Upload a Opus file and get a FLAC back. No signup, no watermark, no limit on how many.
Opus is the best lossy codec in general use: at 64 kbps it beats formats running at twice that, which is why real-time applications standardised on it.
Where you run into it: WhatsApp and Telegram voice notes, Discord, Signal, Zoom, and most browser-based calls.
What it costs you: Everything can play it inside an app and remarkably little can play it as a file — a voice note saved to a desktop is the classic case, and the usual reason to convert one.
FLAC compresses losslessly: it typically halves a WAV and gives back bit-for-bit the same audio when decoded. It is free, open, and widely supported outside Apple's world.
Where you run into it: Archived rips, Bandcamp and Qobuz downloads, anyone who keeps a music library they intend to still have in ten years.
What it costs you: Half of enormous is still large, and some hardware — car head units especially — will not touch it.
The Opus is decoded — always at 48 kHz, because that is the only rate the codec works at internally — and the result is compressed losslessly. So a voice note recorded at 16 kHz comes out as a 48 kHz FLAC. Opus has no lossless mode of its own, so there is no version of this file that was ever intact: what the FLAC gives you is a very accurate preservation of a lossy recording, at considerable expense in space.
Almost every .opus is a voice message or a Discord recording, and there are two sensible destinations depending on why you have it. If something has to read the audio — a transcription service, an editor, a case file, a research corpus — FLAC is right: it is lossless, it is accepted nearly everywhere, and it can verify itself years later from the checksum it stores. If you only need to keep the recording, keep the .opus, which is a twentieth of the size and exactly as good. What FLAC cannot do is make a quiet or muddy recording any clearer.
Yes, entirely, and there is no cap on how many files you convert. No account, no watermark, no trial.
No further loss and nothing restored. Opus deserves credit in passing: at the 16 to 32 kbps messaging apps use, it holds speech better than any other codec in common use, so what you are preserving is genuinely good for its size. What FLAC adds is not fidelity but reach — Opus is fine inside an app and awkward as a file, and FLAC is accepted by archives, editors and catalogues that will not look at an .opus.
The steepest ratio you will meet here. A one-minute voice note at 24 kbps is around 180 KB; the same minute as a mono 48 kHz FLAC is roughly 3 MB, so expect fifteen to twenty times. The 48 kHz decode accounts for most of it — speech carries nothing above a few kilohertz, so a good part of what the FLAC is carefully preserving is an empty upper band.
Not here. Opus can be read but not written by this converter — ffmpeg decodes it happily, and encoding back to it would mean a format almost nothing plays. If you need the original Opus, keep it rather than recreating it.
The file is uploaded to do the conversion — nothing here runs in your browser — and both your upload and the converted result are deleted the moment the file is sent back. Nothing is stored and nothing is logged beyond the request itself.