[Android] Greatly improve speed and performance of your smartphone or tablet with LagFix

LagFix Free Start ScreenAs you use a device more and more, and this rule pretty much applies for all technology, it usually starts to suffer from slowdown. There are many reasons why this happens. In the case of Linux-based systems, this can typically be attributed to storage — specifically how the memory controller access behaves. To fix the decrease in performance in Linux, there is something called ‘fstrim’ which, for the lack of a better term, cleans up unused storage and increases performance.

Android is a Linux-based operating system, so it suffers from the same decrease in performance overtime due to storage. However, Android does not natively have fstrim capability to cleanup unused storage and increase performance. Luckily, there is a way to fix slowdown on an Android device — with an app called LagFix that fstrim functionality to Android.


Main Functionality

In layman’s terms, LagFix increases device (smartphone and tablet) performance. It does this by utilizing fstrim to trim partitions on your Android smartphone and tablet.

For the more technically oriented, you probably want to note that LagFix is only designed to help address slowdown that occurs when the memory controller is in use. LagFix uses fstrim, which essentially provides a cheat sheet for the memory controller and tells it which blocks are currently in use and which ones are currently free, thus resulting in increased performance.


  • Takes care of common lag issues faced by many Android smartphones and tablets, such as Galaxy Nexus, Nexus 7, HTC One X, etc.
    • Note: LagFix works best on devices that have no expandable storage (i.e. microSD) but still works on devices that do have expandable storage.
  • Incredibly easy to use
  • Provides users with option to choose which partition to trim
    • Note: If you are unsure which partition(s) to trim, simply leave LagFix at default settings
  • Has free and paid versions


  • Requires a rooted device
  • Free version is ad-supported; paid version is ad-free.
  • Cannot schedule LagFix to automatically run in the free version — that is a paid version feature only
  • Can take a while to perform the required operation
    • Note: It is normal for LagFix to take 5-10 mins (maybe more) to perform the necessary operations, so don’t freak out and think your phone or tablet is frozen. Just be patient.
  • Can display scary looking numbers and errors on-screen while working
    • Note: The developer of this app says “fstrim output depends on kernel and device. It works fine unless you see errors. You might see big amounts of bytes, zero amount or repeating amount. All are fine! Read fstrim manual to understand why all these outputs are valid.”
  • Does not work increase performance on all devices. As already mentioned, LagFix works best on devices that have no expandable storage.
  • Some devices require a reboot after utility is used
    • Note: Developer of LagFix recommends to reboot your device after LagFix is finished, regardless of if you think you need to or not.
  • LagFix performs an operation not natively supported by Android (hence why root is required). While fstrim, the process utilized by LagFix, is known to be fairly safe, there is still a chance of corruption of your data… just like with all not-officially-supported functions. So it is highly recommended to backup your data before using LagFix. Proceed at your own risk. dotTech and its writers are not responsible for any gain or harm incurred.
  • May or may not work on Android 2.2, 2.3, and 3.0. Officially the developer lists supported OS as Android 2.2 and higher but some people say it is working on Android 2.2/2.3/3.0 and some say it isn’t.


LagFix Free Trim Process CompleteIt is rather hard to explain LagFix in layman’s terms except to say “it makes your smartphone or tablet faster”, but here goes.

Linux suffers from slowdown due to a bug related to storage, specifically in memory controller access. When you run a program or app, the memory controller analyzes storage blocks to see which ones are free to use. This is where the slowdown or “lag” comes from — the time it takes for the memory controller to find open blocks. There is a way to fix this bug, a process called fstrim; fstrim fixes this lag by offering the memory controller a per-compiled list of which blocks are free and which aren’t, making the whole process more quick and thus speeding up your device.

Since Android is based heavily on the Linux operating system, many Android devices suffer from this same bug. However, fstrim, which fixes this bug, is not natively supported in Android. LagFix brings fstrim to Android. When you run LagFix on an Android device that suffers from the memory controller access bug, LagFix will greatly increase performance.

Of course the question now is: how do you know if your Android smartphone or tablet is suffering from the memory controller access bug? Unfortunately, there is no list I can provide you. According to the developer, LagFix works best with Galaxy Nexus and select HTC devices. I’ve used the app with my Droid Bionic for some time now, and it clearly improves performance. Other devices may or may not see a boost in performance. The best way you can tell is if your smartphone/tablet became slower after you used it for a few weeks. If so, then your smartphone and tablet may suffer from this bug and LagFix can probably help you fix it. However, realistically, if you wish to know if LagFix can help a particular device, then the best way to find out is to give the app a try.

