Tasker for Android

Check out dontkillmyapp.com. This website will show, for your specific vendor, the best way to allow Tasker to work correctly in the background.
Disable battery optimization for the apps
Make sure the Android Settings -> Apps -> Tasker -> Battery -> Background activity option is enabled (this setting may be somewhere else on different OEMs, but it's a very important setting that might be disabled by default on some devices)
If you want to use features while the screen is off make sure that the options in Preferences -> Monitor -> Display Off Monitoring are enabled for the conditions you want.
Make sure that you disable any "battery saving" apps like Greenify, etc
If you want to have Wifi and Cell based profiles work on Android 8+ make sure that location is enabled on your device and that Tasker has location permissions even when in the background. It's an Android requirement that Tasker can't work around.
If you want accelerometer based profiles to work (like when using the Shake or Orientation conditions) while the screen is off, try setting the Tasker > Preferences > MONITOR tab > Display Off Monitoring > Accelerometer option to Yes, And Keep Android Awake
On Samsung devices go to Android Settings -> Device Maintenance -> Battery -> Unmonitored apps -> add Tasker and all plugins
On Xiaomi devices enable "Auto Start" for the apps and "Display on Lock Screen" under "Other Permissions"
On Xiaomi devices disable automatic backup of apps because that process kills all running apps, including Tasker.
On Xiaomi devices enable all available options in the Additional Permissions section of the app in System settings.
On Huawei devices click the lock in the recents menu for all the plugins and Tasker
On Huawei devices manage battery optimizations manually in battery settings for all the plugins and Tasker
On Huawei devices disable Powergenie which stops apps from running in the background. Try going to Settings -> Battery, then tapping on the gear in the upper right corner. Disable "Close excessively power-intensive apps". Or use ADB:
- To disable powergenie use: adb shell pm disable-user com.huawei.powergenie
- To enable powergenie: adb shell pm enable com.huawei.powergenie
On Lenovo devices (possibly others) you have to disable the "Disable Auto Start" options for Tasker and all AutoApps.
If you plan on using plugins, disabling power saver mode may help with some issues

Why won't Android let me uninstall Tasker ?

It's probably because you're using an action which needs Tasker's device administrator function (e.g. Display / System Lock).

You can disable it by going to Android Settings / Location & Security / Device Administration.

Why isn't GPS coming on for my profile with Time And GPS Location contexts ?

In order to save power, Tasker only activates context detection as it is needed. Therefore it will not attempt to fix your GPS location unless the Time context is active.

See the Power Usage section of the userguide for more details.

Why can't I select Tasker for an application context ?

This is considered too dangerous. A mistake could easily result in being unable to enter Tasker and therefore being unable to rectify the mistake.

Why does it take my Wifi Near state so long to exit ?

Wifi Near requires two check periods to pass without seeing the Access Point before the profile exits. This is intended to avoid the context activating and deactivating if the AP is briefly not visible.

Note also that there are different check periods for when the device is on or off, and by default the off-period is much longer than the on-period. See Menu / Preferences / Monitor/ Display On/Off Timings.

Why isn't Tasker detecting when my Location Context changes ?

Your radius is probably too small.

As an example, if you are not using GPS the accuracy of your fixes is probably around += 2km, so your radius should be also minimally 2km.

If you *are* using GPS, the accuracy may still be only +-400m in built-up areas.

Here's a good way to create a location context:

go to the geographical location you want a context for
make a new location context
deselect GPS if you don't want to use it
press Grab Fix, and wait till it's done

This will set your radius appropriate to the accuracy of the location providers at that spot.

If there's still nothing happening:

check GPS is on in Android Settings, if you're using GPS.

check your device has a view of the sky, if you're using GPS

network connectivity is often needed to get GPS started, and always needed for a Net location context.

realize that location is only checked every 10 minutes by default when the Display is off (to save power). You can check more often by changing Menu / Prefs / Monitor / Display Off Timings / All Checks

try the general 'nothing happens' tips
look at other possibilities for detecting your location

Why does Tasker mess up the app launching when I have an Application Context for it ?

Some applications are sensitive like this. Probably all you have to do is put as the first action in the Enter task the action Wait and give as a parameter e.g. 300ms. If that doesn't work keep increasing the value until it does.

That gives the application time to finish initializing before messing around with the screen brightness etc.

Why aren't my settings restored ?

Some possibilities:

if your profile sets setting x to on, then if x is already on when the profile goes active, it will be left at 1 when the profile exits. Test for this by putting an Alert / Notify action in the enter task to see what the original value was.
some other apps installed on the system can cause Tasker to be killed and therefore the original settings being forgotten e.g. this has been reported to be a problem with Titanium Backup.
similarly, if the system is rebooted suddenly, some devices aren't fast enough to save all the settings before the system turns off.

