Compression Toolkit

What this does

Estimate how much smaller a folder will get if you compress it — before you commit.

Drop a folder or set of files, get a per-file estimate of savings based on content type. Text and code compress dramatically (70-90% smaller). Photos, videos, and PDFs barely shrink (2-5%). The estimator tells you what's actually worth compressing — and what to leave alone.

How estimation works

1. 1

   Drop a folder or files

   Any combination of file types. The tool reads file sizes and extensions — no actual contents leave your browser.

2. 2

   Per-file estimate appears

   Each file is categorized by type. Text/code shows high savings predictions (70-90%). Photos/video/audio show near-zero. Office docs show middling (10-40%).

3. 3

   Decide what's worth compressing

   If your total folder is 5 GB and the estimator predicts only 4% overall savings, compression isn't worth the time. If it predicts 60%, you save 3 GB.

When to estimate first

What compresses well

Same rules as ZIP — DEFLATE is great on text, useless on already-compressed media.

• Text, code, JSON, XML, CSV

  Best for: 70-90% reduction. Always worth compressing.

• Log files

  Best for: Up to 95% reduction — repetitive patterns ideal for DEFLATE.

• Old Office (.doc, .xls)

  Best for: 30-40% reduction.

• Modern Office (.docx, .xlsx)

  Best for: 10-20% — internal ZIP already compresses these.

• Photos / video / audio

  Best for: Near-zero reduction. Skip ZIP for organization only.

  Watch out: If you really need savings, use format-specific compressors (image, video tools).

• PDFs

  Best for: 5-10% on top of PDF's internal compression.

  Watch out: Use a PDF compressor instead for meaningful savings.

Compression-estimate tips

1. 01

   Estimates assume DEFLATE (ZIP)

   Other algorithms (7z LZMA, zstd, brotli) can do better, especially on already-near-optimal data. Estimator's predictions are conservative.

2. 02

   Bigger files compress slightly better

   DEFLATE works on a sliding window. Bigger files have more repetition patterns to exploit, so a 1 GB log file may compress better than 100 individual 10 MB logs.

3. 03

   Don't compress small files individually

   ZIP has per-file overhead (~50 bytes). For files under 500 bytes, the overhead can exceed the savings. Bundle them first.

4. 04

   Encryption changes compression dramatically

   Already-encrypted files (password-protected ZIPs, encrypted backups) don't compress at all — encrypted data looks random to DEFLATE.