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MP3 to Opus Converter

Turn MP3 files into Opus in a couple of clicks. MP3 is the universal lossy audio format; Opus is the best low-bitrate codec available — voice and music. Some detail is discarded to fit the target format; how much depends on the format and your settings.

Not uploaded to any serverConverted on this deviceGone when you close the tabHow this works

Drop your files here

MP3 files (.mp3) · up to 300 MB each

or paste files from your clipboard

Ready when you are

Drop a MP3 file above and FileTools360 will turn it into Opus — right here on your device, without uploading anything.

⌘K to search converters

How to use it

1
Add your MP3 files
Drag them onto the drop area, choose them from your device, or paste them from your clipboard. You can queue several at once. Nothing is sent anywhere — the file stays on this device.
2
Adjust the settings if you want to
The defaults suit most people. Open Advanced to control bitrate, sample rate and channels.
3
Convert and download
Press Convert. Everything happens on your own device — nothing is uploaded. Download files one by one, or grab them all as a ZIP.

Privacy, in plain words

Is it safe? Your MP3 file is not uploaded anywhere

What “uploaded” normally means. On most online converters, pressing the button copies your file across the internet onto a computer owned by that website. That copy is what the word “upload” means, and it is the part nobody explains.

What happens instead. This site does not do it. There is no server here that receives files, so your MP3 file is read, converted and handed back by the browser you are using right now. It never travels — so there is no copy to store, read, leak or hand over.

Check it yourself in ten seconds

Turn off your Wi-Fi after this page has loaded, then convert a file anyway. It still works, because everything needed is already on your device.

The longer explanation of how this works, and the full detail of what is and is not stored on the privacy page.

Why this matters more than it sounds

An audio file is a conversation. Transcribed by machine — which is cheap now — it becomes searchable text about whoever was speaking. It matters more than it sounds, because of what audio files usually are:

Interviews

a source's voice is identifying even when the name is not said

Voice notes and dictation

thinking out loud, never meant for an audience

Therapy and consultation recordings

clinical material with strict handling rules

Meeting audio

internal discussion, named people, unannounced decisions

A file that is never sent cannot be kept, leaked, subpoenaed or used to train anything. That is a property of how this works, not a promise about how carefully it is run.

MP3 and Opus explained

MP3 is the lossy audio format that made digital music portable. Its patents expired in 2017, which is part of why it remains ubiquitous — anyone can implement it freely.

Opus is the current state of the art for lossy audio, and the codec behind most voice calls you make over the internet. It performs well across an unusually wide range, from 6 kbps speech to transparent music.

Where MP3 files come from: Music libraries, podcasts and voice recordings.
Where Opus is used: Voice and video calls, modern podcast pipelines and WebRTC.

MP3 vs Opus

The two formats solve different problems, which is why converting between them involves trade-offs rather than a straight upgrade.

MP3 compared with Opus
Property	Source	Target
Compression	Lossy	Lossy
Introduced	1993	2012
Browser support	Plays absolutely everywhere.	Modern browsers and apps; older hardware may not.

MP3 is stronger at: Plays on absolutely everything, including old hardware. Small files. No licensing constraints since 2017.
Opus is stronger at: Best-in-class quality at low bitrates. Extremely low latency, which is why calls use it. Royalty-free.

Why convert MP3 to Opus?

People make this switch when they run into the limits of MP3: archiving masters, or editing audio you will re-export repeatedly. Opus is the better fit when voice content, or any situation where bandwidth is tight.

MP3 limitations that prompt the switch: Lossy — discarded detail cannot be recovered. Beaten on quality-per-byte by AAC and Opus. No native support for multichannel audio in practice.
What you give up: Older hardware and car stereos generally cannot play it. Less recognised by users than MP3.

Does converting MP3 to Opus reduce quality?

Both MP3 and Opus are lossy, so this is a re-encode: the file is decoded and compressed again. At the default quality setting the difference is very hard to see, but each successive re-encode compounds. If you will need the file again later, keep the MP3 original rather than converting back and forth.

Measured, not estimated

What converting MP3 to OPUS actually costs

The OPUS came out 1.5× larger than the file that went in.

Each row is one sample chosen to isolate a property these formats treat differently.
Sample	MP3 in	OPUS out	Change
An easy clipThe compressible end of the range — a clean tone, or a moving test pattern — where a codec does its best work.	32.3 KB	47.8 KB	+48%
A hard clipThe other end — pink noise, or dense video grain. Close to incompressible by design, and the worst case for every codec.	32.3 KB	47.8 KB	+48%

Produced by this site's own converter. The same code that runs in your browser, at the same default settings, so these are the bytes you would download.

Samples are generated from a fixed seed rather than taken from real photographs or documents, so the corpus is reproducible and carries no licensing question — and so the numbers predict the shape of your result rather than its exact size. Measured 2026-10-01. The method, and the command that regenerates every figure on this page, are on the how it works page.

About these formats

Source

MPEG-1 Audio Layer III

The universal lossy audio format.

Extensions: .mp3
MIME type: audio/mpeg
Best for: Music players · Podcasts · Maximum compatibility
Compatibility: Plays absolutely everywhere.

Target

Opus Audio

The best low-bitrate codec available — voice and music.

Extensions: .opus
MIME type: audio/opus
Best for: Voice calls · Podcasts · Very small files
Compatibility: Modern browsers and apps; older hardware may not.

Good to know

MP3 to Opus Converter — questions

How do I convert MP3 to Opus?

Drop your MP3 file onto the area above, then press Convert. The Opus file saves straight to your device. You do not need an account, and there is no watermark.

Is it safe to convert MP3 files here — are they uploaded to a server?

No, nothing is uploaded. On most online converters, pressing the button copies your file across the internet onto a computer owned by that website; it is converted there and sent back. That copy is what "upload" means, and it is the part that puts your file out of your control. This site does not do it. Your MP3 file is read and converted by the browser you are using right now and never leaves this device, so there is no copy for anyone to store, read or hand over. You can prove it: turn off your Wi-Fi after this page loads and the conversion still works.

Can I convert confidential MP3 files, like bank statements or contracts?

Yes, and that is the case this site was built for. Because the file never leaves your device, a confidential document is no more exposed than it is sitting in your own folder — there is no transfer, no copy on someone else's hardware, no retention period to read about and no staff with access. Nothing is logged about the file either: not its name, not its size, not its contents. The one thing worth saying plainly is that this protects the file in transit and at rest on our side, not from anything already on your own computer.

Does converting to Opus reduce quality?

Opus uses lossy compression, so some data is discarded. At the default quality the difference is very hard to see or hear; raise the quality setting if you need to be certain, at the cost of a larger file.

How large a file can I convert?

Up to 300 MB per file for this conversion. Because the work happens in your browser, the practical limit is your device's memory — larger files work on a desktop with plenty of RAM and may fail on an older phone.

Can I convert several files at once?

Yes. Add as many as you like and press Convert All. Each file is processed independently, so one failure does not stop the rest, and you can download everything together as a ZIP.

Can I use this on my phone?

Yes. FileTools360 works in mobile browsers on iOS and Android. Pick the file from wherever your phone stores it — Files on iOS, or your downloads folder on Android. Long recordings may run out of memory on an older phone.