Free Online OGA to OGG Converter

OGA is an audio extension for OGG file and it was developed by Xiph.Org Foundation. OGG is an open container format designed for streaming and may contain independent video, text and audio files. To open OGA, you need either to install an appropriate software like Vorbis, or to convert the file to a more common format.

This format is free, which apparently is one of the reasons for its popularity. The used codecs supports variable bit rates (as a default), and .ogg files usually play back easily on all platforms. All things being equal, the sound quality exceeds that of mp3 somewhat.