“WebM is an open, royalty-free, media file format designed for the web.” Or at-least, that’s what Google intended it to be.
You’ve probably never heard of WebM files, but it is an open alternative to MP4, a digital container for video and audio streams. MP4 files generally use the H.264 video codec, while WebM uses VP8 and VP9, also developed by Google. WebM never caught on like how MP4 did, despite it’s open format.
Apple devices are notorious for their lack of WebM support, and there is a bit of a back-story on this. Google Chrome used to utilize the Apple-developed WebKit engine, which Google abandoned in favor of their own rendering engine, Blink. Some have speculated that this is a major factor in why Apple never adopted WebM, but it makes watching WebM files on iPhones very difficult.
I wrote a simple app in nodejs that uses the Telegram Bot API to automatically convert these WebM files into the mp4 format. It polls telegram for new messages, checks if the message contains a WebM, and then launches a ffmpeg process to convert the file before uploading it back to the chat.