f.lux Alternatives in 2026: Free, Open Source, and Paid Picks Compared

Quick answer: which f.lux alternative to pick

Six f.lux alternatives are worth evaluating in 2026, each covering different needs. For free built-ins, Windows Night Light has shipped with Windows since the Windows 10 Creators Update in 2017, and macOS Night Shift does the same job on a Mac with no install either way. For open source, LightBulb is an MIT-licensed Windows app that shifts display gamma from cold blue in the afternoon to warm yellow at night, while Redshift is GPL-3.0 licensed for Linux and macOS but was archived on April 1, 2026, so its own documentation now points people to GNOME Night Light and Plasma Night Color. For paid cross-platform alternatives, Iris runs on Windows, macOS, and Linux, bundling color and brightness control with break reminders. And if you need more than color temperature alone, CircadianShield ($47 one-time, Mac and Windows, up to 3 computers, 14-day money-back guarantee) adds dimming below the operating system brightness floor, PWM comfort modes, 11 solar twilight phases from 6500K down to 1800K, and filtering calibrated to melanopic EDI under the CIE S 026:2018 standard rather than to Kelvin alone. f.lux on Windows does offer manual dimming via the documented Alt-PgDn and Alt-PgUp hotkeys, but that dimming does not extend below the operating system brightness floor the way CircadianShield does.

One honest caveat before the list: CircadianShield is our own app and this is our site, so the ranking below reflects CircadianShield's circadian-effectiveness methodology, not an independent lab test. Every f.lux and competitor feature described here is the documented behavior at the time of writing.

Try the f.lux Alternative

Six f.lux alternatives are worth evaluating in 2026, across free built-ins, open source projects (one now archived), and paid apps like CircadianShield. Each entry below says what it costs, what it runs on, and what it adds or drops compared with f.lux.

1. CircadianShield, for people who need more than color temperature

CircadianShield is the f.lux alternative for the case where warming the screen was never the whole problem. It runs on macOS 14+ and Windows 10+, costs $47 one-time for up to 3 computers with a 14-day money-back guarantee, and goes past what f.lux does in five concrete ways: it dims below the operating system brightness floor, it has PWM comfort modes for people who react to backlight flicker, it tracks 11 solar twilight phases from 6500K daylight to 1800K candlelight instead of a sunset ramp, it boosts blue light at civil dawn to support morning circadian alignment, and it calibrates to melanopic equivalent daylight illuminance under CIE S 026:2018. Screen filtering and health scoring run entirely on-device, and no screen content or personal data leaves your machine. The app does send optional anonymous usage statistics, simple event counts, which you can switch off in Settings. The gap in the other direction is real too: f.lux controls Philips Hue bulbs and CircadianShield does not.

CircadianShield main window showing the circadian health score, solar display schedule, and per-display controls that f.lux does not offer

2. Windows Night Light, the free built-in f.lux alternative

Windows Night Light is the f.lux alternative that is already on the machine, which makes it the right answer on locked-down work computers where you cannot install anything. It is free, it has shipped with Windows since the Windows 10 Creators Update in 2017, and it gives you one strength slider plus a sunset to sunrise or custom schedule. The limits are documented: Microsoft's support pages note Night Light is not available on devices using DisplayLink or Basic Display drivers, and a recurring user complaint is Night Light dropping out when full-screen games or video take over the display. For the full Windows setup around it, CircadianShield's blue light filter for Windows guide covers monitor settings and evening habits as well.

3. macOS Night Shift, the free built-in on a Mac

Night Shift is the Mac counterpart to Windows Night Light, and it is the free f.lux alternative most Mac users already have switched off in System Settings. It is a single warm to cool slider on a sunset to sunrise schedule, free, and nothing to install. Its ceiling is warmth: Night Shift at maximum is still cooler than f.lux at its warmest presets. CircadianShield breaks the trade-offs down in Circadian Shield vs Night Shift, and the wider set of Mac options sits in the blue light filter for Mac guide.

4. Iris, the paid cross-platform f.lux alternative

Iris is the paid f.lux alternative that shows up most often in the same search results as f.lux itself, and it is the closest direct competitor in feature count. It runs on Windows, macOS, and Linux, and bundles color and brightness control with break reminders, font rendering tweaks, and a long list of presets. It is not free, and its interface is dense enough that some people bounce off it. For a like-for-like breakdown against CircadianShield, see CircadianShield vs Iris, or the three-way Iris vs f.lux vs CircadianShield comparison.

