How to Resize Images on Mac [2025]: Complete Guide

Need to resize images on your Mac but not sure which method to use?

• Shrink photos for blog posts
• Optimize images for social media
• Reduce file size for email
• Batch resize hundreds of images

This article covers every method to resize images on Mac, from beginner-friendly to professional workflows. You'll find the right approach for your needs.

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Method 1: macOS Preview (Free)

The simplest method using Mac's built-in Preview app.

Resizing a Single Image

1. Double-click the image file to open in Preview
2. From the menu bar, select "Tools" → "Adjust Size..."
3. Enter width or height (pixels or percentage)
4. Ensure "Scale proportionally" is checked
5. Click "OK"
6. Command + S to save (or "Export As" for a new file)

Batch Resizing Multiple Images in Preview

Preview can resize multiple images, though it's somewhat tedious:

1. Select all images you want to resize
2. Right-click → "Open With" → "Preview"
3. In Preview, Command + A to select all in sidebar
4. "Tools" → "Adjust Size..."
5. Enter size and click "OK"
6. Command + S to save

Preview Limitations

• ❌ No preset saving - Enter size manually each time
• ❌ Large batches are tedious - 100+ images isn't practical
• ❌ No SNS size guidance - Research sizes yourself
• ❌ Can't output multiple sizes at once

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Method 2: Automator Shortcuts (Free)

macOS's built-in Automator lets you create right-click resize shortcuts.

Creating a Quick Action

1. Launch Automator (Spotlight search "Automator")
2. Click "New Document"
3. Select "Quick Action" and click "Choose"
4. In the search field, type "Scale Images"
5. Double-click "Scale Images" or drag it to the workflow
6. When asked "Will this change the original image files?" → Choose as needed
7. Set the size (e.g., 1200 pixels)
8. Command + S to save with a name (e.g., "Resize to 1200px")

Right-Click Resize from Finder

Your Quick Action is now available:

1. Select image(s) in Finder
2. Right-click → "Quick Actions" → Your action name

Images resize automatically.

Automator Limitations

• ❌ Complex setup - Challenging for beginners
• ❌ Multiple sizes difficult - Need separate actions per size
• ❌ SNS presets require manual creation
• ❌ No HEIC output support

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Method 3: Siri Shortcuts (macOS Monterey+)

macOS Monterey and later includes the Shortcuts app from iOS.

Creating an Image Resize Shortcut

1. Launch Shortcuts app
2. Click "+" to create new
3. Search for "Resize Image"
4. Drag "Resize Image" to add it
5. Set your size
6. Add "Save to Photo Album" or "Save File" action
7. Name and save your shortcut

Menu Bar Access

Enable "Pin in Menu Bar" in shortcut settings for quick access anytime.

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Method 4: Dedicated App (DockBuddy Resizer)

For batch resizing large numbers of images or daily resize tasks, a dedicated app is most efficient.

What is DockBuddy Resizer?

A resize-focused Mac app available on the Mac App Store. Drag and drop hundreds of images for batch processing in seconds.

Basic Operation

1. Launch DockBuddy Resizer
2. Drag & drop images into the window (multi-select OK)
3. Select a preset (or set size manually)
4. Resize complete

That's it. 100 images processed in about 10 seconds with drag and drop.

SNS Optimization Presets

Optimal sizes for each social platform are pre-registered:

Instagram

X (Twitter)

Facebook

Custom Presets

Save your commonly used size settings as presets for one-click application.

Supported Formats

HEIC images from iPhone work directly.

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Method Comparison Summary

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Frequently Asked Questions

Q: How do I resize HEIC files?

A: macOS Preview can open HEIC files, but saving in HEIC format requires a dedicated app like DockBuddy Resizer. Preview converts to JPEG on save.

Q: Does resizing reduce image quality?

A: For downsizing, proper quality settings prevent noticeable degradation. However:

• Upsizing causes quality loss - avoid it
• JPEG quality 80-90% is recommended (100% creates overly large files)

Q: How do I reduce file size?

A: To reduce image file size:

1. Reduce dimensions (pixels)
2. Lower JPEG quality (70-80%)
3. Convert PNG → JPEG (if transparency not needed)

Q: Can I convert to multiple sizes at once?

A: Difficult with Preview or Automator, but DockBuddy Resizer supports simultaneous multi-size output.

Q: How do I maintain aspect ratio?

A: All methods have a "maintain aspect ratio" or "scale proportionally" option—keep it enabled.

Q: Can I resize transparent PNGs?

A: Yes, transparency is preserved. However, choose PNG as output format. JPEG discards transparency.

Q: How do I batch process many images?

A: For dozens to hundreds of images, DockBuddy Resizer is most efficient. Preview and Automator work but take much longer.

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Recommendations by Scenario

Occasional Resizer (Few times per month)

→ Preview is sufficient

No additional apps needed—macOS built-in handles it.

Weekly Resizer

→ Create Automator shortcuts

Set up Quick Actions for common sizes for right-click convenience.

Daily Resizer / Batch Processing Needs

→ DockBuddy Resizer

• SNS managers
• E-commerce operators
• Photographers
• Designers

For these roles, batch processing hundreds of images in seconds with a dedicated app is the way to go. $9.99 one-time for dramatic time savings.

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Summary

Multiple methods exist to resize images on Mac, but the optimal choice depends on your needs:

If daily resizing is eating your time, investing in a dedicated app yields significant time savings.

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Related Articles

• App Icon Batch Generation Guide
• Image Resize Workflow for Designers & Photographers

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Try DockBuddy Resizer

Download Free

$9.99 one-time to eliminate image resizing hassles.