There's another scenario with MP3 files. MP3s need to selectively add padding bytes to their frames to ensure the final file size matches its stated bitrate. If an MP3 file's frames aren't properly padded with these bytes, it can still play normally, but its actual bitrate will be lower than what's claimed. Due to browsers calculating data positions at specific times based on MP3 file bitrates, this can lead to some inaccuracies.