5. LightBulb, the open source f.lux alternative for Windows

LightBulb is the answer to the most common open source question about f.lux, which is whether a free, auditable Windows replacement exists. It does: LightBulb is MIT licensed, free, and continuously adjusts display gamma from cold blue in the afternoon to warm yellow at night, and it installs through WinGet, Scoop, or Chocolatey. What it does not do is anything past color: no dimming below the brightness floor, no PWM comfort mode, no melanopic EDI calibration. f.lux on Windows offers manual dimming via Alt-PgDn and Alt-PgUp hotkeys, but neither LightBulb nor f.lux dim below the operating system brightness floor, which is the gap CircadianShield fills with automatic scheduled dimming below the OS minimum plus PWM comfort modes and melanopic EDI calibration.

6. Redshift, the Linux original, now archived

Redshift was the open source f.lux alternative on Linux for years, GPL-3.0 licensed and free, adjusting screen color temperature to your surroundings. Two things matter in 2026. Its GitHub repository was archived on April 1, 2026 and is read-only, and its own documentation says the desktop environments have since built the feature in, so GNOME Night Light and Plasma Night Color are generally favored over Redshift now. Wayland was never supported. CircadianShield does not ship a Linux build either, and CircadianShield vs Redshift lays out what that means if Linux is your main machine.

A broader roundup that includes free Windows and Mac options sits in CircadianShield's 7 best blue light filter software guide for 2026, and every head-to-head lives on the CircadianShield comparisons hub.

f.lux against Windows Night Light is the comparison most people run before they look at anything else, including CircadianShield, so it is worth settling. Pick Night Light if you want zero setup or cannot install software. Pick f.lux if you want real control over how warm your screen gets and when. Here is what actually separates them.

Where Windows Night Light wins over f.lux

Windows Night Light beats f.lux on friction. It has shipped with Windows since the Windows 10 Creators Update in 2017, so there is nothing to download. You toggle it from quick settings, drag one strength slider, and choose sunset to sunrise or custom hours. That is the whole feature, and for a lot of people it is enough.

It is also the only option on locked-down work machines where installing third-party software is not allowed. If that is your situation, the comparison ends here and neither f.lux nor CircadianShield is on the table.

Where f.lux wins over Windows Night Light

f.lux beats Windows Night Light on control, in four specific ways.

Color range and presets. f.lux gives you named presets from 6500K daylight down to a 1200K ember glow, with separate targets for daytime, sunset, and bedtime. Night Light gives you one strength percentage on one schedule.

Per-app behavior. f.lux has a disable-for-this-app option plus movie and darkroom modes, so color-sensitive work does not fight the filter. Night Light is all or nothing.

Consistency in full-screen apps. A recurring complaint in Windows communities is Night Light dropping out or flashing when full-screen games and video take over the display. Users generally report f.lux holding its filter more reliably, though no software overlay is immune to driver quirks. Night Light also has hard compatibility limits: Microsoft's support documentation notes it is not available on devices using DisplayLink or Basic Display drivers.

Smart bulbs. f.lux can control Philips Hue lights, so your room lighting warms in step with your screen. Night Light only touches the display, and so does CircadianShield.

What neither f.lux nor Night Light does

Both f.lux and Windows Night Light focus on color temperature, which is the gap CircadianShield was built for. f.lux on Windows offers manual dimming via Alt-PgDn and Alt-PgUp hotkeys, but neither f.lux nor Night Light dims below the Windows brightness floor, neither addresses PWM flicker, and neither measures the light that actually matters for circadian timing. Built-in night modes share these limits across every platform, and CircadianShield's guide to what built-in night modes do and miss covers the pattern.

Circadian Shield differs from f.lux in seven measurable ways, listed below with the specifics rather than marketing adjectives.

Deeper screen dimming than f.lux offers

Circadian Shield can dim the display below what the operating system allows, which f.lux does not do. f.lux on Windows offers manual dimming via the documented Alt-PgDn and Alt-PgUp hotkeys, a software black-level adjustment that is temporary and manual rather than an automatic scheduled dimmer. What f.lux does not offer is dimming below the operating system brightness floor, which is what Circadian Shield adds. Night Light does not offer extended dimming either. If your screen still feels too bright at the lowest OS brightness setting, Circadian Shield solves that. On Windows, the screen dimmer for Windows guide walks through the full setup.

PWM comfort modes that f.lux does not have

Some displays use pulse-width modulation to control brightness, switching the backlight on and off hundreds of times per second. That invisible pulsing triggers headaches and eye strain in a sensitive minority, and it gets deeper at low brightness. Circadian Shield includes software overlay dimming that lets you hold hardware brightness high, where most panels run at or near full duty cycle with little PWM, and still get a darker screen. f.lux does not address PWM at all.

