Convert MP3 to OPUS Online
Shrink your audio files by 50% while keeping the same quality. Free, in your browser.
.mp3 · up to 100 MB
What it's for
MP3 to OPUS: modern audio at half the size
50% less storage
Opus at 64 kbps matches MP3 at 128 kbps quality. Halve your audio library size without losing quality.
Optimized for Discord and bots
Discord's native format. Ideal for server sounds, music bots, and Discord Nitro sound clips.
100% private
Your audio files are never uploaded to any server. Local conversion with FFmpeg.wasm.
IETF open standard
Opus (RFC 6716) is the most modern and efficient audio codec ratified by an international standards body.
How it works
Three steps, no hassle
Upload your MP3 file
Drag or select your .mp3 file. Up to 50 MB, no signup.
Conversion to Opus
FFmpeg.wasm decodes the MP3 and re-encodes to Opus in an OGG container directly in your browser. No server uploads.
Download your OGG/OPUS file
Download the resulting .opus file — up to 50% smaller with quality equivalent to the original.
FAQ
Got questions?
Opus outperforms MP3 on nearly every objective and subjective metric. Technically, Opus uses MDCT transforms with adaptive window sizes (2.5 ms to 20 ms depending on content) versus MP3's fixed windows, eliminating the pre-echo artifacts on transients that are MP3's most audible flaw at medium bitrates. Opus implements state-of-the-art perceptual noise shaping based on CELT/Vorbis research. In blind listening tests published by Xiph.org in 2012 and confirmed by subsequent independent studies, Opus at 64 kbps matches MP3 at 128 kbps quality, and Opus at 96 kbps is perceptually indistinguishable from the source for virtually any audio content. The difference is especially marked for voice (where Opus at 32 kbps surpasses MP3 at 128 kbps) and high-frequency content where MP3 loses definition. MP3 was standardized in 1993 with the perceptual compression technology available at the time; Opus incorporates 20 additional years of audio coding research.
In practical terms, an MP3 at 128 kbps can be converted to Opus at 64 kbps with perceptually equivalent quality, resulting in a file 50% smaller. A 10 MB MP3 at 128 kbps becomes approximately a 5 MB Opus file at 64 kbps with the same perceived quality. For voice content the difference is even greater: Opus at 24–32 kbps matches or exceeds MP3 at 96–128 kbps. For podcasts, audiobooks, and spoken content, the typical size reduction is 60–70% with no perceptible quality loss.
Discord uses Opus for all voice channels, video calls, and voice messages. Discord Nitro custom sounds (audio clips assignable to server events) are also stored in Opus format. If you are a Discord bot developer and need to play audio in a voice channel, the discord.js library with @discordjs/voice requires audio in Opus or PCM format; converting your MP3 files to Opus reduces the real-time processing needed and improves bot latency. Sound files for Discord music bots also benefit from Opus due to the lower bandwidth required for streaming.
Technically yes, but platform support is partial. Spotify supports Opus internally for adaptive streaming. Apple Podcasts supports AAC and MP3 but not Opus directly (though it transcodes internally). Podcast RSS feeds with Opus enclosures are supported by Pocket Casts, AntennaPod, Podcast Addict, and most modern Android clients, but not all iOS players. The practical recommendation is to distribute in MP3 for maximum compatibility and use Opus internally for storage and distribution to platforms that explicitly support it.
For voice: 24–32 kbps mono is transparent for calls and voice podcasts. For music: 96 kbps stereo is generally transparent for most listeners in blind tests. For high-quality archiving: 128 kbps stereo is the Xiph.org recommendation for quality practically indistinguishable from the source on any content. The key difference from MP3 is that at these bitrates Opus produces significantly better quality, so you don't need the 192–320 kbps that many MP3 users consider necessary.
Opus support has grown enormously since 2012. VLC (all platforms), Firefox, Chrome, Edge, Opera, native Android (since Android 5.0 Lollipop, 2014), foobar2000 with plugins, updated Winamp, and most Linux music clients play Opus without issues. Windows Media Player and Apple Music do not support Opus without additional plugins. On mobile, both Android and iOS third-party players like Poweramp, VLC, and Shuttle have supported Opus for years. For home use with modern players, Opus has broad support; for maximum universal compatibility including older devices, MP3 is still the safer choice.
