Audio File Formats Explained: MP3 vs WAV vs FLAC vs AAC

The World of Digital Audio

Digital audio has come a long way since the early days of pulse-code modulation in the 1960s. Today, anyone with a smartphone carries a music library that would have occupied an entire room full of vinyl records just decades ago. Yet the sheer variety of audio formats available — WAV, FLAC, MP3, AAC, Opus, and many others — can leave even experienced creators scratching their heads. Each format represents a different set of trade-offs between fidelity, file size, compatibility, and purpose. Understanding those trade-offs is the key to making smart decisions about how you store, share, and produce sound.

The Fundamentals: How Sound Becomes Data

Before examining individual formats, it helps to understand the three pillars of digital audio quality. The sample rate, measured in kilohertz, determines how many snapshots of the analog waveform a system captures each second. The CD standard of 44.1 kHz was chosen because it satisfies the Nyquist theorem for the roughly 20 kHz upper limit of human hearing, while 48 kHz became the norm in video production for historical synchronization reasons. Higher rates such as 96 kHz or 192 kHz extend the captured frequency range well beyond audibility; whether that translates into perceptible improvement remains a lively debate among audiophiles, though the extra headroom can be genuinely useful during production and mixing.

Bit depth governs dynamic range — the gap between the quietest and loudest sound a recording can faithfully represent. At 16 bits, CD audio offers roughly 96 dB of dynamic range, more than ample for consumer listening. Professional workflows lean on 24-bit recording, which pushes that ceiling to around 144 dB, providing a generous noise floor during tracking and mixing so that engineers can capture soft ambiences and loud transients in the same take without clipping. Some modern DAWs even work internally at 32-bit floating point, making it practically impossible to clip a signal during mixing.

For compressed formats, a third metric comes into play: bitrate, expressed in kilobits per second (kbps). A higher bitrate allocates more data to each second of audio, preserving more detail. Variable bitrate encoding (VBR) takes this a step further by adapting on the fly, spending more bits on complex passages and fewer on silence or simple tones, resulting in a more efficient use of storage without a fixed quality ceiling.

Uncompressed Formats: The Raw Originals

WAV, short for Waveform Audio File Format, is the workhorse of professional audio. Co-developed by Microsoft and IBM in 1991, it stores PCM data with no compression at all, meaning every sample is written exactly as captured. A minute of stereo CD-quality WAV consumes roughly 10 MB, and an hour-long recording can easily exceed 600 MB. Those sizes can be daunting, but the format rewards users with absolute fidelity and near-universal compatibility, from professional DAWs to consumer media players. Where WAV falls short is metadata: its support for tags, artwork, and other embedded information is limited and inconsistent across software.

Apple's answer to WAV is AIFF, the Audio Interchange File Format, released in 1988. Technically, AIFF stores the same uncompressed PCM data as WAV, so there is no inherent quality difference between the two. The practical differences are cultural and organizational: AIFF has historically offered somewhat better metadata support, and it remains the native lossless format in Apple's Logic Pro and GarageBand. If you work primarily on macOS, you may encounter AIFF as a default; otherwise, WAV is the safer choice for cross-platform interoperability.

Lossless Compression: Smaller Files, Zero Sacrifice

Lossless codecs sit at the sweet spot for anyone who cares deeply about quality but would prefer not to dedicate a terabyte drive exclusively to music. FLAC, the Free Lossless Audio Codec, is the most widely supported option. Released in 2001, FLAC uses a combination of linear prediction — where each sample is estimated from preceding samples — and Rice coding to compress the residual difference. The result is a file that is typically 50 to 70 percent the size of the equivalent WAV, yet decompresses to a bit-for-bit identical copy of the original. A 600 MB WAV album, for instance, becomes roughly 250 to 350 MB in FLAC. The format is open-source and royalty-free, which helped it become the standard for archival music collections, audiophile streaming services like Tidal, and high-resolution download stores. It also supports rich metadata, including embedded cover art and ReplayGain tags.

Apple Lossless (ALAC) serves the same purpose within the Apple ecosystem. It achieves compression ratios comparable to FLAC and was open-sourced in 2011, though hardware and software support outside Apple's world remains patchier. For users deeply invested in iTunes, Apple Music, and iOS devices, ALAC offers a frictionless path to lossless playback without converting between ecosystems.

Lossy Compression and the Science of Psychoacoustics

Lossy codecs achieve dramatically smaller file sizes by discarding audio data that, in theory, most listeners will never miss. The strategy behind this rests on psychoacoustic modeling, a branch of science that studies how humans perceive sound. Our hearing has well-documented blind spots: a loud tone at one frequency can render a quieter tone at a nearby frequency completely inaudible, a phenomenon known as frequency masking. Similarly, a loud transient like a cymbal crash can mask softer sounds that occur a few milliseconds before or after it, an effect called temporal masking. Lossy encoders exploit these perceptual gaps aggressively, throwing away information the ear would never register.

MP3: The Format That Changed Everything

MP3, formally MPEG-1 Audio Layer III, did not merely introduce a file format — it reshaped the entire music industry. Standardized in 1993, its encoding pipeline begins by converting audio into the frequency domain via a modified discrete cosine transform (MDCT). A psychoacoustic model then evaluates which frequency components fall below the masking threshold and can be quantized more coarsely or removed entirely. Finally, Huffman coding compresses the remaining data into a compact bitstream.

