diff --git a/AdjustIO.podspec b/AdjustIO.podspec
index 957351d91..92b755434 100644
--- a/AdjustIO.podspec
+++ b/AdjustIO.podspec
@@ -1,11 +1,11 @@
 Pod::Spec.new do |s|
   s.name         = "AdjustIO"
-  s.version      = "2.1.4"
+  s.version      = "2.2.0"
   s.summary      = "This is the iOS SDK of AdjustIo. You can read more about it at http://adjust.io."
   s.homepage     = "http://adjust.io"
   s.license      = { :type => 'MIT', :file => 'MIT-LICENSE' }
   s.author       = { "Christian Wellenbrock" => "welle@adeven.com" }
-  s.source       = { :git => "https://github.com/adeven/adjust_ios_sdk.git", :tag => "v2.1.4" }
+  s.source       = { :git => "https://github.com/adeven/adjust_ios_sdk.git", :tag => "v2.2.0" }
   s.platform     = :ios, '4.3'
   s.framework    = 'AdSupport', 'SystemConfiguration'
   s.source_files = 'AdjustIo/*.{h,m}', 'AdjustIo/AIAdditions/*.{h,m}'
diff --git a/AdjustIo/AIActivityHandler.m b/AdjustIo/AIActivityHandler.m
index 0701a2726..f36a4451e 100644
--- a/AdjustIo/AIActivityHandler.m
+++ b/AdjustIo/AIActivityHandler.m
@@ -283,11 +283,11 @@ - (BOOL)updateActivityState {
 
 - (void)readActivityState {
     @try {
-        NSString *filename = [self activityStateFilename];
+        NSString *filename = self.activityStateFilename;
         id object = [NSKeyedUnarchiver unarchiveObjectWithFile:filename];
         if ([object isKindOfClass:[AIActivityState class]]) {
             self.activityState = object;
-            [AILogger debug:@"Read activity state: %@", self.activityState];
+            [AILogger debug:@"Read activity state:  %@ uuid:%@", self.activityState, self.activityState.uuid];
             return;
         } else if (object == nil) {
             [AILogger verbose:@"Activity state file not found"];
@@ -303,7 +303,7 @@ - (void)readActivityState {
 }
 
 - (void)writeActivityState {
-    NSString *filename = [self activityStateFilename];
+    NSString *filename = self.activityStateFilename;
     BOOL result = [NSKeyedArchiver archiveRootObject:self.activityState toFile:filename];
     if (result == YES) {
         [AIUtil excludeFromBackup:filename];
diff --git a/AdjustIo/AIActivityState.h b/AdjustIo/AIActivityState.h
index a878e52e6..717a471e3 100644
--- a/AdjustIo/AIActivityState.h
+++ b/AdjustIo/AIActivityState.h
@@ -10,6 +10,9 @@
 
 @interface AIActivityState : NSObject <NSCoding>
 
+// persistent data
+@property (nonatomic, copy) NSString *uuid;
+
 // global counters
 @property (nonatomic, assign) int eventCount;
 @property (nonatomic, assign) int sessionCount;
@@ -19,8 +22,9 @@
 @property (nonatomic, assign) double sessionLength; // all durations in seconds
 @property (nonatomic, assign) double timeSpent;
 @property (nonatomic, assign) double lastActivity;  // all times in seconds since 1970
-
 @property (nonatomic, assign) double createdAt;
+
+// not persisted, only injected
 @property (nonatomic, assign) double lastInterval;
 
 - (void)resetSessionAttributes:(double)now;
diff --git a/AdjustIo/AIActivityState.m b/AdjustIo/AIActivityState.m
index 528f7a149..29006dd92 100644
--- a/AdjustIo/AIActivityState.m
+++ b/AdjustIo/AIActivityState.m
@@ -8,6 +8,7 @@
 
 #import "AIActivityState.h"
 #import "AIPackageBuilder.h"
+#import "UIDevice+AIAdditions.h"
 
 
 #pragma mark public implementation
@@ -17,6 +18,9 @@ - (id)init {
     self = [super init];
     if (self == nil) return nil;
 
+    // create UUID for new devices
+    self.uuid = [UIDevice.currentDevice aiCreateUuid];
+
     self.eventCount      = 0;
     self.sessionCount    = 0;
     self.subsessionCount = -1; // -1 means unknown
@@ -67,6 +71,12 @@ - (id)initWithCoder:(NSCoder *)decoder {
     self.timeSpent       = [decoder decodeDoubleForKey:@"timeSpent"];
     self.createdAt       = [decoder decodeDoubleForKey:@"createdAt"];
     self.lastActivity    = [decoder decodeDoubleForKey:@"lastActivity"];
+    self.uuid            = [decoder decodeObjectForKey:@"uuid"];
+
+    // create UUID for migrating devices
+    if (self.uuid == nil) {
+        self.uuid = [UIDevice.currentDevice aiCreateUuid];
+    }
 
     self.lastInterval = -1;
 
