Melt guide

Reduce image file size on Mac (free + easy options)

Five free ways to shrink images on macOS, ranked by how little you have to install.

4 min read

You don’t want to pay for an app to do something a Mac can mostly do on its own. Fair enough. Here are five ways to reduce image file size on macOS that cost nothing, ordered from “you already have this installed” down.

1. Right-click Quick Action (zero install)

In Finder, right-click an image → Quick Actions → Convert Image. Pick a format (HEIC is the smallest for photos, JPEG for compatibility) and a size preset (Small, Medium, Large, Actual Size).

Pros: literally one click after the right-click. Cons: size presets are pixel dimensions, not file size — Small is 640px wide, which might be too small for many uses.

2. Preview Export (zero install)

Open the image in Preview → File → Export. Pick JPEG, drag Quality to 75-80, watch the file size estimate update. Save.

Pros: live size preview, full control. Cons: one file at a time.

3. Preview batch (zero install)

Select multiple images in Finder, open all in Preview, ⌘A in the sidebar, File → Export Selected Images. Sets the same quality across the whole batch.

Pros: handles 5-50 images comfortably. Cons: same quality for every image regardless of content, gets sluggish past 100.

4. sips from Terminal (zero install)

sips is built into macOS. One line:

sips -s format jpeg -s formatOptions 75 -Z 2000 input.jpg —out output.jpg

For a folder:

for f in *.jpg; do sips -s format jpeg -s formatOptions 75 -Z 2000 “$f” —out “small/$f”; done

Pros: scriptable, fast, handles thousands of files. Cons: it’s Terminal — no preview, no progress, unforgiving.

5. ImageOptim (free download)

ImageOptim is free, open-source, and does aggressive compression. Drag a folder in, it compresses in place using pngquant, MozJPEG and friends.

Pros: best compression of the free options. Cons: in-place only (no separate output folder), no resize, no format conversion, no per-batch settings.

When free stops being enough

For occasional one-offs, the above are genuinely fine. The point at which it makes sense to spend $9.99 on Melt is when:

  1. Download Melt if you want to try the paid option.
  2. Drag any mix of images in.
  3. Pick format, quality, optional resize.
  4. Click Compress.

How much smaller will it really get?

The compression results are roughly equivalent across all five options for the same quality setting — they’re using overlapping codecs. What differs is the friction. For one file once a month, use Preview. For one file once a day, learn sips. For folders of mixed formats every week, pay for the tool that does it without thinking.

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