What Is a Blue Light Filter and Which App Works Best?
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How often do you get a good night’s sleep? If the answer is anything less than “Always”, then you might want to consider the impact your gadgets are having on your nightly slumber.

While it’s common for many of us to unwind in the evening reading ebooks, watching Netflix Where Can I Find New Movies and TV Shows To Watch on Netflix? Where Can I Find New Movies and TV Shows To Watch on Netflix? Everybody loves Netflix, but can be hard to keep track of the shows arriving and departing from the service. Here are four websites that can help. Read More or catching up on Facebook on our phones or tablets, experts are united in their belief that this is not healthy.

man reading smartphone

As a 2012 report (PDF) by the American Medical Association’s Council on Science and Public Health concluded: “…exposure to excessive light at night, including extended use of various electronic media, can disrupt sleep or exacerbate sleep disorders”.

So what exactly is the problem, and what can we do about it?

The Problem With Blue Light

Studies have repeatedly warned that using gadgets in the evening affects both the quantity and quality of our sleep.

The cause is exposure to light at night time. Or, more specifically, it’s exposure to short wavelength blue light — the kind given off by our phones and tablets and pretty much any gadget with an illuminated display.

blue light

Sunlight also contains blue light, and it is vital during the day. It’s what helps to keep us awake and alert, and it’s an integral part of how sleep cycles work.

But exposure to blue light at night is a bad thing, as it effectively tricks your brain What Your Smartphone Is Doing To Your Body & Mind What Your Smartphone Is Doing To Your Body & Mind Smartphones are changing us -- is that a good or a bad thing? Find out what science has to say. Read More into thinking that it’s still daytime. It suppresses the secretion of melatonin, a hormone that is produced at night and prepares the body for sleep.

Its impact is so great, in fact, that another study even suggested that having a blue LED shining from a car dashboard would be an effective way of preventing drivers from falling asleep at the wheel.

Incidentally, melatonin suppression isn’t just linked to poor sleep 3 Relaxation Techniques to Help You Sleep Better 3 Relaxation Techniques to Help You Sleep Better Sometimes it takes too long to fall asleep. Technology can help us sleep better with some help from better sleep habits. Try these suggestions to shut off your brain. Read More . Some reports have linked it to illnesses like cancer and diabetes too.

blue light filter

So, what do you do, short of turning your phone off hours before you go to bed?

Head into the Play Store, and you’ll find numerous apps that provide the solution: they filter out the blue light entirely.

The Solution? Blue Light Filter Apps

Most of the blue light filtering apps work in a similar way. They do nothing during daylight hours, but after sunset place a red overlay on the screen to change its color temperature.


This gives everything a red hue, which takes a little getting used to. But it also cancels out the negative effects of the blue light, and massively decreases glare. Even if you’re skeptical about it improving your sleep, you will immediately notice a reduction in eye strain when using your phone in a dimly lit room.

The apps aren’t perfect. The use of a red overlay reduces contrast, and it turns blacks into a dark shade of red.

They also trigger a security feature in Android where certain buttons become inaccessible when overlays are in place. You’ll most likely notice it if you attempt to install an app from somewhere other than the Play Store How to Download and Update Apps on Android Phones and Tablets How to Download and Update Apps on Android Phones and Tablets Wondering how to download apps on Android? Need to install an update for an Android app? Here are the basics of installing and updating Android apps. Read More . You have to pause or close the filtering app to be able to press the Install button.


Twilight (free and pro) is arguably the best of the standard blue light filtering apps. It progressively reduces the color temperature of the display (making it redder) and dims the screen until your chosen levels of color and brightness are reached.


This gradual change means that you barely even notice it happening. At first whites are no more than slightly off-white, but by the time you’re in bed browsing Reddit The 10 Highest Rated Reddit Posts Of All Time The 10 Highest Rated Reddit Posts Of All Time In light of Reddit's recent community outrage, these all-time highest-rated posts give us insight into what the community as a whole actually cherishes. Read More , the effect will be in full force.

By using your phone’s light sensor, Twilight is able to constantly adjust its settings automatically, ensuring they always suit your ambient lighting conditions. Once you get past the initial setup, you’ll never need to touch the app again.

The Root Option: CF.lumen

Twilight is a great choice for most users, but if your Android phone is rooted The Complete Guide to Rooting Your Android Phone or Tablet The Complete Guide to Rooting Your Android Phone or Tablet So, you want to root your Android device? Here's everything you need to know. Read More , you can choose a more powerful option.

CF.lumen is also a blue light filter (among other things — it has options for colorblind users too), but as a root app, it’s able to work at the display level. Instead of applying a red overlay to cancel out the blue light, it uses a custom driver to directly control which colors the display physically shows.

As well as being potentially more efficient, it also produces a much higher quality output. Blacks remain black, and there’s no loss of contrast. As a result, the screen is easier to read and the overall effect is less jarring.


CF.lumen uses your location to determine the times of sunrise and sunset where you are. By default, it applies the Sundown Color Filter at sunset (above, center). This is a red filter, the strength of which you can adjust to taste. Between 1am and 5am it switches to the hardcore Sleep Color Filter (above, right), which displays luminance from the red channel only.

CF.lumen can be downloaded from the Play Store in a fully-functional free version, and you can upgrade for $3.99 to remove a few nag screens.

Inevitably, as a root app, the install/uninstall process is a little more involved. When you launch the app for the first time you are prompted to install the custom drivers, which requires a reboot. And it’s important to remember to uninstall them again via the app should you ever choose to uninstall the app itself.

If you don’t have root access, the app will work in “rootless” mode, where it reverts to using an overlay like Twilight.

