How JPG compression works
The JPEG format lets you trade a little visual fidelity for a much smaller file. The quality slider controls how aggressively detail is discarded: at 100% almost nothing is thrown away (and the file is large), while at 50% the savings are big but artefacts start to show. The useful insight is that the relationship isn't linear — dropping from 100% to about 85% removes data your eye can't detect, cutting file size substantially with no visible change. Below roughly 70% you start to notice softening and blockiness, especially around edges.
Getting the smallest file that still looks good
Two levers reduce a JPG's size, and they compound:
- Quality — start at 80%. If it still looks perfect, try 75%. Compare the result against the original before committing.
- Dimensions — this is the one people forget. A 6000px-wide photo shown in a 1200px column is wasting four-fifths of its pixels. Set a Max width and the file shrinks far more than quality alone can manage.
If a JPG was already saved at low quality, there's little left to remove and re-compressing gains almost nothing — it may even grow slightly. In that case, resizing is your best remaining lever.
How to compress
- Output is set to JPG at 80%. Adjust the slider to taste.
- Optionally set a max width to resize large photos down.
- Drop your JPGs above. Each shows its before/after size and percent saved.
- Download individually or as a ZIP.
WebP typically beats JPG by 25–35% at the same quality.
Read more in how to compress without losing visible quality and resizing images for the web.