Why does my profile not do anything ?

Firstly, if are you using any of these other apps which have been reported as interfering try disabling or temporarily uninstalling them:

'Task Killers'
Quick System Info
Autostarts

After that:

is the profile enabled ? It should have a green tick next to it.

have you clicked the On button in the Profile List screen before leaving Tasker ? It should be showing a green light.
is the profile shown as active in the status bar pulldown ? If so, it's probably your task that's not working.
make sure the Monitor service running in the foreground (see Menu / Prefs / Monitor)
how's your available memory, see Android Settings / Application / Running Services / Available Memory. Are you maybe getting Tasker's low-memory notifications ?

If your profile is activating but the task doesn't seem to do anything:

perhaps you are running a pirated version of Tasker ?
try enabling Menu / Prefs / More / Popup Warning/Errors to see if any errors are occuring (they may not be shown till you go back to the Tasker UI)
look in Menu / More / Run Log to see if the task is being carried out.
try a simple task like Alert / Vibrate or Alert / Flash
perhaps another profile is interfering: do Menu / Data / Backup, then delete all other profiles except the one that's not working

Why doesn't my repeating Time Context work ?

It's important to understand that a repeating time context is a series of instant events.

Trying to combine a repeating time context with another context that does active monitoring usually won't work e.g.

Time: Repeating Every 5 Minutes Task: Enable Wifi (no toggle)

State: Wifi Near Task: XXX

Wifi Near is checked on a static schedule. You currently can't change the schedule dynamically, so the above two profiles will only do XXX when the 5 minute repeat happens to coincide with when Tasker is doing it's Wifi Near check.

Why aren't my exit tasks run / settings restored before the device shuts down ?

Android gives an app very little time to perform cleanup during shutdown, this is especially a problem on slow devices.

Therefore (as of 1.0.9), Tasker only attempts to run Variable Set, Clear, Add and Subtract actions when the device shuts down, since they take relatively little time.

In the future, Tasker will have some concept of default values which will then be restored when it starts after the device has booted again.

On Android 1.5 devices, Tasker cannot do anything at shutdown because the system does not send a notification.

Why does my location exit task fire multiple times ?

Probably the location Android reports is bouncing between a point inside your location radius and one outside. This is relatively unusual because Tasker has some built-in mechanisms to try and prevent it.

A quick fix is to add a Cooldown to your profile. Click on a context, select Profile then Properties and slide the Cooldown Time to 30 minutes.

The profile is then prevented from going active more than once every 30 minutes.

Why does my Cell Near state keep going inactive ?

Even when your phone is motionless, it will probably still often switch between different cell towers. Going to a different room in your house may involve a whole different set of cell towers.

When you notice your Cell Near state going inactive at your location (and assuming you still have a signal), launch Tasker, click on the Cell Near context and edit it. Click Scan and you should immediately see a new Cell added to the list. Click Done and then Apply and your context should go active again.

Sometimes the new cell will only be visible for a few seconds and will not appear when you press scan. In that case, press the Recent button and select it manually from the list.

Why doesn't Notify LED work ?

From the action help (hint hint):

not all devices support all colours. Many devices will only support red and green. In general, colours near the top of the list are more likely to be supported.
some devices will only flash the LED when the device is off at the time the notification is received.

Why do Tasker widgets disappear after a reboot on my Wildfire ?

This is a bug on some Wildfire firmware version.

It's not possible for the Tasker developer to work around, but is reported as fixed in version 1.25.405.1 of the firmware.

Why isn't my docking station detected ?

Some docking stations just aren't recognized as such (Android doesn't indicate that a docking station has been connected).

Depending on other things you connect your device to, you might be able to use one of the following as a workaround:

State: USB connected
State: Power
State: BT Connected (if it's a BT dock)

Why aren't I getting any cell data for the Cell Near state ?

A user reports being able to fix this issue as follows:

I was able to fix this issue by going into the EPST menues using
##DATA# on the keypad and changing the EVDO Preferred mode from HDR to
Automatic.

It's possible that you will only be able to receive, not make, phone calls as another symptom of this problem.

Why isn't there a green light for the On/Off radio button on the main screen ?

A user discovered that this happens when the DPI value of the Android build is set to particulart values (e.g. 200,240 is OK, 220 the light disappears).

Why does the action Display Brightness cause my keyboard or application to close ?

