Lossless is a type of compression that reduces file size without discarding any data. When you decompress a lossless file, you get back a bit-for-bit identical copy of the original. Nothing is removed, nothing is approximated. The concept applies to audio, images, video, and general-purpose data, but most people encounter the term when choosing music formats or streaming quality.
How Lossless Compression Works
All compression works by finding patterns in data and representing them more efficiently. Lossless compression identifies redundant information and encodes it in a shorter form, like replacing “AAAAAB” with “5A1B.” The key constraint is that every technique used must be perfectly reversible. The decoder takes the compressed file and reconstructs the original data exactly.
There’s a mathematical floor to how small a lossless file can get. Information theory established that the limit of compression is determined by the entropy (the true information content) of the data. You can’t compress past that point without throwing something away. In practice, lossless compression typically shrinks files to about 50 to 70 percent of their original size, depending on the content.
Lossless vs. Lossy Compression
Lossy compression takes a fundamentally different approach: it permanently removes data deemed less important to human perception. JPEG images discard fine high-frequency detail your eyes are unlikely to notice. MP3 audio strips out sound frequencies that are masked by louder sounds playing at the same time. The result is dramatically smaller files, but the discarded information is gone forever. You can never recover it.
Lossless compression keeps everything. A FLAC audio file and the original CD track contain identical audio data. A PNG image and the original bitmap are pixel-for-pixel the same. This distinction matters most when files will be edited, archived, or converted in the future. Every time you re-save a lossy file, it loses a little more quality. Lossless files can be copied, moved, and converted indefinitely without degradation.
The tradeoff is file size. One hour of lossless video (using formats like JPEG 2000 Lossless or FFV1) takes up roughly 53 GB of storage. The same hour in MPEG-2, a lossy format, runs about 23 GB. For audio, a CD-quality lossless track has a bitrate of 1,411 kbps. A high-quality MP3 tops out around 320 kbps.
Can You Actually Hear the Difference?
This is the question that fuels endless debate. In controlled listening tests (called ABX tests, where listeners try to identify which of two samples is the original), results are mixed. Trained listeners in formal studies have been able to distinguish lossy audio from the original at bitrates like 160 and 192 kbps. At higher bitrates, the gap narrows considerably. Many listeners in these tests produce statistically insignificant results even at 128 kbps, meaning they couldn’t reliably tell compressed from uncompressed.
That said, some listeners, some recordings, and some playback equipment do reveal differences. Tracks with complex high-frequency content (cymbals, strings, breathy vocals) tend to expose lossy compression more than simple recordings. Whether lossless matters to your ears depends on your equipment, your hearing, and how closely you’re paying attention. For most casual listening through earbuds, the difference is subtle at best. On a high-quality home audio system with a quiet room, it becomes more noticeable.
Common Lossless File Formats
Lossless formats exist across every media type:
- Audio: FLAC (Free Lossless Audio Codec) is the most widely supported option, open-source and compatible with most devices and players. ALAC (Apple Lossless Audio Codec) serves the same purpose within Apple’s ecosystem. WAV and AIFF are uncompressed formats that are also lossless but don’t reduce file size at all.
- Images: PNG is the standard lossless image format for the web, preserving every pixel. TIFF is common in photography and printing workflows. RAW camera files are also lossless, capturing everything the sensor recorded.
- Video: FFV1 and JPEG 2000 Lossless are used in archival and preservation work. Institutions like the Library of Congress, the National Archives UK, and the City of Vancouver Archives rely on these formats to preserve video without generational loss.
- General data: ZIP, GZIP, and 7z are lossless compression formats for any type of file. When you zip a folder, every byte comes back intact when you unzip it.
Lossless Audio Streaming in 2025
Most major music streaming services now offer lossless tiers. The baseline is CD quality: 16-bit audio sampled at 44.1 kHz, which works out to 1,411 kbps. Hi-res lossless goes further, with higher bit depths and sample rates that capture more detail.
Apple Music streams up to 24-bit/192 kHz, its highest “Hi-Res Lossless” tier, included at no extra cost. Tidal offers hi-res streams typically at 24-bit/96 kHz, with some tracks reaching 192 kHz. Amazon Music Unlimited provides 24-bit hi-res through its “Ultra HD” tier. Qobuz, which targets audiophiles specifically, also streams up to 24-bit/192 kHz. Spotify finally launched lossless in September 2025, offering up to 24-bit/44.1 kHz. Deezer remains at CD quality (16-bit/44.1 kHz), while YouTube Music maxes out at 256 kbps lossy.
One practical consideration: hi-res lossless streams use significantly more data than standard quality. If you’re on mobile data or have limited bandwidth, the difference in download size is real even if the difference in perceived sound quality is not. Most services let you set separate quality levels for Wi-Fi and cellular streaming.
When Lossless Actually Matters
Lossless is essential in professional and archival contexts. Audio engineers need lossless source files because every edit, mix, and export introduces another round of processing. Starting from a lossy file means starting from already-degraded material. The same logic applies to photo editing, video post-production, and medical imaging, where diagnostic accuracy depends on preserving every detail the scanner captured.
For personal use, lossless matters most as a preservation format. If you rip your CD collection to FLAC, you can always convert those files to any future format without quality loss. If you ripped to MP3 instead, you’re locked into whatever quality you chose at the time. Think of lossless as the master copy. You can always make a smaller lossy version from it, but you can never go the other direction.
For everyday listening, the value of lossless depends on your setup and priorities. If you’re using quality headphones or speakers in a quiet environment and you care about getting the most from your music, lossless gives you the peace of mind that nothing was left on the table. If you’re listening through laptop speakers on a bus, the bandwidth is better spent elsewhere.