@@ -81,6 +91,7 @@ - (void)encodeWithCoder:(NSCoder *)encoder {
     [encoder encodeDouble:self.timeSpent     forKey:@"timeSpent"];
     [encoder encodeDouble:self.createdAt     forKey:@"createdAt"];
     [encoder encodeDouble:self.lastActivity  forKey:@"lastActivity"];
+    [encoder encodeObject:self.uuid          forKey:@"uuid"];
 }
 
 
@@ -92,6 +103,7 @@ - (void)injectGeneralAttributes:(AIPackageBuilder *)builder {
     builder.sessionLength   = self.sessionLength;
     builder.timeSpent       = self.timeSpent;
     builder.createdAt       = self.createdAt;
+    builder.uuid            = self.uuid;
 }
 
 @end
diff --git a/AdjustIo/AIAdditions/NSString+AIAdditions.h b/AdjustIo/AIAdditions/NSString+AIAdditions.h
index af09d2c7a..846af17bd 100644
--- a/AdjustIo/AIAdditions/NSString+AIAdditions.h
+++ b/AdjustIo/AIAdditions/NSString+AIAdditions.h
@@ -16,4 +16,6 @@
 - (NSString *)aiUrlEncode;
 - (NSString *)aiRemoveColons;
 
++ (NSString *)aiJoin:(NSString *)strings, ...;
+
 @end
diff --git a/AdjustIo/AIAdditions/NSString+AIAdditions.m b/AdjustIo/AIAdditions/NSString+AIAdditions.m
index 9318ae9db..43442d044 100644
--- a/AdjustIo/AIAdditions/NSString+AIAdditions.m
+++ b/AdjustIo/AIAdditions/NSString+AIAdditions.m
@@ -54,4 +54,18 @@ - (NSString *)aiRemoveColons {
     return [self stringByReplacingOccurrencesOfString:@":" withString:@""];
 }
 
++ (NSString *)aiJoin:(NSString *)first, ... {
+    NSString *iter, *result = first;
+    va_list strings;
+    va_start(strings, first);
+
+    while ((iter = va_arg(strings, NSString*))) {
+        NSString *capitalized = iter.capitalizedString;
+        result = [result stringByAppendingString:capitalized];
+    }
+
+    va_end(strings);
+    return result;
+}
+
 @end
diff --git a/AdjustIo/AIAdditions/UIDevice+AIAdditions.h b/AdjustIo/AIAdditions/UIDevice+AIAdditions.h
index f928cb894..62707848a 100644
--- a/AdjustIo/AIAdditions/UIDevice+AIAdditions.h
+++ b/AdjustIo/AIAdditions/UIDevice+AIAdditions.h
@@ -16,5 +16,6 @@
 - (NSString *)aiMacAddress;
 - (NSString *)aiDeviceType;
 - (NSString *)aiDeviceName;
+- (NSString *)aiCreateUuid;
 
 @end
diff --git a/AdjustIo/AIAdditions/UIDevice+AIAdditions.m b/AdjustIo/AIAdditions/UIDevice+AIAdditions.m
index f1770f371..82d7a384b 100644
--- a/AdjustIo/AIAdditions/UIDevice+AIAdditions.m
+++ b/AdjustIo/AIAdditions/UIDevice+AIAdditions.m
@@ -9,26 +9,74 @@
 #import "UIDevice+AIAdditions.h"
 #import "NSString+AIAdditions.h"
 
-#import <AdSupport/ASIdentifierManager.h>
 #import <sys/socket.h>
 #import <sys/sysctl.h>
 #import <net/if.h>
 #import <net/if_dl.h>
 
+#if !ADJUST_NO_IDFA
+#import <AdSupport/ASIdentifierManager.h>
+#endif
+
 @implementation UIDevice(AIAdditions)
 
