FormatDrop
How-To Guide

How to Convert FLAC to Opus

FLAC files are perfect archives — lossless, accurate — but large. A FLAC album might be 300 MB; the same album as Opus at 128 kbps is under 40 MB, and most listeners cannot tell the difference. Converting FLAC to Opus is the ideal strategy for a mobile listening library while keeping FLAC masters for archival.

Open FLAC to Opus Converter

Step-by-step instructions

  1. 1

    FFmpeg (command line, any OS)

    Best quality for music: `ffmpeg -i input.flac -c:a libopus -b:a 128k output.opus`. For transparent quality: `-b:a 160k`. For voice/podcasts: `-b:a 32k`. Enable VBR: add `-vbr on`. Batch: `for f in *.flac; do ffmpeg -i "$f" -c:a libopus -b:a 128k "${f%.flac}.opus"; done`.

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  2. 2

    opusenc (reference encoder, FLAC input native)

    opusenc accepts FLAC directly: `opusenc --bitrate 128 input.flac output.opus`. Install: `brew install opus-tools` (Mac) or `sudo apt install opus-tools` (Ubuntu). For music: `opusenc --music --bitrate 128 input.flac output.opus`. The --music flag optimizes for music content.

  3. 3

    foobar2000 with Opus plug-in (Windows GUI)

    Install foobar2000 and the encoder_ffmpeg component. Select FLAC files → right-click → Convert → choose Opus → set bitrate to 128 or 160 kbps. foobar2000's converter preserves metadata tags and cover art.

  4. 4

    fre:ac (Windows/Mac/Linux GUI)

    fre:ac at freac.org supports FLAC input and Opus output natively. Add FLAC files → set output format to Opus → set bitrate → Convert. Metadata is preserved. Good for batch conversion of music libraries.

Why convert FLAC to Opus?

FLAC is your archive. Opus is your listening copy. Convert once, listen everywhere, keep your lossless masters safe.

Your files never leave your device

FormatDrop runs the conversion engine entirely inside your browser using WebAssembly. No file upload. No server. Nothing stored. You can verify this by opening DevTools → Network tab and watching: zero upload requests.

Frequently asked questions

What Opus bitrate matches FLAC quality for music?
Opus at 128 kbps is transparent for most music on high-quality headphones and speakers — indistinguishable from lossless. Opus at 160 kbps is transparent for essentially all listeners. Below 64 kbps you'll notice quality loss on music, but speech remains clear.
Should I delete my FLAC files after converting to Opus?
No — keep the FLAC files as archive masters. FLAC is lossless; Opus is lossy. If you ever want to re-encode at a different bitrate, you can re-encode from FLAC without accumulated quality loss. Storage is cheap — keep both.
Does FLAC metadata transfer to Opus?
With FFmpeg and opusenc, standard Vorbis comment tags (title, artist, album, date, genre, track number) transfer automatically. Album art transfers with `-map_metadata 0`. REPLAYGAIN tags are preserved since Opus also uses Vorbis-format comments.
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