At 128 kbps, an MP3 file is roughly one-eleventh the size of the CD original — a minute of stereo audio occupies about 1 MB instead of 10 MB. Pushing the bitrate to 320 kbps closes much of the audible quality gap, though trained listeners using high-end equipment can sometimes detect artifacts such as pre-echo or the loss of stereo imaging in complex orchestral passages. Despite its age and the existence of more efficient successors, MP3 remains the most universally compatible audio format on the planet, supported by virtually every device, browser, and media player ever made. It is the safe default when you have no idea what your audience's playback equipment looks like.

AAC: The Refined Successor

Advanced Audio Coding was designed in the late 1990s as a direct improvement on MP3, and it shows. AAC's encoder uses a pure MDCT (without the hybrid filter bank that introduces some inefficiencies in MP3), supports sampling frequencies up to 96 kHz, and handles up to 48 channels. In practice, 128 kbps AAC is widely considered equivalent to 160 kbps MP3, and Apple's iTunes Store settled on 256 kbps AAC as its standard download quality — a bitrate at which the vast majority of listeners cannot distinguish the compressed file from the original in blind tests. AAC is the default codec for YouTube audio, Apple Music's lossy tier, and many streaming platforms, making it the de facto successor to MP3 for everyday listening.

OGG Vorbis and the Open-Source Alternative

Ogg Vorbis emerged in the early 2000s as a patent-free response to MP3 and AAC. Developed by the Xiph.Org Foundation, it delivers quality competitive with AAC — and some tests suggest it outperforms MP3 at bitrates below 128 kbps. Vorbis found a loyal niche in gaming, where its low-latency decoding and zero licensing costs made it a natural fit, and in streaming, where Spotify used it for years as its primary codec. Its weakness is device support: while software players handle it well, hardware support on older portable players and car stereos has been inconsistent.

Opus: The Modern Marvel

If you could choose only one lossy codec going forward, Opus would be a strong candidate. Standardized by the IETF in 2012, it merges the speech-optimized SILK codec (originally from Skype) with the music-oriented CELT codec into a single, seamlessly switchable encoder. Opus delivers startling quality at low bitrates — a 64 kbps Opus stream sounds comparable to a 96 kbps AAC stream — and scales gracefully all the way to 510 kbps for near-transparent music. Its latency can drop as low as 5 milliseconds, making it the codec of choice for WebRTC, VoIP, and real-time communication. It is open, royalty-free, and now supported natively in all major browsers. For podcasts, voice memos, and any application where bandwidth is at a premium, Opus is the clear frontrunner.

Choosing the Right Format for Your Workflow

The best format depends on where your audio is headed. In a professional production pipeline, you should record and mix in uncompressed WAV or AIFF at 24-bit/48 kHz or higher, preserving maximum fidelity through every stage of editing. When delivering a finished master, the destination determines the format: streaming services typically accept WAV or FLAC uploads and handle their own transcoding, while podcast directories expect MP3 at 128 kbps for mono speech or 192 kbps for stereo shows.

For personal music libraries, FLAC offers the ideal balance of quality and storage efficiency, roughly halving the space occupied by WAV while preserving every last sample. If you live inside Apple's ecosystem, ALAC achieves the same result with seamless device compatibility. And if you are building a web application or real-time communication tool, Opus is the modern standard — small, fast, and universally supported in browsers.

For archiving, the principle is simple: always keep a lossless copy. FLAC is the best choice for accessibility and metadata support; WAV is the fallback when maximum compatibility matters more than file size. You can always generate lossy variants from a lossless master later, but you can never recover detail that was discarded by a lossy encoder.

The Cardinal Rule of Format Conversion

One rule transcends all use cases: never transcode from one lossy format to another. Converting an MP3 to AAC, for instance, applies a second round of psychoacoustic modeling to audio that has already been stripped of information, compounding artifacts and degrading quality with no meaningful reduction in file size. Converting a lossy file to a lossless format is equally pointless — you get a larger file without recovering any of the discarded data. The only sensible conversion paths are lossless to lossless (which preserves quality perfectly) and lossless to lossy (which applies a single, controlled quality reduction). Always keep lossless masters and generate compressed variants from them as needed.

Working with Audio Formats in Practice

Format conversion is a routine task for anyone who works with audio, and it need not be complicated. Loopaloo's browser-based Audio Format Converter lets you switch between all the major formats discussed here without installing software, and because all processing happens locally on your device, your files never leave your machine. If you need to extract a specific section of a recording before converting it, the Audio Trimmer handles non-destructive cutting, while the Audio Merger can combine multiple clips into a single file — useful when assembling podcast episodes or DJ sets from individual stems.

The Bottom Line

Audio formats are not merely containers for sound; they embody decades of research in signal processing, information theory, and human perception. WAV and AIFF preserve every last sample at the cost of storage space. FLAC and ALAC compress without sacrifice, making lossless audio practical for everyday use. MP3 traded some fidelity for a revolution in portability, and AAC refined that trade-off further. Opus, the newest contender, pushes the boundary of what is possible at low bitrates while remaining open and royalty-free.

Understanding these formats means you will never again wonder why a file sounds muddy after conversion, or why your podcast feed rejects an upload, or whether that "high-resolution" download is genuinely better than CD quality. The format you choose is a deliberate decision — made once, with knowledge — rather than a coin flip.