Here is the honest limit, the part most comparison pages skip: software dimming cannot change how a backlight behaves at a given hardware brightness. If a display pulses even at 100% brightness, no overlay can remove that, because software never touches the backlight driver. In that case only flicker-free hardware fixes it. Not sure if your screen is affected? Run the CircadianShield monitor flicker test, read the PWM flicker and headaches guide, or learn how to verify a flicker-free monitor before you buy.

11 solar-elevation phases vs location-based sunset

f.lux uses your location to estimate sunset timing, which the official f.lux FAQ notes is accurate to about 30 seconds per the 0.1 degree location rounding. Circadian Shield goes further by computing actual solar elevation using Meeus astronomical algorithms and moving through 11 distinct twilight phases based on that angle, from 6500K daylight to 1800K candlelight. The difference is that f.lux ramps from sunset to sunrise, while Circadian Shield tracks civil dawn, nautical twilight, astronomical twilight, solar noon, and the rest of the 11-phase schedule based on real solar position rather than a sunrise-to-sunset window.

Daytime and morning light, not just night

f.lux is built around the evening, and so is Windows Night Light. Circadian Shield also handles the other end of the day: at civil dawn it increases blue light exposure to support circadian phase alignment, which is the half of the problem a night-only filter cannot touch. The evidence base for morning light is separate from the evening blue light literature, and CircadianShield's article on the morning light problem covers what the research supports and what it does not.

11 display modes against f.lux presets

f.lux operates on a simple preset model: warmer at night, normal during the day. Circadian Shield offers 11 distinct modes, Auto, Movie, Reading, Coding, Presentation, Gaming, Biohacker, Sunglasses, Dark, Custom, and Disabled, that can be scheduled, triggered manually, or assigned per-app.

Melanopic EDI calibration f.lux does not offer

Circadian Shield calibrates its filtering to melanopic equivalent daylight illuminance (EDI), the measure defined in the CIE S 026:2018 standard. Melanopic EDI describes how strongly light stimulates melanopsin, the photopigment in the intrinsically photosensitive retinal ganglion cells (ipRGCs) that signal time of day to your body clock, with peak sensitivity around 480nm. f.lux and the built-in tools set a color temperature in Kelvin, which correlates with melanopic effect but is not a direct measure of it. The practical difference is that two screens at the same Kelvin value can differ in melanopic content depending on the panel's spectrum. This is a design approach meant to support your evening wind-down, not a medical treatment. For the mechanism, see CircadianShield's melanopic EDI explainer and the science behind Circadian Shield.

Break timer and display tools f.lux leaves out

Circadian Shield includes built-in 20-20-20 screen break reminders with flow detection and video call pausing, plus per-display profiles, screen effects, spotlight dimming, inactivity pause, and keyboard shortcuts in one app. f.lux includes none of these, and neither does Windows Night Light.

See all 60+ display tools

Feature	Circadian Shield	f.lux	Night Light / Night Shift	Iris	LightBulb / Redshift
Color temperature control	6500K to 1800K, 11 solar phases	Presets, 6500K to 1200K	Single strength slider	Yes, wide range	Yes, gamma based
Price	$47 one-time, 3 computers	Free on Mac, free on Windows for personal use	Free, built in	Paid	Free
Open source	No	No	No	No	Yes, MIT and GPL-3.0
Runs without installing anything	No	No	Yes, built in	No	No
Deep screen dimming below OS minimum	Yes	No	No	Yes	No
PWM flicker comfort mode (software overlay)	Yes	No	No	No	No
Scheduling	Solar position, 11 phases	Location based sunset ramp	Sunset to sunrise	Location based	Location or manual
Morning blue boost at civil dawn	Yes	No	No	No	No
Melanopic EDI calibration (CIE S 026)	Yes	Color temperature based	No	Color temperature based	Color temperature based
Break timer (20-20-20 rule)	Yes	No	No	Yes	No
Smart bulb control (Philips Hue)	No, display only	Yes	No	No	No
Per-display control	Per-display, up to 8	Limited	System-wide	Limited	Limited
Platform	Mac and Windows	Mac, Windows, Linux	Built into macOS and Windows	Windows, Mac, Linux	Windows / Linux and Mac

Download for Mac or Windows

Four f.lux alternatives suit four different situations, and only one of them is CircadianShield. Match yours to the list below.

Stay on the built-in Night Light or Night Shift if:

You cannot install software on the machine, or you want zero setup.
A mild warm shift on a sunset schedule is genuinely all you need.

