Is FLAC or Opus better quality?

Different categories. FLAC is lossless — quality is the source quality, bit-perfect. Opus is lossy — quality depends on bitrate. At 128 kbps Opus is near-transparent for most listeners; at 256 kbps it's sonically excellent. But FLAC always wins for archival quality because nothing is discarded.

Is Opus better than MP3?

Yes, at equivalent bitrates. Opus is more efficient — it sounds better at every kilobit-per-second range, especially below 128 kbps. Opus at 96 kbps stereo is comparable to MP3 at 160-192 kbps. The catch is compatibility: MP3 plays on everything, Opus only on modern devices.

Can I convert Opus to FLAC to restore quality?

No. Opus is lossy — data was discarded during encoding. Converting to FLAC creates a lossless container of the (already-lossy) decoded audio. The file is much larger but the audio quality is the same as the Opus source.

Why do voice apps use Opus instead of MP3?

Lower latency (5-66 ms vs MP3's ~100 ms encode/decode), better voice quality at very low bitrates (down to 6 kbps), and built specifically for real-time communication. WebRTC standardized on Opus for this reason.

What's the smallest Opus file size for acceptable music quality?

About 96 kbps stereo for near-transparent quality. 64 kbps is acceptable for casual listening. Below 48 kbps stereo, music quality degrades noticeably. For voice content, 24-32 kbps mono is plenty.

Will FLAC or Opus play on iPhone?

Both, on modern iOS. FLAC works in iOS 11+ via Files app and several music players. Opus is more limited — native iOS support arrived in iOS 17. For broadest iPhone compatibility, use M4A (AAC) instead.

Does Spotify use FLAC or Opus?

Both, depending on tier and platform. Spotify Premium streams Ogg Vorbis at 320 kbps on desktop; mobile sometimes uses Opus for efficiency. Lossless tier (if available) uses FLAC.

FLAC vs Opus: When to Use Each Audio Codec

FLAC vs. Opus compared: lossless audio archiving versus the most efficient lossy codec. When to use each format.

April 14, 2025

FLAC and Opus represent two opposite philosophies in digital audio. FLAC is lossless — every sample preserved, files compressed but reversible. Opus is lossy — small files designed for streaming, voice, and bandwidth-constrained delivery. They serve different jobs.

The TL;DR

FLAC is lossless. Bit-perfect audio at roughly half the file size of WAV. Right for archive, audiophile listening, mastering.
Opus is lossy but the best-in-class modern codec. Smaller and higher-quality than MP3 or AAC at the same bitrate. Right for streaming, voice, real-time communication.
They're not direct competitors. FLAC vs Opus is like comparing a backup format to a delivery format.

What FLAC Is

FLAC (Free Lossless Audio Codec) was developed by the Xiph.Org Foundation, released in 2001. It was the first widely-adopted lossless codec to be patent-free and open-source.

FLAC compresses audio losslessly — decoded audio is bit-identical to the original. No data discarded, no audible compromise. Typical compression: 40-60% of the size of uncompressed WAV.

Key characteristics:

Lossless: decoded audio is byte-identical to source
Compression: ~50-60% of WAV size for typical music
Sample rates: 1 Hz to 655 kHz supported
Bit depths: 4-32 bit
Metadata: Vorbis Comments (powerful, UTF-8 native)
Open source: BSD license, no patent encumbrance

FLAC is the de facto standard for lossless music archive, audiophile distribution, CD ripping, and lossless streaming (Tidal HiFi, Qobuz, Amazon Music HD).

What Opus Is

Opus is a modern lossy audio codec developed by Xiph.Org and Skype, finalized 2012 as IETF RFC 6716. It was designed to be the best general-purpose lossy audio codec — covering voice (down to 6 kbps) to high-quality music (up to 510 kbps) in a single unified codec.

Opus combines two technologies: SILK (for speech) and CELT (for music). The encoder picks the appropriate mode based on signal characteristics.

Key characteristics:

Lossy: data discarded for compression
Bitrate range: 6 kbps to 510 kbps
Sample rates: 8, 12, 16, 24, 48 kHz
Container: usually Ogg (.opus), sometimes WebM
Open source, royalty-free
Real-time capable: 5-66 ms latency, ideal for VoIP

Opus is dominant for modern voice and music streaming: WebRTC voice calls (Discord, Google Meet), Spotify mobile streaming, YouTube alongside AAC, and modern web audio.