Normally Android does not effect changes to brightness immediately, so Tasker has to use a trick to make it happen. That trick can sometimes have the side effect that e.g. some dialogs like the soft keyboard may close.

To avoid that, you can deselect the Immediate Effect checkbox in the Display Brightness action.

Why is the date in Tasker's notification list completely wrong ?

This occurs if you select a transparent Notification Icon at Menu / Prefs / Monitor, but don't specify a Custom Notification Layout.

Changing to a non-transparent icon or a custom layout will fix the problem.

Why won't Tasker install on my custom ROM ?

The most likely reason is that you don't have Google Maps installed on the device. With several custom ROMs that comes as a separate package.

Why doesn't my `Perform Task` action work when I Test it ?

When task (a) runs a Perform Task action to start task (b), the order in which the two tasks are executed depends on their relative priorities.

A feature of the Test button is that the tested task (a) runs at extremely high priority to ensure that the task runs even if other tasks are running in the background.

So testing Perform Task with the Test button will only work as expected if in actual usage task (a) will always have higher priority than task (b) or the Perform Task action has Stop specified.

Why doesn't my App Context work ?

First, we need to find out which method Tasker is using to detect app changes on your device.

Disable Menu / Prefs / UI / Beginner Mode then look in Menu / Prefs / Monitor to see if you have an entry App Check Method. If you don't have such an entry, Tasker is using its Accessibility Service.

If Tasker is using Usage Stats for app detection, you need to ask Android to give Tasker permission to do that, see Menu / More / Android Settings / App Usage Stats. Otherwise, you need to make sure Tasker's Accessibility Service is enabled in Android Settings, see Menu / More / Android Settings / Accessibility service.

Further tips:

if Tasker offers you the choice to use different methods, try the other methods. Remember to give Tasker permission in Android settings for the new method (see above).
If you are using Nova Launcher, set Settings / App & Widget Drawer / Advanced / Automatically Close to off.
Some apps (very few) aren't detected by Tasker, usually due to their internal structure.
Some custom Android ROMs also have special configurations which prevent Tasker's app detection working.

For the latter problem, there are a few things you can try:

look for special settings in your ROM that relate to 'keeping the launcher in memory'. They should be disabled.
change the build properties file. Look in /system/build.prop (or possibly /system/local.prop or /data/local.prop) for a line like:
ro.HOME_APP_ADJ=-17

Change it in a terminal program to look like this:

ro.HOME_APP_ADJ=1

If you didn't find an existing line, just add the new line as above.

Note: you will first need to make /system writeable. You can do that e.g. with Tasker's Remount action. Remember to make it not-writeable again after making the change.
try detecting apps with a state using the %WIN (window title) variable; create a new state
Variable Value, %WIN, Matches, TITLE
where TITLE is the title of the window of the app you are interested in. For this solution to work, you also need to enable Tasker's Accessibility Service in Android Settings.
You can check what %WIN shows for the app you are interested in with this profile:
Event: Variable Set, %WIN
Alert / Flash, Win is now %WIN

Why doesn't the Keyguard action work properly ?

Android does not officially support toggling of the Keyguard by an app. The Keyguard action was introduced in an early version of Tasker when a reliable workaround was possible.

In more recent Android versions, the workaround is no longer so reliable due to internal changes made within Android. If Keyguard works at all, there may be disturbing side-effects.

The Keyguard action will likely be most reliablewhen the display is on and and the Keyguard is already unlocked.

Some people have more luck with the same functionality provided by the Secure Settings plugin. After install, you can find the Secure Settings plugin in the Plugin action category. Note that a rooted device is not needed to use this part of Secure Settings.

Why doesn't Tasker think my device is rooted ?

Tasker requires two things before root functionality is enabled:

the su program must be in your path
one of the following must be found:
- a superuser package
- the word modversion somewhere in the file /system/build.prop

If root is not being detected on your device but you are sure that root can be used by Tasker, you can therefore probably fix that by adding a line like:

# modversion this line enables Tasker root support

to the top of the file /system/build.prop.

Why doesn't Tasker show my Local Media images anymore ?

When you select a Local Media image, Android grants Tasker rights to keep using it.

However, when you uninstall Tasker, Android forgets those rights and doesn't reassign them when you install Tasker again. This is clearly a failing in Android... On some devices Android also forgets the rights when the device is rebooted, but this is very rare and almost certainly a problem with the particular device involved.

To fix the problem, you wil unfortunately need to reselect the Local Media images in the Tasker UI so that Android grants it access rights again.

FAQ: Usage Problems

Why don't Tasker or its plugins work in the background on my device?