Audio files come in dozens of formats, and each situation demands something different: streaming services want AAC, podcasts require MP3, audio engineers need WAV or AIFF, archivists prefer FLAC, and voice chat apps use OPUS. ChangeThisFile converts between all major audio formats using FFmpeg — free, server-side, with no signup and no retained files.
All audio conversion happens on our servers. Your file is uploaded over encrypted HTTPS, converted by FFmpeg, and the output is returned to your browser. The original and converted files are automatically deleted after conversion. The 50MB upload limit applies to audio files.
Supported Audio Formats
ChangeThisFile converts between all of the following audio formats. Click any conversion pair to go directly to that converter:
- MP3 — The universal audio format. Compatible with every device, player, and platform. Lossy compression at 128-320kbps. Convert: MP3 to WAV, MP3 to AAC, MP3 to FLAC, MP3 to OGG, MP3 to OPUS, MP3 to M4A, MP3 to WMA, MP3 to AIFF.
- WAV — Uncompressed PCM audio. Lossless quality, large files. The standard format for audio editing and professional production. Convert: WAV to MP3, WAV to AAC, WAV to FLAC, WAV to OGG, WAV to OPUS, WAV to M4A, WAV to WMA, WAV to AIFF.
- AAC — Advanced Audio Coding. The default format on iPhones, iTunes, and YouTube. Better quality than MP3 at the same bitrate. Convert: AAC to MP3, AAC to WAV, AAC to FLAC, AAC to OGG, AAC to OPUS, AAC to M4A, AAC to WMA, AAC to AIFF.
- OGG (Vorbis) — Open-source lossy format. Used by Spotify, Bandcamp, and many games. No patents, free to implement. Convert: OGG to MP3, OGG to WAV, OGG to AAC, OGG to FLAC, OGG to OPUS, OGG to M4A, OGG to WMA, OGG to AIFF.
- FLAC — Free Lossless Audio Codec. Lossless compression — identical quality to WAV at ~50-60% the file size. The standard for lossless archiving. Convert: FLAC to MP3, FLAC to WAV, FLAC to AAC, FLAC to OGG, FLAC to OPUS, FLAC to M4A, FLAC to WMA, FLAC to AIFF.
- OPUS — The modern voice and music codec. Best quality at low bitrates (6-510kbps). Used by Discord, WhatsApp, and WebRTC. Open and royalty-free. Convert: OPUS to MP3, OPUS to WAV, OPUS to AAC, OPUS to FLAC, OPUS to OGG, OPUS to M4A, OPUS to WMA, OPUS to AIFF.
- M4A — MPEG-4 Audio. AAC audio in an MPEG-4 container. Apple's default audio format for iTunes purchases and Apple Music downloads. Convert: M4A to MP3, M4A to WAV, M4A to AAC, M4A to FLAC, M4A to OGG, M4A to OPUS, M4A to WMA, M4A to AIFF.
- WMA — Windows Media Audio. Microsoft's proprietary format. Legacy format from Windows Media Player era, still found in older music libraries. Convert: WMA to MP3, WMA to WAV, WMA to AAC, WMA to FLAC, WMA to OGG, WMA to OPUS, WMA to M4A, WMA to AIFF.
- AIFF — Audio Interchange File Format. Apple's uncompressed format. Equivalent to WAV but preferred in macOS/Logic Pro environments. Convert: AIFF to MP3, AIFF to WAV, AIFF to AAC, AIFF to FLAC, AIFF to OGG, AIFF to OPUS, AIFF to M4A, AIFF to WMA.
Lossy vs Lossless Audio Formats
The most important concept in audio conversion is the lossy vs lossless distinction. It determines whether quality is permanently lost during conversion.
Lossy Formats: Smaller Files, Permanent Quality Loss
Lossy formats (MP3, AAC, OGG, OPUS, WMA) compress audio by permanently discarding inaudible or less-important audio data. A 10MB WAV file might become a 1MB MP3 — a 90% reduction. The tradeoff: the discarded data is gone forever. Converting a lossy file to another lossy format compounds the quality loss (called "generation loss"), because the encoder is working with already-degraded audio.
Key rule: Never convert lossy to lossy unless compatibility requires it. Converting MP3 to AAC for streaming won't improve quality — it will slightly degrade it. Convert from lossless originals (WAV, FLAC, AIFF) to your target lossy format instead.
| Format | Algorithm | Typical Bitrate | Use Case |
|---|---|---|---|
| MP3 | MPEG-1 Layer III | 128-320 kbps | Universal compatibility |
| AAC | Advanced Audio Coding | 128-256 kbps | Apple ecosystem, streaming |
| OGG | Vorbis | 64-500 kbps (VBR) | Gaming, open-source projects |
| OPUS | IETF RFC 6716 | 6-510 kbps | Voice chat, WebRTC, streaming |
| WMA | Windows Media Audio | 48-320 kbps | Legacy Windows audio |
Lossless Formats: Perfect Quality, Larger Files
Lossless formats (WAV, FLAC, AIFF) compress audio without discarding any data. A FLAC file decoded to WAV is bit-for-bit identical to the original — there's no quality difference between them, only a file size difference.