Sound Quality Compared

FLAC is sonically identical to the source WAV (bit-perfect). Quality is the source quality.

Opus is lossy but extremely efficient:

| Bitrate | Opus quality | |---|---| | 16-24 kbps | Excellent voice; recognizable music | | 32-48 kbps | Good voice; acceptable music | | 64-96 kbps | Excellent voice; good music | | 128 kbps | Near-transparent music for typical listeners | | 160-192 kbps | Sonically transparent for nearly all listeners | | 256 kbps+ | Archival lossy quality |

Opus at 96-128 kbps stereo is comparable to AAC at 128-160 kbps or MP3 at 192-256 kbps. The efficiency advantage is biggest at low-to-mid bitrates.

FLAC = source quality. Opus = best lossy quality per kilobit available today.

File Size Comparison

For a 4-minute song:

| Format | Size | |---|---| | WAV (16-bit, 44.1 kHz stereo) | 42 MB | | FLAC | 22 MB | | ALAC | 23 MB | | Opus @ 128 kbps | 3.8 MB | | Opus @ 96 kbps | 2.9 MB | | Opus @ 64 kbps | 1.9 MB | | MP3 @ 320 kbps | 9.6 MB | | MP3 @ 192 kbps | 5.7 MB |

Opus at 96 kbps is roughly 10× smaller than FLAC for the same audio. But Opus is lossy — the file contains decoded approximations, not the original samples.

When to Use FLAC

Music archival. Long-term storage of CD rips, original recordings, masters.

Audiophile distribution. Tidal HiFi, Qobuz, and Bandcamp lossless tier all use FLAC.

DAW import from lossless source. Editing audio in a DAW from a FLAC source preserves quality through processing.

Mastering deliverables. Mastering engineers often deliver FLAC alongside WAV.

Streaming platform submission. Most music distribution platforms accept FLAC for upload.

Backup of vinyl, tape, or live recordings.

When to Use Opus

Voice over IP. Opus is the dominant VoIP codec because of low latency and excellent voice quality at low bitrates.

Streaming music to mobile devices. Efficiency matters over cellular.

Podcast distribution at low bitrates. Opus at 32-48 kbps mono is plenty for spoken word, much smaller than equivalent MP3.

Web audio with HTML5 audio tag. Modern browsers support Opus natively (Safari 14+).

YouTube. YouTube uses Opus for many of its audio streams.

Audio podcast in WebM/Ogg containers. Maximum quality per kilobit.

Game audio. File size matters for downloadable content.

When NOT to Use Each

Don't use FLAC for:

Streaming to bandwidth-constrained mobile devices

Email attachments where file size matters

Web audio for casual listening (use Opus or AAC)

Don't use Opus for:

Long-term archive

Mastering source

Audiophile listening where bit-perfect matters

Distribution to legacy hardware (most car stereos don't support Opus)

Compatibility Compared

FLAC compatibility:

All modern desktop OSes: Native
Modern web browsers (Safari 11+): Native
Android 3.1+: Native
iOS 11+: Files app yes, iTunes no
Most car stereos: Mixed
Legacy MP3 players: No

Opus compatibility:

Modern web browsers: Native
Android 5+: Native
iOS 17+: Native; iOS 11-16 limited (third-party apps)
Windows 10+: With recent codec packs
Most car stereos: No
Legacy hardware: No

For broadest device compatibility: MP3 still wins. For modern browsers and apps: both FLAC and Opus work.

How to Convert Between FLAC and Opus

If you have a FLAC file and need Opus, encode at 96-128 kbps stereo for music or 32-48 kbps mono for voice.

If you have an Opus file and need FLAC, the conversion preserves the Opus quality but doesn't restore the original (lossy) source. The FLAC output is much larger than the Opus input.

For ffmpeg:

``` ffmpeg -i input.flac -c:a libopus -b:a 128k output.opus ```

``` ffmpeg -i input.opus -c:a flac output.flac ```

Summary

FLAC and Opus solve different problems. FLAC is the lossless format for archival, audiophile distribution, and quality-critical workflows. Opus is the modern lossy codec for streaming, voice, and bandwidth-constrained delivery — the best quality-per-kilobit available today. They're complementary: use FLAC for storage and Opus for delivery.