 - (BOOL)aiTrackingEnabled {
-    if (NSClassFromString(@"ASIdentifierManager")) {
-        return ASIdentifierManager.sharedManager.advertisingTrackingEnabled;
-    } else {
+#if !ADJUST_NO_IDFA
+    NSString *className  = [NSString aiJoin:@"A", @"S", @"identifier", @"manager", nil];
+    NSString *keyManager = [NSString aiJoin:@"shared", @"manager", nil];
+    NSString *keyEnabled = [NSString aiJoin:@"is", @"advertising", @"tracking", @"enabled", nil];
+
+    Class class = NSClassFromString(className);
+    if (class) {
+        @try {
+            SEL selManager = NSSelectorFromString(keyManager);
+            SEL selEnabled = NSSelectorFromString(keyEnabled);
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
+            id manager   = [class performSelector:selManager];
+            BOOL enabled = (BOOL)[manager performSelector:selEnabled];
+#pragma clang diagnostic pop
+
+            return enabled;
+        } @catch (NSException *e) {
+            return NO;
+        }
+    } else
+#endif
+    {
         return NO;
     }
 }
 
 - (NSString *)aiIdForAdvertisers {
-    if (NSClassFromString(@"ASIdentifierManager")) {
-        return ASIdentifierManager.sharedManager.advertisingIdentifier.UUIDString;
-    } else {
+#if !ADJUST_NO_IDFA
+    NSString *className     = [NSString aiJoin:@"A", @"S", @"identifier", @"manager", nil];
+    NSString *keyManager    = [NSString aiJoin:@"shared", @"manager", nil];
+    NSString *keyIdentifier = [NSString aiJoin:@"advertising", @"identifier", nil];
+    NSString *keyString     = [NSString aiJoin:@"UUID", @"string", nil];
+
+    Class class = NSClassFromString(className);
+    if (class) {
+        @try {
+            SEL selManager    = NSSelectorFromString(keyManager);
+            SEL selIdentifier = NSSelectorFromString(keyIdentifier);
+            SEL selString     = NSSelectorFromString(keyString);
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
+            id manager       = [class performSelector:selManager];
+            id identifier    = [manager performSelector:selIdentifier];
+            NSString *string = [identifier performSelector:selString];
+#pragma clang diagnostic pop
+
+            return string;
+        } @catch (NSException *e) {
+            return @"";
+        }
+    } else
+#endif
+    {
         return @"";
     }
 }
@@ -101,4 +149,13 @@ - (NSString *)aiDeviceName {
     return machine;
 }
 
+- (NSString *)aiCreateUuid {
+    CFUUIDRef newUniqueId = CFUUIDCreate(kCFAllocatorDefault);
+    CFStringRef stringRef = CFUUIDCreateString(kCFAllocatorDefault, newUniqueId);
+    NSString *uuidString = (__bridge_transfer NSString*)stringRef;
+    NSString *lowerUuid = [uuidString lowercaseString];
+    CFRelease(newUniqueId);
+    return lowerUuid;
+}
+
 @end
diff --git a/AdjustIo/AIPackageBuilder.h b/AdjustIo/AIPackageBuilder.h
index 2aaeead3c..5af618f57 100644
--- a/AdjustIo/AIPackageBuilder.h
+++ b/AdjustIo/AIPackageBuilder.h
@@ -19,6 +19,7 @@
 @property (nonatomic, copy) NSString *environment;
 @property (nonatomic, copy) NSString *userAgent;
 @property (nonatomic, copy) NSString *clientSdk;
+@property (nonatomic, copy) NSString *uuid;
 @property (nonatomic, assign) BOOL trackingEnabled;
 
 // sessions
diff --git a/AdjustIo/AIPackageBuilder.m b/AdjustIo/AIPackageBuilder.m
index a8c5d44b6..e2ec18943 100644
--- a/AdjustIo/AIPackageBuilder.m
+++ b/AdjustIo/AIPackageBuilder.m
@@ -72,6 +72,7 @@ - (NSMutableDictionary *)defaultParameters {
     [self parameters:parameters setString:self.appToken         forKey:@"app_token"];
     [self parameters:parameters setString:self.macSha1          forKey:@"mac_sha1"];
     [self parameters:parameters setString:self.macShortMd5      forKey:@"mac_md5"];
+    [self parameters:parameters setString:self.uuid             forKey:@"ios_uuid"];
     [self parameters:parameters setString:self.idForAdvertisers forKey:@"idfa"];
     [self parameters:parameters setString:self.fbAttributionId  forKey:@"fb_id"];
     [self parameters:parameters setString:self.environment      forKey:@"environment"];
diff --git a/AdjustIo/AIPackageHandler.m b/AdjustIo/AIPackageHandler.m
index eddb05c88..23539898a 100644
--- a/AdjustIo/AIPackageHandler.m
+++ b/AdjustIo/AIPackageHandler.m
@@ -123,7 +123,7 @@ - (void)sendNextInternal {
 #pragma mark - private
 - (void)readPackageQueue {
     @try {
-        NSString *filename = [self packageQueueFilename];
+        NSString *filename = self.packageQueueFilename;
         id object = [NSKeyedUnarchiver unarchiveObjectWithFile:filename];
         if ([object isKindOfClass:[NSArray class]]) {
             self.packageQueue = object;
@@ -143,7 +143,7 @@ - (void)readPackageQueue {
 }
 