Convert MP3 to OPUS: modern audio at half the bitrate
MP3 was designed at Fraunhofer IIS in the late 1980s and early 1990s, standardized as ISO/IEC 11172-3 in 1993, and released to the general public in 1995 when rock band Aerosmith distributed the first commercial track in MP3 format over the internet. At that time, the perceptual compression technology available could encode recognizable musical audio at 128 kbps on processors of the era. Three decades later, MP3 remains the most widespread audio format in the world thanks to that early mass adoption, but its encoding technology is fundamentally obsolete. Opus, standardized in RFC 6716 of September 2012, incorporates two additional decades of research in psychoacoustics, signal processing, and audio coding. The efficiency difference is dramatic: Opus at 64 kbps delivers quality equivalent to MP3 at 128 kbps, meaning the same audio content takes up half the space with the same perceived quality. The fact that MP3 patents expired in 2017 does not change its technical disadvantage versus Opus; it simply means both formats are now equally free to use, making Opus's technical superiority the only relevant criterion for new projects. For large-volume audio collections, for content distribution via streaming, or for optimizing storage on space-constrained devices, converting MP3 to Opus is the technically correct decision if the playback environment supports it. This includes VLC on all platforms, Firefox, Chrome, Edge, Android 5.0 and later, and most Linux music clients, covering the vast majority of modern software and devices. There is no limit on the number of files per session and no usage restrictions on any available function.
The most relevant use cases for MP3 to Opus conversion in 2025 are Discord bot development where the discord.js library with @discordjs/voice processes Opus natively eliminating real-time transcoding, audio distribution for WebRTC applications where browsers implement the Opus codec natively in the WebRTC and MediaRecorder APIs so using Opus avoids intermediate conversions, VoIP pipeline optimization where Asterisk, FreeSWITCH, and Kamailio support Opus natively since their 2014-2015 versions, storage of podcast and audiobook collections with 50-70 percent space reduction for voice content, and preparation of audio assets for web applications with lower load times and lower bandwidth consumption. The network latency reduction that Opus provides over MP3 is relevant in real-time applications: needing less data per unit of time for the same quality means smaller playback buffers and lower perceived latency. These improvements compound across large content libraries, where the 50 percent storage reduction from MP3 to Opus represents meaningful cost savings at scale and can be the difference between a sustainable hosting budget and prohibitive bandwidth costs. For all these scenarios, starting from MP3 and re-encoding to Opus at a lower bitrate produces equivalent-quality output at significantly smaller size. The tool is compatible with Chrome, Edge, Firefox, and Safari on desktop and mobile without any additional configuration. The resulting file follows IETF and Xiph.org open standards for maximum compatibility with audio players and software. The process is completely free and requires no signup or installation of additional software. All conversion occurs locally in the user's browser via FFmpeg.wasm, ensuring complete privacy.
Convertir.ai performs the MP3 to Opus conversion entirely in the browser with FFmpeg.wasm. The process decodes the MP3 stream with the libmpg123 decoder to 44.1 kHz or 48 kHz PCM, applies a resample to 48 kHz if the source stream is at a different frequency since Opus has 48 kHz as its native sample rate per RFC 6716, and re-encodes with libopus at the selected bitrate, defaulting to 64 kbps stereo for music with a 32 kbps mono option for voice. The output container is OGG with .opus extension, the standard format for Opus outside of WebM and Matroska containers. The process respects the channel structure and metadata of the source MP3: ID3v1 and ID3v2 tags including artist, album, title, track number, genre, comment, and embedded cover art are transferred to the OGG Opus container as Vorbis Comment tags, the standard metadata format for OGG. Files without tags are also converted correctly. The conversion is fully deterministic for the same input file and bitrate configuration, facilitating integrity verification in batch processing workflows for large audio libraries. No quantity limit, no signup, no watermark. All processing occurs in browser memory without any transfer to external servers, ensuring complete privacy for sensitive or copyright-protected audio content. There is no limit on the number of files per session and no usage restrictions on any available function. The tool is compatible with Chrome, Edge, Firefox, and Safari on desktop and mobile without any additional configuration. The resulting file follows IETF and Xiph.org open standards for maximum compatibility with audio players and software.