SPX to OPUS Converter
Processing entirely on your device — large files may take a moment.
Speex Voice Audio and Opus Audio exist for different jobs: SPX is Speex voice audio in an Ogg container — the codec of old VoIP recorders and Asterisk phone systems. Opus delivers the smallest files with the best quality for streaming and messaging.
This converter runs entirely in your browser using WebAssembly — your files never leave your device, nothing is uploaded, and there are no watermarks, sign-ups or queues. Drop in several files at once to convert them as a batch.
How SPX compares to OPUS
| SPX | OPUS | |
|---|---|---|
| Compression | Lossy Speex (Ogg) | Lossy (6–510 kbps) |
| Quality | Narrowband/wideband speech | State of the art |
| Compatibility | Legacy VoIP stacks | Software strong, hardware lagging |
| Best for | Call recordings, phone systems | Calls, live streams, chat |
How to convert SPX to OPUS
- 1
Select your files
Drag & drop your SPX files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Convert to OPUS". The conversion runs entirely inside your browser using WebAssembly — no upload, no queue, no waiting.
- 3
Download results
Download each converted OPUS file individually, or grab everything at once as a ZIP archive.
About the SPX format
SPX is Speex speech audio in an Ogg container — the open voice codec of the 2000s VoIP wave, tuned for telephone-band speech at absurdly low bitrates. Asterisk PBX call recordings and old conferencing archives are where you meet it.
Speex was formally retired in favor of Opus, and players have followed. Converting SPX to MP3 (or Opus for the adventurous) rescues call archives before they become unplayable.
+ Strengths
- ✓Extremely compact for speech
- ✓Open-source lineage
! Limitations
- −Speech-only: music is unusable
- −Format officially retired
About the OPUS format
Opus (IETF RFC 6716, 2012) is the codec that ended the argument: it merges Skype's CELT and Xiph's SILK into one royalty-free format that is simultaneously the best low-latency speech codec and a superb music codec. WebRTC calls, Discord, WhatsApp, WhatsApp calls, YouTube's low-bitrate streams and Zoom all run on it.
At 6 kbps it keeps speech intelligible; at 128 kbps it is transparent for music; latency can dip below 5 ms for live conversation. Its weakness is hardware: dedicated chips and some car/hi-fi devices still lack it, and standalone .opus files are less recognized than MP3 on random devices.
+ Strengths
- ✓Best quality-per-bit across speech and music
- ✓Ultra-low latency — built for live calls
- ✓Royalty-free IETF standard
! Limitations
- −Hardware support still incomplete
- −Not a mastering or archival format
Why convert SPX to OPUS?
Think of it as moving your file to the container that fits the job. Speech-only: music is unusable OPUS works differently: Best quality-per-bit across speech and music If any of that sounds like your task, run the conversion — it takes seconds and nothing leaves your device.
Frequently asked questions
Is this SPX to OPUS converter really free?
Yes — completely free, with no sign-up, no watermark and no daily conversion limits. The site is supported by advertising.
Are my files uploaded to a server?
No. The conversion runs entirely inside your browser using WebAssembly, so your files never leave your device — that is what makes it instant and private.
Does it work on Windows, Mac, iPhone and Android?
Yes. Anything with a modern browser works: Windows, macOS, Linux, Android and iOS. No software installation is required.
Is there a file size limit for SPX to OPUS?
The only limit is your device's memory, since nothing is uploaded. Files up to a few hundred megabytes work fine on a modern desktop browser; very large files simply take a little longer.
Are tags like title and artist preserved?
Tag handling varies between target formats and this conversion focuses on the audio itself. For archival copies where tags matter, keep the original file; the converted copy is for playback and sharing.
Will converting SPX to OPUS reduce audio quality?
If OPUS is lossless, the output contains everything the SPX file contains — no further loss is added. If OPUS is lossy, one recompression pass is unavoidable; the quality slider controls how much. Loss that already happened in the source file can never be undone by converting.