diff --git a/android/src/main/java/com/onesignal/rnonesignalandroid/RNOneSignal.java b/android/src/main/java/com/onesignal/rnonesignalandroid/RNOneSignal.java
index a9b093de..9967e2d7 100644
--- a/android/src/main/java/com/onesignal/rnonesignalandroid/RNOneSignal.java
+++ b/android/src/main/java/com/onesignal/rnonesignalandroid/RNOneSignal.java
@@ -598,6 +598,10 @@ public void addOutcomeWithValue(String name, double value) {
 
     @Override
     public void login(String externalUserId) {
+        if (externalUserId == null || externalUserId.isEmpty()) {
+            Logging.error("login called with a null or empty externalUserId", null);
+            return;
+        }
         OneSignal.login(externalUserId);
     }
 
diff --git a/ios/RCTOneSignal/RCTOneSignalEventEmitter.mm b/ios/RCTOneSignal/RCTOneSignalEventEmitter.mm
index 4273ac11..180c35eb 100644
--- a/ios/RCTOneSignal/RCTOneSignalEventEmitter.mm
+++ b/ios/RCTOneSignal/RCTOneSignalEventEmitter.mm
@@ -138,6 +138,11 @@ + (void)sendEventWithName:(NSString *)name withBody:(NSDictionary *)body {
 }
 
 RCT_EXPORT_METHOD(login : (NSString *)externalId) {
+  if (externalId == nil || [externalId length] == 0) {
+    [OneSignalLog onesignalLog:ONE_S_LL_ERROR
+                       message:@"login called with a nil or empty externalId"];
+    return;
+  }
   [OneSignal login:externalId];
 }
 
diff --git a/src/helpers.test.ts b/src/helpers.test.ts
index 8d904ebf..24b6f7ae 100644
--- a/src/helpers.test.ts
+++ b/src/helpers.test.ts
@@ -5,6 +5,7 @@ import { IOS_NULL_SENTINEL } from './constants/internal';
 import {
   encodeNullsForIOS,
   isNativeModuleLoaded,
+  isNonEmptyString,
   isObjectSerializable,
   isValidCallback,
 } from './helpers';
@@ -66,6 +67,23 @@ describe('helpers', () => {
     });
   });
 
+  describe('isNonEmptyString', () => {
+    test.each([
+      { description: 'a non-empty string', value: 'id', expected: true },
+      { description: 'a whitespace string', value: ' ', expected: true },
+      { description: 'an empty string', value: '', expected: false },
+      { description: 'null', value: null, expected: false },
+      { description: 'undefined', value: undefined, expected: false },
+      { description: 'a number', value: 1, expected: false },
+      { description: 'a boolean', value: true, expected: false },
+    ])(
+      'should return $expected for $description',
+      ({ value, expected }: { description: string; value: unknown; expected: boolean }) => {
+        expect(isNonEmptyString(value)).toBe(expected);
+      },
+    );
+  });
+
   describe('isObjectSerializable', () => {
     test.each([
       { description: 'an empty object', value: {} },
diff --git a/src/helpers.ts b/src/helpers.ts
index ca6e0f41..76d28927 100644
--- a/src/helpers.ts
+++ b/src/helpers.ts
@@ -18,6 +18,10 @@ export function isNativeModuleLoaded(module: object | null | undefined): boolean
   return true;
 }
 
+export function isNonEmptyString(value: unknown): value is string {
+  return typeof value === 'string' && value.length > 0;
+}
+
 /**
  * Returns true if the value is a JSON-serializable object.
  */
diff --git a/src/index.test.ts b/src/index.test.ts
index 99bc865f..eb8b1c48 100644
--- a/src/index.test.ts
+++ b/src/index.test.ts
@@ -112,6 +112,18 @@ describe('OneSignal', () => {
       expect(mockRNOneSignal.initialize).not.toHaveBeenCalled();
     });
 