Converting between lossless formats is always safe. Converting WAV to FLAC to save space, then FLAC back to WAV for editing, introduces zero quality loss. This makes lossless formats ideal for archiving and editing source material.
| Format | Compression | Typical Size vs WAV | Use Case |
|---|---|---|---|
| WAV | None (PCM) | 100% (baseline) | Audio editing, professional production |
| FLAC | Lossless | 40-60% of WAV | Archiving, high-res music libraries |
| AIFF | None (PCM) | ~100% (same as WAV) | macOS/Logic Pro environments |
Understanding Audio Quality Settings
When converting to lossy formats, bitrate is the primary quality lever. Higher bitrate = better quality = larger file.
| Bitrate | Quality Level | Best For |
|---|---|---|
| 64 kbps | Low — noticeable artifacts | Voice recordings, podcasts with poor source quality |
| 128 kbps | Acceptable — transparent to most listeners | Casual listening, mobile streaming |
| 192 kbps | Good — transparent to most listeners in most conditions | Music streaming, general use |
| 256 kbps | Very good — near-transparent | High-quality streaming, audiophile casual |
| 320 kbps | Excellent — transparent to all listeners | Maximum quality lossy distribution |
OPUS is different: OPUS achieves CD-quality audio at just 128kbps, and very good voice quality at 24kbps. At 96kbps, OPUS sounds better than 128kbps MP3. It's the most efficient format at low bitrates.
Sample rate and bit depth: CD quality is 44.1kHz / 16-bit. High-resolution audio goes to 96kHz or 192kHz, and 24-bit. For most conversion tasks, preserving the source sample rate and bit depth is correct. Downsampling from 96kHz to 44.1kHz is irreversible — only do it deliberately.
When to Use Each Format
- MP3: When universal compatibility is the top priority. Every device, car stereo, streaming platform, and podcast app supports MP3. Use 192kbps for music, 128kbps for voice/podcasts.
- AAC: When targeting Apple devices, YouTube, or streaming services. Better than MP3 at the same bitrate, and natively supported by all Apple hardware. Use 256kbps for music.
- WAV: When editing audio or delivering to a recording studio. Uncompressed, so no generation loss through edits. The 10x file size vs MP3 is worth it when you're working on a project rather than distributing it.
- FLAC: When archiving your music library in lossless quality. FLAC is ~50% smaller than WAV while being bit-for-bit identical on decode. The format is widely supported by music players and NAS devices.
- OGG: When working with open-source projects or games. Ogg Vorbis has no patent restrictions and is used in many game engines. Also native on Android.
- OPUS: When streaming audio at low bitrates, especially voice. Discord, WhatsApp, and most WebRTC implementations use OPUS. The best codec for voice calls and low-bandwidth streaming.
- M4A: When working within the Apple ecosystem. M4A is AAC in an MPEG-4 container — functionally identical to AAC but with better metadata support. iTunes purchases are M4A.
- AIFF: When working in Logic Pro or a macOS-centric audio workflow. AIFF is Apple's equivalent of WAV — same quality, slightly different metadata handling.
- WMA: Only when compatibility with old Windows Media Player libraries requires it. WMA has no technical advantages over AAC or MP3 and is primarily a legacy format.
Audio Format Size and Quality Comparison
Benchmark: 3-minute stereo music track at 44.1kHz / 16-bit, converted from a lossless WAV source (31.5 MB). File sizes are for the full 3-minute track.
| Format | File Size | Bitrate / Compression | Quality vs Source | Best For |
|---|---|---|---|---|
| WAV (source) | 31.5 MB | 1411 kbps (uncompressed) | Reference | Audio editing, studio delivery |
| AIFF | 31.5 MB | 1411 kbps (uncompressed) | Identical to WAV | macOS / Logic Pro workflows |
| FLAC | 18.2 MB | Lossless (~58% of WAV) | Bit-for-bit identical | Archiving, lossless music libraries |
| MP3 (320kbps) | 7.1 MB | 320 kbps | Transparent to all listeners | Maximum quality distribution |
| AAC (256kbps) | 5.7 MB | 256 kbps | Better than MP3 320kbps | Apple ecosystem, streaming |
| MP3 (192kbps) | 4.3 MB | 192 kbps | Transparent to most listeners | Music streaming, general use |
| OGG (~160kbps VBR) | 3.6 MB | ~160 kbps VBR | Comparable to MP3 192kbps | Games, open-source projects |
| MP3 (128kbps) | 2.9 MB | 128 kbps | Acceptable; artifacts on critical listening | Casual listening, podcasts |
| AAC (128kbps) | 2.9 MB | 128 kbps | Better than MP3 128kbps | Mobile streaming, podcasts |
| OPUS (128kbps) | 2.9 MB | 128 kbps | Best lossy quality at this bitrate | Streaming, voice chat |
| OPUS (96kbps) | 2.2 MB | 96 kbps | Matches MP3 128kbps at 25% smaller | Low-bandwidth streaming |
| WMA (128kbps) | 3.0 MB | 128 kbps | Comparable to MP3 128kbps | Legacy Windows compatibility only |
Key findings: OPUS is the most efficient lossy codec — 96kbps OPUS matches 128kbps MP3 quality at a 25% smaller file. AAC consistently beats MP3 at every bitrate for the same file size. FLAC gives you lossless quality at 58% of WAV's size with zero quality compromise. The only reason to choose WMA is compatibility with old Windows Media Player libraries.
Privacy and Security
All audio conversion on ChangeThisFile runs server-side using FFmpeg. Your audio file is uploaded over HTTPS (encrypted in transit), converted on our servers, and automatically deleted after conversion. We don't store, analyze, or share your audio files. No account is required.
For audio files containing sensitive content (recordings, voice memos, confidential interviews), be aware that the file does travel to and from our servers during conversion. The 50MB upload limit applies. Files over 50MB should be split or compressed before uploading.
ChangeThisFile handles every common audio format conversion: lossy-to-lossless (MP3 to WAV), lossless-to-lossy (WAV to MP3 for distribution), between lossless formats (WAV to FLAC for archiving), and any combination of the nine formats above. Pick your source and target format, upload your file, and download the converted audio — free, no watermark, no signup. For best results when converting to a lossy format, always start from the highest-quality source available.