opus

Two Opus files: a 1 second clip of 2.3 KB and a 5 second clip of 11 KB, both a 440 Hz tone at 16 kbps. Opus is the modern codec behind voice calls, WhatsApp voice notes and Discord, and it gives excellent quality at tiny sizes. Here it sits in a bare .opus file, which many upload forms and media libraries still do not list as allowed. Test whether yours recognises the extension, how it reports the MIME type and duration, and whether it can convert Opus to MP3 or WAV. The files are almost the same size as the OGG ones because the codec is the same.