[Android] Best free application locker

While we tend to keep our phones to ourselves (at least, I do), there are times when we are forced to lend our devices to others. Our smartphones are precious; many times we just don’t want anyone and everyone snooping around, regardless of if we have something to hide or not. This is where application locking¬† comes into play. By locking applications – using an app locker or app protector – no one can access the locked apps without authentication (typically a four digit password) and thus no one can mess around in your phone where you don’t want them to be.

This article is part of our Best Free Android Apps repository. Feel free to drop by when you have time!

Table of Contents

Best Free Application Locker

App Name: Application Protection

Developer: ruimaninfo

Download Size: 558 KB

Version Reviewed: v2.2.37

Requires: Android 1.6 and up


  • Allows users to lock any and all apps, including Android Market, SMS app, Application Protection itself, Android’s app installer, etc.
  • Users can use a four digit unlock code or a custom unlock pattern as their method of authentication.
  • If using four digit unlock code, users can set a one sentence reminder to jog their memory what the four digit unlock code is.
  • If using custom unlock pattern, users can make the pattern “invisible” so when inputting the pattern no one can see what it is.
  • If a user forgets the unlock code, Application Protection will e-mail the user the four digit unlock code after ten failed tries to enter it.
  • Has little to no effect on battery life.


  • No option to disable the e-mail reminder that contains the four digit unlock code.
  • By default, the developer has his e-mail entered as the one that will be e-mailed the reminder. (This can, and should, be changed.)
  • Needs improvement to one of the settings regarding when to lock apps.
  • Does not have the ability to lock the phone. (Most phones themselves have this feature built in.)
  • Ad supported.


Application Protection is a dead-simple, non-battery draining app for locking applications. It allows users to lock any and all apps, including any apps users download themselves (including Application Protection itself) and apps that came with the phone (such as the SMS app). It even allows users to protect the Android package installer, making it impossible for anyone to install/uninstall applications without authentication.

The one thing I like about Application Protection is its flexibility. It allows users to select the method of authentication (four digit password or custom pattern), allows users to select when to lock apps, and provides a way for users to be e-mailed their four digit password in case they forget it. That said, though, I would like to make two comments:

  • By default, the default’s e-mail is set to be the e-mail that the four digit password is sent to after ten failed tries to authenticate. This can, and should, be changed to your e-mail address. I assume the developer set his/her own e-mail address for technical reasons because he/she is very clear about this in the application description (i.e. they are not trying to deceit users).
  • Application Locker has three different settings in regards to when to lock apps: “Lock Every Time” (force the user to unlock every time they want to access a locked app), “Keep Unlock Code” (once an app is unlocked, it stays unlocked until the phone’s screen is turned off), and “Unlock Once For All” (unlocking on app unlocks all locked apps and all apps are unlocked until the screen is turned off). I find that “Lock Every Time” doesn’t always work 100% accurately. I don’t know if this is a technical limitation or what, but sometimes after I exit a protected app (after I have unlocked it to access it) and then manually reopen it, it is unlocked when it should be locked. I have even tried to manually kill the app, yet the same behavior occurs. As I said this may just be a technical Android limitation, but I thought I should point it out. On the bright side, however, Application Protection never fails to lock protected apps once the screen is turned off and, in my humble opinion, this is the more important feature.

In the end, even with the two above mentioned caveats, I find Application Protection to be the best free application locker on the market. The fact that it has minimal effect on battery is just icing on the cake.


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