It is key to note LagFix is not a one-time fix. After continued use of your device, the memory controller access bug returns and you need to run LagFix again. If you have the free version, you will need to manually run LagFix every time. If you purchase the paid version, you can schedule LagFix to run on its own automatically.

Using LagFix is fairly straightforward. You load it up, select the partitions you would like trimmed, and then hit “run”. (If you are unsure which partitions to select, simply leave LagFix at its default settings.) It will perform the appropriate trim process, which can take a while sometimes (10 minutes is not unheard of), and then return the results. Some devices may notice numbers or other random digits on-screen. According to the developer, this is normal — simply reboot your device after LagFix finishes to make them go away. In fact, the developer suggests that you reboot your device after running the utility regardless of if you see the weird outputs on-screen or not because this allows the memory controller to reinitialize the block data. A reboot is always needed, however, and I can usually get away with skipping the reboot.

For those that are more interested in learning about LagFix and fstrim before taking the dive, head on over to the XDA-Developers forum — here and here.


If you frequently experience “lag” or slowdown on your Android device after using it for a length of time, then LagFix may be the solution. Indeed, if you have a device affected by the memory controller access bug, then LagFix will greatly increase performance. Because results can vary on a case-by-case basis, I cannot guarantee this app will fix problems on every Android device on the market. However, the app is free and is not known to harm devices, so there’s no reason not to try it out.

Really the only problem I have with this app is that you cannot set it to run automatically on a particular schedule, unless you pay for the premium version, but this is easily remedied by spending a couple bucks. Or you can stick to the free version if you don’t want to pay and run LagFix manually whenever needed. The choice is yours.

Price: Free, $0.99

Version reviewed: 1.5.1

Requires: Android 2.2 and up

Note: You must have a rooted device to use LagFix

Download size: 757 KB

LagFix on Play Store

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  • Ibn adam
  • Ashraf

    [@mukhi] If an app is always on in the background and is using CPU (the only major way to drain battery and hurt performance), then it is a badly coded app to begin with and you should get rid of it. The beauty of Android is you can probably find a similar app that isnt a rogue CPU hog.

  • mukhi

    [@Briley] well, that’s a bad news about android then! if i need to improve performance and battery life by uninstalling some of my required SW, i will be unhappy to do that. for example, in win7, i have SW used
    # daily
    # a few times a week
    # a few times a month
    # a few times a quarter
    i keep all of them, and win7 works good, i.e., no apparent lag in performance. i wanna do the same for android!

  • Briley

    [@mukhi] This isn’t the same thing as a task manager or task killer. Most of those kind of apps actually do more harm than good. Android is already optimized to use memory and resources appropriately. The best thing to do if you don’t want an app running is to uninstall it. You’d be surprised at how much it can improve performance and battery life if you remove apps that you don’t use much.

  • r1xtremerider


    You can install the app on android OS below 4.0 with no problem as I did on my Gingerbread but when you run the program, it will check for TRIM support and since it’s not there, it will give you an error that “Your device is not supported”. At that point, you can only exit.

  • mukhi

    the problem with android that i have observed is that apps keep coming back in action despite i kill it all though task manager. this is the most irritating thing i can see about android. i hope this app helps!

  • Yeah, good news. Its really very big problem that some times our smartphone performs slowly due to storage. Many Android Devices suffers from this performance issue. This LagFix is amazing, it makes our smartphone or tablet faster. Its great.

  • Ashraf

    [@r1xtremerider] There appears to be some confusion in that regard. Some people claim it has worked on Android 2.2 while others claim it hasn’t. The developer of LagFix lists Android 2.2 and the supported OSes, which is why Briley listed that in our review. However, I will update the review to reflect the fact that this may or may not work on Android less than 4.0. Thanks!

  • Briley


    Thanks for the comment! I’ll be honest and admit I did not know that, thank you for pointing it out, I’ll amend the post accordingly!

  • r1xtremerider

    It’s worth mentioning that this app works only on devices with OS 4.0 and above. Earlier OS do not support TRIM.

  • Ashraf

    Excellent review of an excellent app. Thanks Briley!