JPG compression is a spectrum. Your camera saves at quality 95-100, which preserves every subtle detail but creates unnecessarily large files. Most images look identical at quality 80-85 but are 3-5x smaller. The trick is finding the sweet spot.
For quick, free compression, browser-based tools like fwip work well. Drop your JPG file, and the tool strips metadata (EXIF data, colour profiles) and recompresses at an optimised quality level. The conversion happens locally in your browser — your photos never leave your device.
For more control, you can set a specific quality level. In most image editors — Photoshop, GIMP, Preview — you'll see a quality slider when saving as JPG. Quality 85 is the sweet spot for most photos. Below 70, compression artifacts (blocky areas in gradients and sky) become noticeable. Above 90, the file size increases dramatically for minimal visual improvement.
For web developers, tools like ImageOptim (Mac), jpegoptim (Linux), or Squoosh (browser) offer precise control. The most effective technique is resizing before compressing — a 4000px photo displayed at 800px on a website should be resized to 800-1600px first, then compressed. This alone can reduce file size by 90% or more.
Pro tip: strip EXIF data from photos before sharing online. EXIF metadata can contain GPS coordinates, camera serial numbers, and other information you may not want public.