diff --git a/app_main/build.gradle b/app_main/build.gradle
index 6cc0a466..89815cf1 100644
--- a/app_main/build.gradle
+++ b/app_main/build.gradle
@@ -5,7 +5,7 @@ android {
     buildToolsVersion "29.0.2"
     defaultConfig {
         applicationId "com.rfidresearchgroup.rfidtools"
-        minSdkVersion 24
+        minSdkVersion 21
         targetSdkVersion 28
         testInstrumentationRunner 'androidx.test.runner.AndroidJUnitRunner'
         versionCode 25