktop app reads the PC's idle time every 10 seconds (Slack desktop 4.52.178 code, checked 7 Oct 2026), and Caffeine's F15 key press resets that idle time the same way it does for Teams. We have not run this test on Windows. The -stes and -allowss modes send no input, so with them Slack goes away after 10 minutes. The Mac version of Caffeine sends no key at all, and in does Caffeine keep Slack active Slack went away at minute ten, and the Mac app itself is covered in Caffeine app for Mac. Options that do work for Slack on a PC are in keep Slack active on Windows.

On a work PC, keep in mind that SendInput events are marked by Windows as injected input, and monitoring tools can see a running caffeine64.exe process. See can a mouse jiggler be detected.

FAQ

Does Caffeine work on Windows 11?

Yes. Zhorn's changelog for version 1.98 says it added ES_CONTINUOUS to its SetThreadExecutionState call, the one -stes and -allowss use, to improve how it works under Windows 11. Use caffeine64.exe, because Windows 11 has no 32-bit edition.

How do I uninstall Caffeine for Windows?

Right-click the pot and choose Exit, then delete the folder you unzipped it into and the shortcut in shell:startup if you made one. Nothing was installed, so there is no entry in Apps to remove.

Is Caffeine for Windows the same app as Caffeine for Mac?

No. The Mac app with the same name was written separately, first by Lighthead Software and now by Dominic Rodemer, and it uses a macOS power assertion instead of a key event. Where to get it and what each setting does is in Caffeine app for Mac.