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Opus to FLAC Converter

Turn Opus files into FLAC in a couple of clicks. Opus is the best low-bitrate codec available — voice and music; FLAC is losslessly compressed audio — CD quality at roughly half the size. The conversion is lossless — every pixel, sample or byte in the source is preserved.

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

Drop your files here

Opus files (.opus) · up to 300 MB each

or paste files from your clipboard

Ready when you are

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

⌘K to search converters

How to use it

  1. 1

    Add your Opus 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. 2

    Adjust the settings if you want to

    The defaults suit most people. Open Advanced to control bitrate, sample rate and channels.

  3. 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 Opus 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 Opus 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:

Unreleased music

work whose commercial value depends on control of the master

Call recordings

both sides of a conversation, often legally sensitive

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

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.

Opus and FLAC explained

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.

FLAC compresses audio losslessly, typically to about half the size of WAV. Decompressed, it is bit-for-bit identical to the original — the compression is mathematical, not perceptual.

Where Opus files come from
Voice and video calls, modern podcast pipelines and WebRTC.
Where FLAC is used
Hi-fi music libraries and archival rips of physical media.

Opus vs FLAC

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

Opus compared with FLAC
PropertySourceTarget
CompressionLossyLossless
Introduced20122001
Browser supportModern browsers and apps; older hardware may not.Great on desktop and Android; iOS support is newer.
Opus is stronger at
Best-in-class quality at low bitrates. Extremely low latency, which is why calls use it. Royalty-free.
FLAC is stronger at
Lossless — provably identical to the source. Roughly half the size of WAV. Rich metadata and cover art support.

Why convert Opus to FLAC?

People make this switch when they run into the limits of Opus: playback on older or embedded hardware. FLAC is the better fit when archiving music you may want to re-encode later, or storing CD rips.

Opus limitations that prompt the switch
Older hardware and car stereos generally cannot play it. Less recognised by users than MP3.
What you give up
Much larger than MP3 or AAC. Not supported natively by all portable devices.

Does converting Opus to FLAC reduce quality?

Going from Opus to FLAC moves already-compressed data into a format that stores it exactly. Nothing is lost from this point on, but nothing is recovered either — the detail Opus discarded when the file was first created is gone permanently. Expect a noticeably larger file for identical audio quality.

Measured, not estimated

What converting OPUS to FLAC actually costs

On every sample measured, the FLAC came out larger — 6.7× larger at best and 16× larger at worst.

Each row is one sample chosen to isolate a property these formats treat differently.
SampleOPUS inFLAC outChange
An easy clipThe compressible end of the range — a clean tone, or a moving test pattern — where a codec does its best work.17.8 KB119 KB6.7×
A hard clipThe other end — pink noise, or dense video grain. Close to incompressible by design, and the worst case for every codec.16.5 KB262 KB16×

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

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.

Target

Free Lossless Audio Codec

Lossless compression — CD quality at roughly half the size.

Extensions
.flac
MIME type
audio/flac
Best for
Hi-fi music libraries · Archiving · Audiophiles
Compatibility
Great on desktop and Android; iOS support is newer.

The output is a lossless container, but the audio inside it was already compressed. You get a bigger file, not better sound.

Good to know

Opus to FLAC Converter — questions

How do I convert Opus to FLAC?

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

Is it safe to convert Opus 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 Opus 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 Opus 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.

What should I know before converting Opus to FLAC?

The output is a lossless container, but the audio inside it was already compressed. You get a bigger file, not better sound.

Does converting to FLAC reduce quality?

No. FLAC is a lossless format, so the conversion preserves exactly what is in your Opus file. Note that it cannot recover detail that was already discarded when the Opus was first created — a lossless container does not undo earlier compression.

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.

Related converters

All audio converters
FLAC → Opus
Opus → AAC
Opus → AIFF
Opus → M4A
Opus → MP3
Opus → OGG
Opus → WAV
MP4 → FLAC

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FileTools360 by the numbers

527 converters and tools65 file formatsnothing ever uploaded.