 - (void)writePackageQueue {
-    NSString *filename = [self packageQueueFilename];
+    NSString *filename = self.packageQueueFilename;
     BOOL result = [NSKeyedArchiver archiveRootObject:self.packageQueue toFile:filename];
     if (result == YES) {
         [AIUtil excludeFromBackup:filename];
diff --git a/AdjustIo/AIUtil.m b/AdjustIo/AIUtil.m
index 34e8451e9..95817d46e 100644
--- a/AdjustIo/AIUtil.m
+++ b/AdjustIo/AIUtil.m
@@ -13,7 +13,7 @@
 #include <sys/xattr.h>
 
 static NSString * const kBaseUrl   = @"https://app.adjust.io";
-static NSString * const kClientSdk = @"ios2.1.4";
+static NSString * const kClientSdk = @"ios2.2.0";
 
 
 #pragma mark -
diff --git a/README.md b/README.md
index 7f2ded24c..c39fcc43b 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ If you're using [CocoaPods][cocoapods], you can add the following line to your
 `Podfile` and continue with [step 3](#step3):
 
 ```ruby
-pod 'AdjustIO', :git => 'git://github.com/adeven/adjust_ios_sdk.git', :tag => 'v2.1.4'
+pod 'AdjustIO', :git => 'git://github.com/adeven/adjust_ios_sdk.git', :tag => 'v2.2.0'
 ```
 
 ### 1. Get the SDK
diff --git a/VERSION b/VERSION
index 7d2ed7c70..ccbccc3dc 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.1.4
+2.2.0
diff --git a/doc/idfa.md b/doc/idfa.md
new file mode 100644
index 000000000..612639465
--- /dev/null
+++ b/doc/idfa.md
@@ -0,0 +1,44 @@
+## Remove IDFA support
+
+If your app got rejected by Apple because your app is using the advertising
+identifier, this document is for you.
+
+1. Contact us at [support@adjust.io](mailto:support@adjust.io). We would like
+   to make sure that you are aware of the consequences of removing IDFA
+   support.
+
+2. After you talked with us, or when you just can't wait any longer, proceed
+   with the following steps to remove the IDFA support.
+
+### Remove the AdSupport framework
+
+- In the Project Navigator select your project. Make sure your target is
+  selected in the top left corner of the right hand window.
+
+- Select the `Build Phases` tab and expand the group `Link Binary with
+  Libraries`.
+
+- Select the `AdSupport.framework` and press the `-` button to remove it.
+
+- In the Project Navigator, expand the group `Frameworks`.
+
+- If the `AdSupport.framework` is in there, right click it, select `Delete` and
+  confirm `Remove Reference`.
+
+### Add the compiler flag `ADJUST_NO_IDFA`
+
+- In the Project Navigator select your project. Make sure your target is
+  selected in the top left corner of the right hand window.
+
+- Select the `Build Settings` tab and search for `Other C Flags` in the search
+  field below.
+
+- Double click on the right side of the `Other C Flags` line to change its
+  value
+
+- Press on the `+` button at the bottom of the overlay and paste the following
+  text into the selected line:
+
+    ```
+    -DADJUST_NO_IDFA
+    ```
diff --git a/doc/migration.md b/doc/migration.md
index 8d908635f..3d0be2d39 100644
--- a/doc/migration.md
+++ b/doc/migration.md
@@ -1,7 +1,7 @@
-## Migrate your AdjustIo SDK for iOS from v1.x to v2.1.4
+## Migrate your AdjustIo SDK for iOS from v1.x to v2.2.0
 
 1. Delete the old `AdjustIo` source folder from your Xcode project. Download
-   version v2.1.4 and drag the new folder into your Xcode project.
+   version v2.2.0 and drag the new folder into your Xcode project.
 
     ![][drag]
 
@@ -55,7 +55,7 @@
 2. The `appDidLaunch` method now expects your App Token instead of your App ID.
    You can find your App Token in your [dashboard].
 
-2. The AdjustIo SDK for iOS 2.1.4 uses [ARC][arc]. If you haven't done already,
+2. The AdjustIo SDK for iOS 2.2.0 uses [ARC][arc]. If you haven't done already,
    we recommend [transitioning your project to use ARC][transition] as well. If
    you don't want to use ARC, you have to enable ARC for all files of the
    AdjustIo SDK. Please consult the [README] for details.