+    test('should not initialize if appId is null', () => {
+      OneSignal.initialize(null as unknown as string);
+      expect(mockRNOneSignal.initialize).not.toHaveBeenCalled();
+      expect(errorSpy).toHaveBeenCalledWith('OneSignal: initialize: appId is required');
+    });
+
+    test('should not initialize if appId is empty', () => {
+      OneSignal.initialize('');
+      expect(mockRNOneSignal.initialize).not.toHaveBeenCalled();
+      expect(errorSpy).toHaveBeenCalledWith('OneSignal: initialize: appId is required');
+    });
+
     test('should keep a permission event that arrives before the startup read resolves', async () => {
       let resolveStartupRead: ((granted: boolean) => void) | undefined;
       vi.mocked(mockRNOneSignal.hasNotificationPermission).mockReturnValueOnce(
@@ -180,6 +192,18 @@ describe('OneSignal', () => {
       OneSignal.login('external-123');
       expect(mockRNOneSignal.login).not.toHaveBeenCalled();
     });
+
+    test('should not login if externalId is null', () => {
+      OneSignal.login(null as unknown as string);
+      expect(mockRNOneSignal.login).not.toHaveBeenCalled();
+      expect(errorSpy).toHaveBeenCalledWith('OneSignal: login: externalId is required');
+    });
+
+    test('should not login if externalId is empty', () => {
+      OneSignal.login('');
+      expect(mockRNOneSignal.login).not.toHaveBeenCalled();
+      expect(errorSpy).toHaveBeenCalledWith('OneSignal: login: externalId is required');
+    });
   });
 
   describe('logout', () => {
@@ -676,6 +700,16 @@ describe('OneSignal', () => {
         expect(mockRNOneSignal.setLanguage).toHaveBeenCalledWith('en');
       });
 
+      test('forwards an empty language so native can reset', () => {
+        OneSignal.User.setLanguage('');
+        expect(mockRNOneSignal.setLanguage).toHaveBeenCalledWith('');
+      });
+
+      test('does not set a null language', () => {
+        OneSignal.User.setLanguage(null as unknown as string);
+        expect(mockRNOneSignal.setLanguage).not.toHaveBeenCalled();
+      });
+
       test('should not set language if native module is not loaded', () => {
         isNativeLoadedSpy.mockReturnValue(false);
         OneSignal.User.setLanguage('en');
@@ -748,6 +782,18 @@ describe('OneSignal', () => {
         OneSignal.User.addEmail(EMAIL);
         expect(mockRNOneSignal.addEmail).not.toHaveBeenCalled();
       });
+
+      test('should not add email if email is null', () => {
+        OneSignal.User.addEmail(null as unknown as string);
+        expect(mockRNOneSignal.addEmail).not.toHaveBeenCalled();
+        expect(errorSpy).toHaveBeenCalledWith('OneSignal: addEmail: email is required');
+      });
+
+      test('should not add email if email is empty', () => {
+        OneSignal.User.addEmail('');
+        expect(mockRNOneSignal.addEmail).not.toHaveBeenCalled();
+        expect(errorSpy).toHaveBeenCalledWith('OneSignal: addEmail: email is required');
+      });
     });
 
     describe('removeEmail', () => {
@@ -1306,16 +1352,16 @@ describe('OneSignal', () => {
           expect(mockRNOneSignal.addTrigger).toHaveBeenCalledWith('key', 'value');
         });
 
-        test('should log error but still call native method if key is missing', () => {
+        test('should not add trigger if key is missing', () => {
           OneSignal.InAppMessages.addTrigger('', 'value');
           expect(errorSpy).toHaveBeenCalled();
-          expect(mockRNOneSignal.addTrigger).toHaveBeenCalledWith('', 'value');
+          expect(mockRNOneSignal.addTrigger).not.toHaveBeenCalled();
         });
 
-        test('should log error but still call native method if value is null', () => {
+        test('should not add trigger if value is null', () => {
           OneSignal.InAppMessages.addTrigger('key', null as unknown as string);
           expect(errorSpy).toHaveBeenCalled();
-          expect(mockRNOneSignal.addTrigger).toHaveBeenCalledWith('key', null);
+          expect(mockRNOneSignal.addTrigger).not.toHaveBeenCalled();
         });
 
         test('should not add trigger if native module is not loaded', () => {
diff --git a/src/index.ts b/src/index.ts
index 212299d1..371f9a94 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -18,6 +18,7 @@ import NotificationWillDisplayEvent from './events/NotificationWillDisplayEvent'
 import {
   encodeNullsForIOS,
   isNativeModuleLoaded,
+  isNonEmptyString,
   isObjectSerializable,
   isValidCallback,
 } from './helpers';
@@ -107,6 +108,10 @@ export namespace OneSignal {
   /** Initializes the OneSignal SDK. This should be called during startup of the application. */
   export function initialize(appId: string) {
     if (!isNativeModuleLoaded(RNOneSignal)) return;
+    if (!isNonEmptyString(appId)) {
+      console.error('OneSignal: initialize: appId is required');
+      return;
+    }
 