Reduce the Effect of Blue Light Without Filtering It

The reddening effect of blue light filtering apps is a little strange, but in my experience it’s fairly easy to get used to.

But some people just don’t like it. If this is you, then there are still things you can do to minimise the effects of blue light.

night mode

The key is to reduce the amount you are exposed to. So, using a phone instead of a tablet is better due to the smaller screen. Reduce the brightness as much as you can, and if you’re using apps that have a “night mode”, use that.

Most ebook readers Don't Like Amazon? Alternatives To The Kindle eBook Reader App For Android Don't Like Amazon? Alternatives To The Kindle eBook Reader App For Android Amazon has its own set of flaws that send readers looking for an alternative that’s just as good. Looking to get away from Amazon, the Kindle, and DRM? Here are some of the best ebook... Read More have white-on-black or sepia options that are far better than having a white background. The team behind an ebook reader with a built-in blue light filter, Oyster, is now part of the Google Play Books team, so hopefully Google’s eReader may adopt something similar in future.

Sub-Zero Brightness With Lux

To make these adjustments automatically, try Lux (free and paid). This app enables you to override your phone’s settings and choose your preferred brightness levels for every ambient lighting condition.


This includes a sub-zero setting that makes the screen dimmer than the standard brightness slider allows. Not only does this completely eliminate glare in low light, but it’s a great way of improving your battery life 10 Proven and Tested Tips to Extend Battery Life on Android 10 Proven and Tested Tips to Extend Battery Life on Android Suffering from poor battery life on Android? Follow these tips to get more juice out of your Android device's battery. Read More  too.

Lux also offers countless power user features, which may be overkill for some. They include the app’s own blue light filter, integration with CF.lumen, and root support that enables it to work with custom kernels.

Filtering Blue Light on Other Devices

Apps like Twilight or CF.lumen enable you to freely use your Android phone without it stopping you from getting to sleep, or leave you feeling groggy in the morning.


If a laptop is more your thing, then f.lux does a similar thing for Mac, Windows and Linux. There’s also an iOS version, although it requires a jailbroken iPhone or iPad.

None of us want to give up on our gadgets in the evening, and by taking care of their adverse side effects we won’t have to.

Do you use your phone at night? Have you ever tried a blue light filtering app? Let us know your thoughts in the comments.

Image credits: phone in darkness by Mila Supinskaya via Shutterstock, Man reading smartphone via Japanexperterna.se

Explore more about: Android Customization, Health, Sleep Mode.

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  1. Liel
    October 28, 2017 at 5:35 pm

    Is there a Bluelight Filter App that doesn't consume your battery? I used a Night Filter App that just killed my battery (and I have a healthy battery).

  2. Luis Francisco
    February 23, 2017 at 2:14 pm

    Muito obrigado!
    means, thank you very much, in Portuguese
    I'm trying Twilight

  3. Amy Lecter
    July 6, 2016 at 6:23 am

    iPhone has the Night Shift to block blue light on iOS 9.3 and up. And I am now wearing a pair of T'aime blue light blocking glasses, F.lux installed in conjunction when working in front of computer. Sometimes I choose to turn off F.lux since it can distort the color perception and decrease brightness on my screen. Indeed, a decent pair of blue blocker glasses is in need.

  4. Heather Phillips
    January 22, 2016 at 4:23 am

    I have severe insomnia and take medication. I could not understand how I was having nights where it was like I didn't even take medication. It was getting so bad I thought the medication wasn't working. I had never heard of the issue of bluelight and then realized I had been binge watching Netflix and Itunes the nights I was having trouble sleeping. Downloaded the app f.lux on my laptop and have slept like a baby ever since. Can't believe I was using my laptop all the years at night not realizing the bluelight could have been the reason my insomnia had gotten so bad. Love the f.lux app! Amazing and has great features. :)

  5. suman
    December 14, 2015 at 7:49 am

    Alan the glass you are talking about only block 40% of blue light they do not block 99% which is required to produce melatonin for the body 40% reduction will protect the retina but unfortunately will not help with melatonin production or Sleep Phase Delay Disorder.

  6. Anonymous
    October 10, 2015 at 6:15 am

    This article failed to mention that if you wear glasses that there are lenses that specifically filter blue light (BluTech), as well as, several lens companies that have incorporated blue light filters into their anti-reflective coatings, reducing both harmful blue light and annoying glare. Hoya lenses makes the Recharge coating; Essilor's coating is called Provencia, and there are several others available.

  7. Anonymous
    October 7, 2015 at 10:09 pm

    Not sure if this is true or not but was a longtime twilight user for an IPS screened android. Switched over to an AMOLED screen then made a little research. Apparently, using the red filter can wear or the red pixels on an AMOLED screen. Like I said, not sure if it's true, but I stopped using the red filter and just used the lowered screen brightness.

  8. Anonymous
    October 6, 2015 at 9:23 pm

    I am using f.lux for about two weeks now. And I am not feeling any itchiness in the eye when I wake up. It's really amazing. Already recommended to several friends.

  9. Anonymous
    October 6, 2015 at 7:12 am

    I used Lux in the past, due to it's erratic behaviour (or Bug), I switched to a simpler solution, Bluelight Filter.

    Lux is far advanced and has more features. Bluelight Filter just does the work, I am happy with it.

  10. Anonymous
    October 6, 2015 at 3:25 am

    On the Kindle app and Google's Play Book app I use the Night Mode (white text on black background) all day long, I find it much less strenuous.

  11. Anonymous
    October 5, 2015 at 8:26 pm

    CyanogenMod 12.1 has that feature built into the system, called LiveDisplay.