I made the sample to show that the HTML media tag works as expected and as long as the videos/audios are supported they would play. Some of the formats aren't supported by the OS, e.g. 3gp on iOS, so they would not play.
If you do not get the video or audio playing using a properly declared media tag, then there is a problem with the format under the current operating system and you would need to convert it to a supported format - one listed both in the Android and iOS supported media formats.
As previously mentioned, note that not only the file format is important but also the quality, encoding. resolution, etc. of the media files. Make sure that you cover the specific requirements listed in the two links I initially posted.
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