Astro Dimmer gently turns your monitors down at sunset and brings them back up at sunrise, every day, without you lifting a finger.
Free and open source · Windows 10 and 11 · No administrator needed
Zip, to run without installing · Other releases, including ARM-based PCs
How it works
Tell Astro Dimmer where you are and it works out when the sun rises and sets, every day of the year. Your screens follow along on their own.
Screens ease back up as the day begins.
Full, crisp brightness for a well-lit room.
A slow, gentle fade as the light outside goes.
Softer screens that are kinder to tired eyes.
Right where you need it
Click the small icon at the bottom of your screen and a panel slides up with a slider for each monitor. It looks and feels like it came with Windows.
Follows the sun
Drop a pin on the map, or let Windows find you, and Astro Dimmer does the astronomy. Sunrise in June is not sunrise in December, and it keeps up with both.
Your timing
Like your screens bright a little longer in the evening? Shift sunset by up to three hours. Prefer a slow dusk to a sudden switch? Let the change fade in over an hour.
Every monitor its own way
Your big main monitor and the one off to the side don't need to match. Pick a daytime and a night-time level for each, and Astro Dimmer moves them between the two.
The small things
No cost, no account, no sign-up. Your location is only used on your own computer.
Sits quietly in the corner of your taskbar and uses next to nothing while it waits.
Available in 19 languages, from Danish to Japanese, and follows your Windows setting.
A normal installer that needs no administrator password.
Connect or unplug a monitor and it notices by itself, no restart needed.
Its icon changes between sun and moon, so you know which mode you're in at a glance.
Questions
Astro Dimmer works with separate monitors plugged into your computer, which covers most monitors sold in recent years, and with the built-in screen of a laptop. If a monitor doesn't show up, look in its own on-screen menu for a setting called DDC/CI and switch it on. A laptop screen follows the schedule for brightness only; contrast is for monitors that offer it.
No, and the two get along fine. Night Light makes the colours warmer. Astro Dimmer turns the actual brightness of the monitor down, the same as pressing the buttons on the screen itself. Many people use both.
Just drag the slider. Astro Dimmer respects your choice and leaves that screen alone until the next sunrise or sunset, then carries on as normal.
Nowhere. It is stored on your computer and only used to work out sunrise and sunset. If you press Auto position detection, Astro Dimmer asks Windows first, and only uses an online lookup if Windows can't say. More about privacy
Windows 11, and Windows 10 from the October 2018 update onwards, on both regular PCs and ARM-based ones.
Yes. Each release also comes as a zip: extract it anywhere, open the AstroDimmer folder and run AstroDimmer.exe. Extract the whole zip first, as it won't run from inside it. Your settings are still kept in your Windows user profile, not in the folder. To update, quit Astro Dimmer from its tray icon and replace the folder with the new one.
Like any other app: open Settings › Apps › Installed apps, find Astro Dimmer and choose Uninstall. Running it from the zip? Turn off Start with Windows in its Settings, quit it, then delete the folder.
The fine print
Astro Dimmer does not collect any data. It has no account, no analytics and no tracking, and it never sends anything to its developer. Your location and settings are stored only on your computer, in your Windows user profile.
This program will not transfer any information to other networked systems unless specifically requested by the user or the person installing or operating it. To find where you are, Astro Dimmer asks Windows location services for your approximate position: when you press Auto position detection, and once when Settings first opens with no location saved. Windows decides whether to answer, following your location settings. Only if you pressed the button and Windows can't say does Astro Dimmer ask the online service ipapi.co to estimate your location from your internet address. Nothing else is sent. Placing the pin on the map yourself needs no location lookup at all.
Download Astro Dimmer, pick your spot on the map, and enjoy calmer evenings from today.