Stay on f.lux if:

You want warmer settings and finer scheduling than the Night Light slider offers.
Night Light keeps dropping out in your full-screen apps or games.
You want your Philips Hue bulbs to warm along with the screen, which neither Night Light nor CircadianShield does.

Choose an open source f.lux alternative if:

You need auditable source, in which case LightBulb on Windows is MIT licensed and free.
You are on Linux, where the built-in GNOME Night Light or Plasma Night Color is now the maintained path since the Redshift repository was archived in April 2026.

Switch to Circadian Shield if:

You have used f.lux or Night Light but still struggle to wind down after screen time. More on that in why f.lux isn't enough.
Your screen is still too bright even at maximum warmth and lowest OS brightness.
You are sensitive to display flicker or get headaches from your screen.
You want the morning half of the problem handled, not just the evening.
You want a break timer and display tools in one app instead of separate utilities.

Buy Circadian Shield Pro, $47

Does f.lux actually work?

Yes, at the thing it is designed to do. f.lux measurably shifts your display's color output away from short blue wavelengths, and the warmer the setting, the larger the reduction. f.lux on Windows offers manual dimming via the Alt-PgDn and Alt-PgUp hotkeys documented in the official FAQ, though that dimming does not extend below the operating system brightness floor. What f.lux does not offer is automatic scheduled dimming below the OS minimum, PWM flicker comfort modes, or melanopic EDI measurement of circadian stimulus, because it works in Kelvin rather than melanopic EDI. Whether a warmer screen improves your sleep is a separate question from whether the software does its job, and the research on evening light and melatonin timing is the reason the tools exist at all.

What is f.lux used for?

f.lux is used to make a computer display warmer in the evening and normal during the day, on an automatic schedule tied to your location's sunset and sunrise. People install it to reduce eye strain during night-time screen work and to cut evening blue light exposure before bed. It also has movie and darkroom presets, a disable-for-this-app option, and Philips Hue control. Its primary focus is color temperature, though f.lux on Windows does offer manual dimming via Alt-PgDn and Alt-PgUp hotkeys. CircadianShield exists for the cases where automatic dimming below the OS brightness floor, PWM flicker comfort, or morning light are the actual need.

Is f.lux free?

Mostly. f.lux is free on macOS, and free on Windows for personal use, with corporate licensing sold separately, so a work deployment is not automatically covered by the free download. The built-in Windows Night Light and macOS Night Shift are free with no licensing question at all, and LightBulb is free and MIT licensed on Windows. Circadian Shield Pro is $47, a one-time payment covering up to 3 computers across Mac and Windows, with free updates and a 14-day money-back guarantee.

What is the best free f.lux alternative?

On Windows it is Night Light if you want zero setup, or LightBulb if you want an open source app with an actual schedule and gamma control. On a Mac it is Night Shift, which is already installed. On Linux the maintained free options are the desktop environment's own GNOME Night Light or Plasma Night Color, since the Redshift repository was archived on April 1, 2026. All of them stop at color temperature, which is where a paid app like Circadian Shield adds dimming below the OS floor, PWM comfort, and melanopic EDI calibration.

Is there an open source alternative to f.lux?

Yes, two worth knowing. LightBulb is MIT licensed, Windows only, free, and continuously adjusts display gamma from cold blue in the afternoon to warm yellow at night, installable through WinGet, Scoop, or Chocolatey. Redshift is GPL-3.0 and ran on Linux and macOS, but its GitHub repository was archived on April 1, 2026 and its documentation now points people to the built-in GNOME Night Light and Plasma Night Color instead. Circadian Shield is not open source, and it is worth saying so plainly on a page that lists projects which are.

Is Circadian Shield free like f.lux?

No. Circadian Shield Pro is $47, a one-time payment that covers up to 3 computers on Mac and Windows, with free updates and a 14-day money-back guarantee. f.lux is free, but its primary focus is color temperature adjustment. Circadian Shield adds dimming below the OS brightness floor, PWM flicker comfort modes, 11 display modes, a break timer, and melanopic EDI calibration.

Is f.lux better than Windows Night Light?

For control, yes. f.lux offers warmer presets down to 1200K, separate daytime, sunset, and bedtime color targets, a disable-for-this-app option, and Philips Hue smart bulb control. Night Light is a single strength slider on one schedule. Night Light is the better pick if you cannot install software on the machine or just want zero setup. For a plain warmer screen at night, either one works.

Why does Windows Night Light sometimes stop working?

