How to batch compress a folder of photos on Mac

You’ve got a folder of 200 product photos straight off a DSLR and you need them all on the web by tomorrow. Doing it one at a time in Preview will take an afternoon. Doing it badly will tank your site’s loading speed.

Two paths

Native macOS. Two real options:

• Preview’s batch. Select all images in Finder, open them in Preview (they appear in the sidebar), Cmd+A to select all, then File → Export Selected Images. Pick JPEG, set a quality, save to a folder. This works but Preview gets sluggish past 50–100 images, and the quality slider is global — every image gets the same setting whether it needs it or not.

• Terminal sips in a loop. Fast and scriptable:

  mkdir compressed
  for f in *.jpg; do
    sips -s format jpeg -s formatOptions 80 "$f" --out "compressed/$f"
  done
  

  Add -Z 2000 to also resize to a max edge of 2000px. Handles thousands of files without breaking a sweat. The downside is no preview, no progress bar, and no safety net — a typo wipes your output folder.

Melt. A drag-and-drop Mac app ($9.99 one-time) built around batch processing. Drag the folder in, pick settings once, run.

Batch compress in Melt

1. Open Melt.
2. Drag the whole folder in — Melt walks the contents and queues every supported image (JPEG, PNG, HEIC, GIF, TIFF).
3. Pick an output format and quality.
4. Optionally enable Resize to cap the longest edge.
5. Click Compress. Progress bar shows per-file results.

The “never makes a file bigger” check applies per-file in batch mode — already-compressed images that would inflate are skipped and kept as-is, so you can run a mixed folder safely.

Honest tradeoffs

Batch processing always means a one-size-fits-most setting. A quality of 80 looks great on photographs but might be too aggressive for a clean illustration with flat colour. If a few images in your folder matter more than the rest, run those separately at a higher quality. For the long tail of “this needs to be on the internet by tomorrow,” batch is exactly what you want.