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How to Compress Images on Mac

A practical guide to compress images on Mac with built-in tools (Preview + Finder batch actions), plus a more precise option for hitting a target size in KB/MB.

•Image Compression

If you want to compress images on Mac, you already have two built-in options:

  • Preview (best for a single image)
  • Finder Quick Actions / Shortcuts (best for batch compression, including mixed formats)

Method 1: Compress a single image with Preview (fastest)

Step 1: Open the image in Preview

Open an image from Finder, or right-click and choose Open With → Preview.

Open an image in Preview on Mac

Step 2: If the image is too large, resize it first

Resizing dimensions is often the biggest file-size win (and usually looks better than pushing compression too far).

In Preview, go to Tools → Adjust Size…, then reduce the width/height to what you actually need.

Preview showing the image

Adjust Size in Preview

Limitation: This workflow is great for a single image, but it becomes slow for large batches—and it’s hard to consistently hit a strict size target (KB/MB) across many files.

Method 2: Batch compress with Finder Quick Actions / Shortcuts (mixed formats)

Mac also supports batch processing in Finder.

Common batch actions include:

  • Convert Image (convert format)
  • Resize Images (small / medium / large)

Exact options may vary depending on your macOS version and enabled actions.

Step-by-step (Convert Image)

  1. In Finder, select multiple images (mixed formats are OK).
  2. Right-click → Quick Actions → Convert Image.
  3. In the dialog:
    • Choose Format (for example, JPEG)
    • Choose Image Size (Actual Size / Small / Medium / Large)
    • (Optional) toggle Preserve Metadata
  4. Click Convert to ... to start.

Select multiple images in Finder

Finder batch actions for compressing images on Mac

Convert Image dialog: format, size, and convert

The key limitation (important)

This method is mostly “dimension/format batch processing”. It’s useful, but:

  • It’s not friendly for “compress to under X KB/MB”.
  • Results vary depending on the image content and format.
  • It’s harder to run a controlled “as small as possible, but still looks good” workflow.
  • There’s no quality slider or “target file size” input for fine-tuning.

A more precise option: Use PhoEdit for target size (KB/MB) and consistent results

PhoEdit is designed for batch workflows:

  • Upload multiple images at once (mixed formats are OK).
  • Choose a preset for a quick quality/size balance.
  • Or use Custom target file size when you must hit a specific limit.
  • Download a single image or a ZIP for a batch.

Open the tool:

Step-by-step (maximum compression / target KB/MB)

  1. Upload your image(s).
  2. In Compression, choose Custom.
  3. Set a target size (e.g., 500 KB or 1 MB).
  4. Click Download.

Maximum compression and custom target size in PhoEdit

If you want a deeper guide on visually lossless vs. maximum compression (and batch compression), see:

Quick recommendation

  • Only one image? Use Preview.
  • A folder of mixed images and you don’t need a strict size target? Use Finder batch actions.
  • Need batch compression and “under X KB/MB” with a more controlled quality/size balance? Use PhoEdit: Compress Image