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FLV to Opus Converter

Turn FLV files into Opus in a couple of clicks. FLV is an obsolete Flash container; 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

FLV files (.flv) · up to 512 MB each

or paste files from your clipboard

Ready when you are

Drop a FLV 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 FLV 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 FLV 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 FLV 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

Video is the format where the thing being converted is usually a recording of people, and often of people who did not expect a third party to have a copy. It matters more than it sounds, because of what video files usually are:

Unreleased footage

material under embargo or still being edited

Recorded meetings and calls

everything said, by everyone in the room

Interviews

sources and participants who consented to you, not to a website

Security-camera footage

your home or premises, and who was in it

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.

FLV and Opus explained

FLV was the container behind Flash video, which dominated online video until browsers removed Flash support entirely at the end of 2020. Nothing plays FLV natively today.

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 FLV files come from: Video downloaded or archived from the web before roughly 2015.
Where Opus is used: Voice and video calls, modern podcast pipelines and WebRTC.

FLV vs Opus

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

FLV compared with Opus
Property	Source	Target
Compression	Container (depends on codec)	Lossy
Animation	Yes	—
Introduced	2002	2012
Browser support	Effectively dead — nothing plays it natively any more.	Modern browsers and apps; older hardware may not.

FLV is stronger at: Historically small files for their era.
Opus is stronger at: Best-in-class quality at low bitrates. Extremely low latency, which is why calls use it. Royalty-free.

Why convert FLV to Opus?

This is not really a format swap — it is extraction. An FLV file carries a video track and an audio track side by side, and converting to Opus discards the picture and keeps the sound. People do it to turn a lecture, interview, podcast recording or music video into something they can listen to without the video, at a fraction of the file size.

FLV limitations that prompt the switch: Effectively dead — no browser or modern player supports it. Low quality ceiling by current standards.
What you give up: Older hardware and car stereos generally cannot play it. Less recognised by users than MP3.

Does converting FLV to Opus reduce quality?

FLV stores your data exactly; Opus does not. Some detail is discarded permanently in exchange for a much smaller file, which is usually the right trade for sharing and publishing. Keep your FLV original if it is the only copy — the conversion cannot be undone.

Measured, not estimated

What converting FLV to OPUS actually costs

On every sample measured, the OPUS came out smaller — 2.9× smaller at worst and 25× smaller at best.

Each row is one sample chosen to isolate a property these formats treat differently.
Sample	FLV 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.	142 KB	48.8 KB	−66%
A hard clipThe other end — pink noise, or dense video grain. Close to incompressible by design, and the worst case for every codec.	1.2 MB	48.8 KB	−96%

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

Flash Video

Obsolete Flash container. Convert to MP4 to keep it playable.

Extensions: .flv
MIME type: video/x-flv
Best for: Recovering old archives
Compatibility: Effectively dead — nothing plays it natively any more.

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.

The soundtrack is decoded and re-encoded. Quality is limited by whatever the video already contained — extracting to FLAC cannot add detail back.

Good to know

FLV to Opus Converter — questions

How do I convert FLV to Opus?

Drop your FLV 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 FLV 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 FLV 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 FLV 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 FLV to Opus?

The soundtrack is decoded and re-encoded. Quality is limited by whatever the video already contained — extracting to FLAC cannot add detail back.

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 512 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, including choosing files straight from your camera roll. Very large videos may run out of memory on a phone — those are better converted on a laptop.