diff --git a/app/dl_formats.py b/app/dl_formats.py
index 961ca1c9..51bfc67e 100644
--- a/app/dl_formats.py
+++ b/app/dl_formats.py
@@ -2,6 +2,7 @@
 
 AUDIO_FORMATS = ("m4a", "mp3", "opus", "wav")
 
+
 def get_format(format: str, quality: str) -> str:
     """
     Returns format for download
@@ -37,7 +38,13 @@ def get_format(format: str, quality: str) -> str:
         vres = f"[height<={quality}]" if quality != "best" else ""
         vcombo = vres + vfmt
 
-        return f"bestvideo{vcombo}+bestaudio{afmt}/best{vcombo}"
+        # iOS has strict requirements for video files, requiring h264 or h265
+        # video codec and aac audio codec in MP4 container. This format string
+        # attempts to get the fully compatible formats first, then the h264/h265
+        # video codec with any M4A audio codec (because audio is faster to
+        # convert if needed), and falls back to getting the best available MP4
+        # file.
+        return f"bestvideo[vcodec~='^((he|a)vc|h26[45])']{vres}+bestaudio[acodec=aac]/bestvideo[vcodec~='^((he|a)vc|h26[45])']{vres}+bestaudio{afmt}/bestvideo{vcombo}+bestaudio{afmt}/best{vcombo}"
 
     raise Exception(f"Unkown format {format}")
 
@@ -55,29 +62,41 @@ def get_opts(format: str, quality: str, ytdl_opts: dict) -> dict:
     Returns:
       ytdl_opts: Extra options
     """
-    
+
     opts = copy.deepcopy(ytdl_opts)
 
     postprocessors = []
 
     if format in AUDIO_FORMATS:
-        postprocessors.append({
-            "key": "FFmpegExtractAudio",
-            "preferredcodec": format,
-            "preferredquality": 0 if quality == "best" else quality,
-        })
-
-        #Audio formats without thumbnail
+        postprocessors.append(
+            {
+                "key": "FFmpegExtractAudio",
+                "preferredcodec": format,
+                "preferredquality": 0 if quality == "best" else quality,
+            }
+        )
+
+        # Audio formats without thumbnail
         if format not in ("wav") and "writethumbnail" not in opts:
             opts["writethumbnail"] = True
-            postprocessors.append({"key": "FFmpegThumbnailsConvertor", "format": "jpg", "when": "before_dl"})
+            postprocessors.append(
+                {
+                    "key": "FFmpegThumbnailsConvertor",
+                    "format": "jpg",
+                    "when": "before_dl",
+                }
+            )
             postprocessors.append({"key": "FFmpegMetadata"})
             postprocessors.append({"key": "EmbedThumbnail"})
-    
+
     if format == "thumbnail":
         opts["skip_download"] = True
         opts["writethumbnail"] = True
-        postprocessors.append({"key": "FFmpegThumbnailsConvertor", "format": "jpg", "when": "before_dl"})
-    
-    opts["postprocessors"] = postprocessors + (opts["postprocessors"] if "postprocessors" in opts else [])
+        postprocessors.append(
+            {"key": "FFmpegThumbnailsConvertor", "format": "jpg", "when": "before_dl"}
+        )
+
+    opts["postprocessors"] = postprocessors + (
+        opts["postprocessors"] if "postprocessors" in opts else []
+    )
     return opts