Compression · Knowledge
Lossy vs Lossless Compression
This is the core tradeoff behind JPEG, MP3, H.264, PNG, FLAC, and ZIP. Pick lossless for masters and archives; pick lossy when delivery size matters more than bit-perfect recovery.
Quick take: Use lossless when you must recover every bit later. Use lossy when a smaller shareable file is the goal and some detail can go.
Lossless in practice
PNG, FLAC, ZIP, and many document packs store a reversible representation. Great for logos, text screenshots, audio masters, and backups — files can stay large.
Lossy in practice
JPEG, lossy WebP/AVIF, MP3, AAC, and typical video encodes discard data. You get dramatic size savings for photos, podcasts, and uploads — you cannot reconstruct the discarded detail later.
How Format Convertly tools behave
Image, video, and audio compressors expose quality or bitrate-style controls that bias toward lossy delivery sizes. PDF compression re-encodes page imagery for smaller documents. Keep originals when you still need a master.
Key points
- Lossless = reversible; lossy = smaller approximation.
- Photos/video/audio delivery is usually lossy.
- Never replace a master with a heavily lossy export.
Open a compressor
Shrink files privately in your browser — pick a category, then a format tool when you know the extension.
Shrink photos and graphics in your browser — format-specific tools for JPG, PNG, WebP, HEIC, and AVIF.
Re-encode common video containers to a smaller MP4 in your browser.
Re-encode audio to a smaller MP3 — podcasts, voice notes, and music shares.
Shrink large PDFs locally with a quality slider before email or upload.
Related compression guides
Related quality guides
Related concepts
FAQ
Is WebP lossy or lossless?
Both modes exist. Lossy WebP behaves like an efficient JPEG-family encode; lossless WebP preserves pixels like PNG.
Is MP3 ever lossless?
No. MP3 is a lossy audio format. Use FLAC or WAV for lossless audio archives.
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