Compression · Knowledge
Why Compressed Files Lose Quality
People notice quality loss after aggressive JPG saves, low-bitrate video uploads, or repeated MP3 exports. The cause is intentional: lossy codecs throw away data humans are less likely to notice — until settings go too far.
Quick take: Quality drops because lossy compression deletes information. Raise quality/bitrate, resize instead of crushing quality, and always keep a master.
What gets discarded
Fine texture in photos, high-frequency audio detail, and subtle motion differences in video. At moderate settings most viewers are fine; at extreme settings artifacts appear.
Generational loss
Each lossy re-encode can add more damage. Compress once from the best source. Do not download → compress → upload → download → compress again.
What still looks identical
Lossless compression and careful remuxes do not remove perceptual media detail. Large WAVs and PNGs stay big because they keep information.
Key points
- Lossy = permanent detail loss for size.
- Artifacts mean the setting was too aggressive.
- Recovery requires the original master.
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
Can I undo compression?
Not from a lossy output alone. Return to the original file and compress again with gentler settings.
Why does my PDF look blurry after compressing?
Many PDF compressors re-encode pages as JPEG images. Use a higher quality setting for print-critical docs.
Browse all compression guides, compressors, or quality guides.