Compression · Knowledge
What Is File Compression?
Compression is how photos, videos, audio, and documents fit email limits, CMS uploads, and slower connections. Format Convertly’s browser compressors re-encode locally so you can trade size for quality without uploading the file.
Quick take: Compression reduces file size. Lossless keeps a perfect reconstructable original; lossy keeps a smaller approximation that is usually good enough for sharing.
What compression actually changes
A compressor rewrites bytes so the same (or nearly the same) content takes less disk space. Archives like ZIP often use lossless packing. Media compressors usually re-encode with a codec — JPEG, H.264, MP3 — that may discard detail on purpose.
Compression vs conversion
Conversion changes format or container (PNG→JPG, MOV→MP4). Compression focuses on size, often staying in a delivery-friendly format. Many tools do both at once — for example compressing a PNG by saving a smaller WebP.
When to compress
Use compression before web uploads, chat shares, course portals, and email attachments. Keep an uncompressed or lightly compressed master when you still need edits or archives.
Key points
- Compression targets smaller files; conversion targets format change.
- Lossless packing restores originals; lossy delivery discards detail.
- Compress a copy for sharing — keep a master when quality still matters.
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.
Shrink large PDFs locally with a quality slider before email or upload.
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.
Related compression guides
Related quality guides
Related concepts
FAQ
Is compressing the same as zipping?
Not always. ZIP/GZIP pack files losslessly. Image, video, and audio compressors usually re-encode media and may be lossy.
Do Format Convertly compressors upload my files?
No. Compression runs in your browser — nothing is queued on a remote server.
Browse all compression guides, compressors, or quality guides.