A photo straight from an iPhone or a camera is usually several megabytes. For a website, an email or a chat, a few hundred kilobytes is plenty, and most people cannot see the difference. Here are three ways to get there on a Mac, from free and manual to automatic.
What “without losing quality” really means
JPEG, WebP and AVIF are lossy formats: they make files smaller by throwing away detail your eye is unlikely to notice. Some loss is always happening. The goal is loss you cannot see.
Two things decide how small a file can get before damage shows:
- The quality setting. Dropping from 100 to around 75–85 typically cuts the file dramatically with little visible change. Below that, banding in skies and blocky edges start to appear.
- The format. At the same visible quality, WebP and AVIF are usually smaller than JPEG. See WebP vs AVIF vs JPEG XL.
Resizing helps most of all. A 4000-pixel-wide photo shown in an 1200-pixel column carries more than ten times the pixels it needs.
Method 1: Preview (free, one photo at a time)
- Open the image in Preview.
- Choose File › Export.
- Set Format to JPEG or HEIC, and drag the Quality slider to the left. Preview shows the resulting file size as you drag.
- Click Save.
Preview is fine for a few photos. It cannot export WebP or AVIF, it does not show you the compressed result before saving, and you have to judge the quality yourself.
Method 2: Finder’s Convert Image (free, batches)
- Select the images in Finder.
- Control-click and choose Quick Actions › Convert Image.
- Choose a format (JPEG, PNG or HEIF) and an image size (Small, Medium, Large or Actual Size).
- Click Convert. New copies appear next to the originals.
Quick and built in, but there is no quality control and no modern web formats.
Method 3: Shrinker Pro (free, unlimited)
Shrinker Pro is a free, open-source compressor for the Mac. Drop images on its window and smaller copies come back, with no limits and no account.
Method 4: Shrinker Studio (see it before you save it)
When you care how each image looks, Shrinker Studio takes the guesswork out:
- Open Shrinker Pro, press Open Studio and drop in your images.
- In the Format step, choose the output format and set quality to Looks the same. Studio tests settings and keeps the lowest quality that the ssimulacra2 perceptual metric says still looks identical to the original.
- Check the result with Split or the Difference heat map. The After pane shows the exact file Export will write.
- Give any photo that needs it its own settings, then press Export.
Need a hard limit instead, such as “under 200 KB”? Use Fit under. See how to reduce an image to a size in KB.