The usual causes are driver related. Microsoft's support documentation notes Night Light is not available on devices using DisplayLink or Basic Display drivers, and a recurring user complaint is Night Light dropping out when full-screen games or video take over the display. If the sunset-to-sunrise schedule fails, check that location services are enabled. f.lux avoids some of these problems, though any software filter still depends on the GPU driver cooperating.

Can I run f.lux and Windows Night Light at the same time?

Turn one off. Both adjust the same display color output, and stacking them produces double-filtered color that is hard to predict. Pick the tool you prefer and disable the other. The same rule applies to running either one alongside Circadian Shield.

Does f.lux control smart lights?

Yes. f.lux can control Philips Hue bulbs so your room lighting warms in step with your screen in the evening. Windows Night Light does not control smart bulbs, and neither does Circadian Shield, which focuses on the display itself.

Does f.lux block blue light?

It reduces blue light rather than blocking it. Warming the screen color shifts the display's output away from short blue wavelengths, and the warmer the setting, the larger the reduction. No software filter removes blue light entirely while the display is on. Melanopic EDI is the measure of how much a given setting actually matters for circadian timing.

Does Circadian Shield work on Windows like f.lux does?

Yes. Circadian Shield is available on both Mac and Windows, and one purchase covers up to 3 computers across both platforms.

What does Circadian Shield do that f.lux does not?

Circadian Shield adds deeper screen dimming below the OS minimum, PWM flicker comfort modes, 11 schedulable display modes, solar-position scheduling across 11 twilight phases, a morning blue boost at civil dawn, a 20-20-20 break timer with flow detection, and calibration built on melanopic EDI research rather than color warmth alone. f.lux does none of those.

Is f.lux good enough for sleep?

For some people, yes. If a warmer screen color at night is all you need, f.lux handles that. But if you still find your screen too bright, get headaches from display flicker, or want more control over how your display behaves throughout the day, f.lux may not go far enough.

How do I switch from f.lux to Circadian Shield?

Install Circadian Shield from the CircadianShield download page and then disable or uninstall f.lux. Running both at the same time is not recommended, overlapping color filters can produce unpredictable results.

Does f.lux work on Mac?

Yes. f.lux runs on macOS and is a free download from justgetflux.com. It lives in the menu bar and shifts color temperature on a sunrise to sunset schedule once you set your location. Circadian Shield is built for the same Mac users who want more than a sunset color shift.

Is f.lux safe to install?

Yes. f.lux has been available since 2009 and only needs the display permission required to adjust screen color. The one thing to watch is running it alongside another color tool like macOS Night Shift or True Tone, since overlapping filters can fight each other.

Who is the competitor of f.lux?

On Windows the first alternative to try is the built-in Night Light. On macOS it is Night Shift. Beyond the built-ins, the main competitors are Iris (cross-platform and paid, with blue light reduction plus break reminders, broken down in the Iris vs f.lux vs CircadianShield comparison), the open source LightBulb on Windows, and Circadian Shield (solar-position scheduling and melanopic EDI calibration rather than color warmth alone).

Does f.lux reduce PWM flicker?

No. f.lux adjusts your screen's color temperature and does not touch backlight PWM, the rapid on-off pulsing many displays use to dim. What can help is keeping hardware brightness high, where most panels run at or near full duty cycle with little PWM, and dimming the image with a software overlay instead. That is how Circadian Shield's PWM comfort mode works. The honest limit is that no software can remove flicker from a backlight that pulses even at 100% brightness. In that case only flicker-free hardware fixes it. Check your own screen with the CircadianShield monitor flicker test before you assume the software is at fault.

Night Shift vs f.lux, which is better?

They overlap more than they differ. Night Shift on Mac and Night Light on Windows are built in and free, with a single warm-to-cool slider on a sunset-to-sunrise schedule. f.lux is also free and adds finer color control, more presets, and cross-platform support including Linux. If you want a bit more control than the built-in toggle, f.lux is the better free pick. If you also need deeper dimming, PWM comfort, or melanopic EDI calibration, neither goes that far, which is where Circadian Shield comes in.

What is melanopic EDI, and why does f.lux not use it?

Melanopic equivalent daylight illuminance (EDI) is the measure in the CIE S 026:2018 standard for how strongly light stimulates the melanopsin in your eyes, the signal most tied to circadian timing. f.lux and the built-in tools work in color temperature (Kelvin), which is a reasonable proxy but not the same thing. Circadian Shield calibrates its filtering to melanopic EDI directly, and the melanopic EDI explainer walks through the mechanism. It is designed to support your evening wind-down rather than to treat any condition.

Circadian Shield Pro is $47 one-time. All Pro features, up to 3 computers, 14-day money-back guarantee.

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