diff --git a/SDWebImage/Core/SDImageCache.h b/SDWebImage/Core/SDImageCache.h
index 688d3fc2..1b1afd47 100644
--- a/SDWebImage/Core/SDImageCache.h
+++ b/SDWebImage/Core/SDImageCache.h
@@ -162,6 +162,7 @@ typedef NS_OPTIONS(NSUInteger, SDImageCacheOptions) {
  * @param key             The unique image cache key, usually it's image absolute URL
  * @param toDisk          Store the image to disk cache if YES. If NO, the completion block is called synchronously
  * @param completionBlock A block executed after the operation is finished
+ * @note If no image data is provided and encode to disk, we will try to detect the image format (using either `sd_imageFormat` or `SDAnimatedImage` protocol method) and animation status, to choose the best matched format, including GIF, JPEG or PNG.
  */
 - (void)storeImage:(nullable UIImage *)image
             forKey:(nullable NSString *)key
@@ -178,6 +179,7 @@ typedef NS_OPTIONS(NSUInteger, SDImageCacheOptions) {
  * @param key             The unique image cache key, usually it's image absolute URL
  * @param toDisk          Store the image to disk cache if YES. If NO, the completion block is called synchronously
  * @param completionBlock A block executed after the operation is finished
+ * @note If no image data is provided and encode to disk, we will try to detect the image format (using either `sd_imageFormat` or `SDAnimatedImage` protocol method) and animation status, to choose the best matched format, including GIF, JPEG or PNG.
  */
 - (void)storeImage:(nullable UIImage *)image
          imageData:(nullable NSData *)imageData
diff --git a/SDWebImage/Core/SDImageCache.m b/SDWebImage/Core/SDImageCache.m
index 06bc49a5..17403997 100644
--- a/SDWebImage/Core/SDImageCache.m
+++ b/SDWebImage/Core/SDImageCache.m
@@ -195,11 +195,16 @@
                     // Check image's associated image format, may return .undefined
                     SDImageFormat format = image.sd_imageFormat;
                     if (format == SDImageFormatUndefined) {
-                        // If we do not have any data to detect image format, check whether it contains alpha channel to use PNG or JPEG format
-                        if ([SDImageCoderHelper CGImageContainsAlpha:image.CGImage]) {
-                            format = SDImageFormatPNG;
+                        // If image is animated, use GIF (APNG may be better, but has bugs before macOS 10.14)
+                        if (image.sd_isAnimated) {
+                            format = SDImageFormatGIF;
                         } else {
-                            format = SDImageFormatJPEG;
+                            // If we do not have any data to detect image format, check whether it contains alpha channel to use PNG or JPEG format
+                            if ([SDImageCoderHelper CGImageContainsAlpha:image.CGImage]) {
+                                format = SDImageFormatPNG;
+                            } else {
+                                format = SDImageFormatJPEG;
+                            }
                         }
                     }
                     data = [[SDImageCodersManager sharedManager] encodedDataWithImage:image format:format options:nil];