Stop Zipping JPEGs: A File‑Type Guide to Effective Compression
Not all files benefit from compression equally. This practical guide helps you decide what to compress, what to simply “store,” and how to balance speed and size so your archives are lean without wasting time.
Why Some Files Shrink (and Others Don’t)
Compression works by finding patterns and redundancies, which text and structured data often contain in abundance. Many modern media formats—like JPEG photos, MP3 audio, and MP4 videos—already apply strong compression internally, so wrapping them in a ZIP rarely reduces size further. In fact, trying to re-compress them can cost extra CPU time and battery life without meaningful savings. On the other hand, plain text, CSV, JSON, source code, and logs are rich in patterns, making them prime candidates for significant size reductions in a ZIP archive.
What to Compress vs. What to Store
Compress these for best results: plain text (TXT), logs, CSV/TSV, JSON/YAML, HTML/CSS/JS, XML, and many proprietary text-based configs. These are typically highly redundant and shrink dramatically. Consider storing (no compression) these to save time with minimal size penalty: JPEG/JPG, PNG, GIF, WebP, HEIC, MP3/AAC/FLAC, MP4/MKV, PDFs that are already optimized, and files that are themselves archives like ZIP, 7z, RAR, or DOCX/XLSX/PPTX (which are ZIP containers under the hood). If you’re unsure, try a quick test on one representative file: compress it once and compare the before/after sizes. If the reduction is negligible (e.g., less than a few percent), use “store” for that file type.
Balancing Speed, Battery, and Size
Compression isn’t free—you pay in CPU time and energy. If you’re archiving large amounts of highly compressible text, using a moderate compression level often yields most of the gains while finishing much faster than the max level. For media-heavy bundles that are mostly JPEGs or MP4s, choose “store” so the archiving step completes quickly and extraction is instant. This approach is especially helpful on laptops and mobile devices where battery life matters. Rule of thumb: compress where the size drops visibly; store where it doesn’t.
Make File‑Type Rules Part of Your Archiving Routine
You don’t need to fine‑tune every file by hand. Create a simple list of extensions that should be compressed (txt, csv, json, xml, html, css, js) and another list that should be stored (jpg, jpeg, png, gif, webp, mp3, mp4, mkv, pdf, zip, 7z, rar, docx, xlsx, pptx). Applying those rules keeps archives small where it matters and fast where compression adds no value. In WC ZIP, you can assemble archives in the browser and choose the compression method per file or batch by type—use “Deflate” for text‑heavy items and “Store” for already‑compressed media and existing archives. Over time, these habits eliminate wasted work and produce consistent, efficient bundles you can share or deploy with confidence.