FLAC to Opus Converter

How to Convert FLAC to Opus Online

1. Upload Your FLAC File: Drag and drop or click "Choose Files" to select one or more .flac files. Batch conversion is supported — queue several albums at once.
2. Pick a Quality Preset or Bitrate: Default is the Quality Preset (Highest through Lowest). For finer control, switch to Constant Bitrate (32-384 kbps presets), Variable Bitrate (recommended for music), Custom Bitrate (any value in kbps), Specific file size, or File Size Percentage to target a fraction of the original.
3. Adjust Audio Channel and Sample Rate (Optional): Audio Codec is locked to Opus. Set Audio Channel to Original, Mono, or Stereo. Set Audio Sample Rate to 8000, 12000, 16000, 24000, or 48000 Hz — Opus internally resamples to 48 kHz, so 48000 is the native target.
4. Trim and Convert: Optionally enable Trim and enter a Start Time and Duration (seconds or HH:MM:SS.sss). Click Convert. Files are uploaded over an encrypted connection, processed on our servers, and deleted automatically after a few hours — no sign-up, no watermark, never shared.

Why Convert FLAC to Opus?

FLAC (Free Lossless Audio Codec) preserves every bit of the original PCM signal — a 3-minute song at CD quality (44.1 kHz, 16-bit, stereo) typically lands at 15-30 MB, and high-resolution masters at 96 kHz/24-bit can exceed 100 MB. Opus, standardized by the IETF in RFC 6716, is a modern royalty-free lossy codec that hits transparency at around 128 kbps for stereo music — roughly 5-10% of the FLAC size for content most listeners can't distinguish from the source in blind tests.

• Portable music library that actually fits — a 50 GB FLAC collection compresses to roughly 5 GB as Opus at 96 kbps VBR, leaving room on a 64 GB phone for apps and photos.
• Better quality-per-byte than MP3 or AAC — the Xiph.Org foundation's recommended settings note Opus has higher quality than MP3, AAC, and Vorbis in the 64-96 kbps range. The codec uses a SILK (speech) + CELT (music) hybrid that switches based on content.
• Native web playback — Opus plays directly in <audio> elements in Chrome, Firefox, Edge, and Safari 18.4+ (per caniuse), so converted files stream from any static host without a transcoding step.
• Discord and WhatsApp voice messages — both use Opus internally; encoding music to Opus before sharing avoids a generation-loss re-encode on upload.
• Low-latency streaming and game audio — Opus supports frame sizes from 2.5 ms to 60 ms, making it the codec of choice for WebRTC, Twitch chat, and PS5/Xbox party voice.
• Smaller backups for cars and old iPods running Rockbox — most modern Android head units and Rockbox-flashed players decode Opus natively, freeing space versus FLAC archives.

FLAC vs Opus — Format Comparison

Recommended Opus Bitrate by Use Case

Frequently Asked Questions

What Opus bitrate is truly transparent versus the FLAC source?

For stereo music, Xiph.Org's own guidance is that 128 kbps VBR is "pretty much transparent" — trained listeners struggle to ABX-distinguish it from the lossless source. Most casual listeners find 96 kbps indistinguishable on phone speakers, earbuds, and car systems. If you have studio monitors and reference recordings, 160-192 kbps gives you headroom without doubling file size.

Why does Opus only accept 48 kHz, 24 kHz, 16 kHz, 12 kHz, or 8 kHz when my FLAC is 44.1 kHz?

Opus is internally a 48 kHz codec — the RFC 6716 spec defines no other sample rate for output. When you feed a 44.1 kHz FLAC, the encoder resamples to 48 kHz transparently; the decoder then resamples back to your DAC's rate on playback. There's no audible quality penalty, and 48 kHz is the recommended setting on this page.

Should I use VBR or CBR for music?

Use Variable Bitrate for music. Opus is designed around VBR, and the encoder allocates more bits to complex passages (vocals, transients, orchestral peaks) and fewer to silence or simple content. CBR is only useful when you need a predictable streaming bitrate for live broadcast or strict bandwidth caps; for storage it wastes space.

Why is my converted Opus file so much smaller than a similar MP3?

Opus is roughly twice as efficient as MP3 at low bitrates. Opus at 96 kbps is comparable in perceived quality to MP3 at 192-256 kbps, because Opus uses modern psychoacoustic modeling and a hybrid SILK+CELT structure rather than MP3's 1993-era subband approach. The size reduction is real, not a corrupt file.

What devices and apps actually play Opus in 2026?

VLC, foobar2000, mpv, Audacity, Winamp (5.9+), and every major web browser (Chrome 33+, Firefox 15+, Edge 14+, Safari 18.4+). On mobile: Android has had system-level Opus support since Android 5.0 (2014), and iOS gained native Safari <audio> Opus support in iOS 18.4 (April 2025). Most Android car head units, Sonos, and Rockbox-flashed iPods decode it. If you need a device that doesn't, see FLAC to MP3 or FLAC to AAC instead.

Will my metadata, album art, and ReplayGain tags survive the conversion?

Opus stores tags in an OggOpus comment header that mirrors the Vorbis Comment format. The converter preserves common fields (TITLE, ARTIST, ALBUM, DATE, TRACKNUMBER) and embedded cover art. ReplayGain is preserved as R128_TRACK_GAIN / R128_ALBUM_GAIN per the Opus spec — players like foobar2000, Rockbox, and mpv read these natively.

Can I batch-convert a whole album or library at once?

Yes. Upload multiple FLAC files in step 1 and the converter applies the same settings to each. For a multi-hundred-file library, expect to convert in batches of 20-50 at a time — large hi-res masters take longer to upload and process but there is no hard file-count cap per batch.

Is the conversion truly lossy if I started from lossless?

Yes — Opus is a lossy codec, so the output is not bit-identical to the FLAC input. The benefit of starting from FLAC is that you avoid transcoding loss: re-encoding an already-lossy file (MP3, AAC) to Opus compounds artifacts. Starting from FLAC means Opus operates on the cleanest possible signal, which is why it sounds noticeably better than the same bitrate Opus encoded from an MP3 source.

Why convert FLAC to Opus instead of just compressing the FLAC?

Compressing FLAC at its highest level (compression level 8) typically only shrinks files by 5-10% versus level 5 — FLAC is already near the information-theoretic limit for lossless audio. Switching to Opus at 128 kbps cuts size by 90-95% because lossy codecs discard perceptually inaudible information. Use FLAC compression for archival masters; use Opus when you need the file to be portable.

How does Opus compare to OGG Vorbis?

Both are Xiph.Org codecs and both ship in Ogg containers, but Opus supersedes Vorbis for new encodes — it's higher quality at every bitrate below 128 kbps and is the codec Xiph recommends for new projects. Vorbis remains around for legacy compatibility; see FLAC to OGG if you specifically need Vorbis.