     RNOneSignal.initialize(appId);
 
@@ -121,6 +126,10 @@ export namespace OneSignal {
    */
   export function login(externalId: string) {
     if (!isNativeModuleLoaded(RNOneSignal)) return;
+    if (!isNonEmptyString(externalId)) {
+      console.error('OneSignal: login: externalId is required');
+      return;
+    }
 
     RNOneSignal.login(externalId);
   }
@@ -445,9 +454,13 @@ export namespace OneSignal {
       return RNOneSignal.getExternalId();
     }
 
-    /** Explicitly set a 2-character language code for the user. */
+    /** Explicitly set a 2-character language code for the user. Empty string resets to the device language. */
     export function setLanguage(language: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (typeof language !== 'string') {
+        console.error('OneSignal: setLanguage: language is required');
+        return;
+      }
 
       RNOneSignal.setLanguage(language);
     }
@@ -455,6 +468,10 @@ export namespace OneSignal {
     /** Set an alias for the current user. If this alias label already exists on this user, it will be overwritten with the new alias id. */
     export function addAlias(label: string, id: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(label) || !isNonEmptyString(id)) {
+        console.error('OneSignal: addAlias: must include a label and an id');
+        return;
+      }
 
       RNOneSignal.addAlias(label, id);
     }
@@ -469,6 +486,10 @@ export namespace OneSignal {
     /** Remove an alias from the current user. */
     export function removeAlias(label: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(label)) {
+        console.error('OneSignal: removeAlias: label is required');
+        return;
+      }
 
       RNOneSignal.removeAlias(label);
     }
@@ -483,6 +504,10 @@ export namespace OneSignal {
     /** Add a new email subscription to the current user. */
     export function addEmail(email: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(email)) {
+        console.error('OneSignal: addEmail: email is required');
+        return;
+      }
 
       RNOneSignal.addEmail(email);
     }
@@ -493,6 +518,10 @@ export namespace OneSignal {
      */
     export function removeEmail(email: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(email)) {
+        console.error('OneSignal: removeEmail: email is required');
+        return;
+      }
 
       RNOneSignal.removeEmail(email);
     }
@@ -500,6 +529,10 @@ export namespace OneSignal {
     /** Add a new SMS subscription to the current user. */
     export function addSms(smsNumber: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(smsNumber)) {
+        console.error('OneSignal: addSms: smsNumber is required');
+        return;
+      }
 
       RNOneSignal.addSms(smsNumber);
     }
@@ -510,6 +543,10 @@ export namespace OneSignal {
      */
     export function removeSms(smsNumber: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(smsNumber)) {
+        console.error('OneSignal: removeSms: smsNumber is required');
+        return;
+      }
 
       RNOneSignal.removeSms(smsNumber);
     }
@@ -521,7 +558,7 @@ export namespace OneSignal {
     export function addTag(key: string, value: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
 
-      if (!key || value === undefined || value === null) {
+      if (!isNonEmptyString(key) || value == null) {
         console.error('OneSignal: addTag: must include a key and a value');
         return;
       }
@@ -543,6 +580,10 @@ export namespace OneSignal {
     /** Remove the data tag with the provided key from the current user. */
     export function removeTag(key: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(key)) {
+        console.error('OneSignal: removeTag: key is required');
+        return;
+      }
 
       RNOneSignal.removeTag(key);
     }
@@ -787,9 +828,10 @@ export namespace OneSignal {
     export function addTrigger(key: string, value: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
 
-      // value can be assigned to `false` so we cannot just check `!value`
-      if (!key || value == null) {
+      // false is a valid trigger value, so reject only null/undefined for value.
+      if (!isNonEmptyString(key) || value == null) {
         console.error('OneSignal: addTrigger: must include a key and a value');
+        return;
       }
 
       RNOneSignal.addTrigger(key, value);
@@ -808,6 +850,10 @@ export namespace OneSignal {
     /** Remove the trigger with the provided key from the current user. */
     export function removeTrigger(key: string) {
       if (!isNativeModuleLoaded(RNOneSignal)) return;
+      if (!isNonEmptyString(key)) {
+        console.error('OneSignal: removeTrigger: key is required');
+        return;
+      }
 
       RNOneSignal.removeTrigger(key);
     }