diff --git a/YoutubeParser/Classes/HCYoutubeParser.h b/YoutubeParser/Classes/HCYoutubeParser.h
index de84413..3be8b17 100644
--- a/YoutubeParser/Classes/HCYoutubeParser.h
+++ b/YoutubeParser/Classes/HCYoutubeParser.h
@@ -53,7 +53,7 @@ typedef enum {
  @param youtubeURL the the complete youtube video url, either youtu.be or youtube.com
  @return string with desired youtube id
  */
-+ (NSString *)youtubeIDFromYoutubeURL:(NSURL *)youtubeURL;
++ (nullable NSString *)youtubeIDFromYoutubeURL:(nullable NSURL *)youtubeURL;
 
 /**
  Method for retreiving a iOS supported video link
@@ -62,7 +62,7 @@ typedef enum {
  @return dictionary with the available formats for the selected video
  
  */
-+ (NSDictionary *)h264videosWithYoutubeURL:(NSURL *)youtubeURL;
++ (nullable NSDictionary *)h264videosWithYoutubeURL:(nullable NSURL *)youtubeURL;
 
 /**
  Method for retreiving an iOS supported video link
@@ -71,7 +71,7 @@ typedef enum {
  @return dictionary with the available formats for the selected video
  
  */
-+ (NSDictionary *)h264videosWithYoutubeID:(NSString *)youtubeID;
++ (nullable NSDictionary *)h264videosWithYoutubeID:(nullable NSString *)youtubeID;
 
 /**
  Block based method for retreiving a iOS supported video link
@@ -80,8 +80,8 @@ typedef enum {
  @param completeBlock the block which is called on completion
  
  */
-+ (void)h264videosWithYoutubeURL:(NSURL *)youtubeURL
-                   completeBlock:(void(^)(NSDictionary *videoDictionary, NSError *error))completeBlock;
++ (void)h264videosWithYoutubeURL:(nullable NSURL *)youtubeURL
+                   completeBlock:(nonnull void(^)( NSDictionary * _Nullable videoDictionary, NSError * _Nullable error))completeBlock;
 
 /**
  Method for retreiving a thumbnail url for wanted youtube id
@@ -89,7 +89,7 @@ typedef enum {
  @param youtubeURL the complete youtube video id
  @param thumbnailSize the wanted size of the thumbnail
  */
-+ (NSURL *)thumbnailUrlForYoutubeURL:(NSURL *)youtubeURL
++ (nullable NSURL *)thumbnailUrlForYoutubeURL:(nullable NSURL *)youtubeURL
                          thumbnailSize:(YouTubeThumbnail)thumbnailSize;
 
 /**
@@ -99,9 +99,9 @@ typedef enum {
  @param thumbnailSize the wanted size of the thumbnail
  @param completeBlock the block which is called on completion
  */
-+ (void)thumbnailForYoutubeURL:(NSURL *)youtubeURL
++ (void)thumbnailForYoutubeURL:(nullable NSURL *)youtubeURL
 				 thumbnailSize:(YouTubeThumbnail)thumbnailSize
-				 completeBlock:(void(^)(HCImage *image, NSError *error))completeBlock;
+				 completeBlock:(nonnull void(^)(HCImage * _Nullable image, NSError * _Nullable error))completeBlock;
 
 /**
  Method for retreiving a thumbnail for wanted youtube id
@@ -110,9 +110,9 @@ typedef enum {
  @param thumbnailSize the wanted size of the thumbnail
  @param completeBlock the block which is called on completion
  */
-+ (void)thumbnailForYoutubeID:(NSString *)youtubeID
++ (void)thumbnailForYoutubeID:(nullable NSString *)youtubeID
 				thumbnailSize:(YouTubeThumbnail)thumbnailSize
-				completeBlock:(void(^)(HCImage *image, NSError *error))completeBlock;
+				completeBlock:(nonnull void(^)(HCImage * _Nullable image, NSError * _Nullable error))completeBlock;
 
 
 /**
@@ -122,6 +122,6 @@ typedef enum {
  @param completeBlock the block which is called on completion
  
  */
-+ (void)detailsForYouTubeURL:(NSURL *)youtubeURL
-               completeBlock:(void(^)(NSDictionary *details, NSError *error))completeBlock;
++ (void)detailsForYouTubeURL:(nullable NSURL *)youtubeURL
+               completeBlock:(nonnull void(^)(NSDictionary * _Nullable details, NSError * _Nullable error))completeBlock;
 @end
diff --git a/YoutubeParser/Classes/HCYoutubeParser.m b/YoutubeParser/Classes/HCYoutubeParser.m
index 079e05b..c1e8bdb 100644
--- a/YoutubeParser/Classes/HCYoutubeParser.m
+++ b/YoutubeParser/Classes/HCYoutubeParser.m
@@ -198,7 +198,7 @@ + (NSDictionary *)h264videosWithYoutubeURL:(NSURL *)youtubeURL {
 }
 
 + (void)h264videosWithYoutubeURL:(NSURL *)youtubeURL
-                   completeBlock:(void(^)(NSDictionary *videoDictionary, NSError *error))completeBlock {
+                   completeBlock:(void(^)(NSDictionary * _Nullable videoDictionary, NSError * _Nullable error))completeBlock {
     NSString *youtubeID = [self youtubeIDFromYoutubeURL:youtubeURL];
     if (youtubeID) {
         dispatch_queue_t queue = dispatch_queue_create("me.hiddencode.yt.backgroundqueue", 0);