Whether you’re a photographer processing hundreds of RAW files, a web developer optimizing images for a website, or someone who just needs to convert a folder of images to a different format, batch conversion can save you hours of manual work.

Method 1: Using macOS Preview (Built-in)

Step-by-Step Instructions

  1. Select your images: In Finder, select all the images you want to convert by clicking the first image, then holding Shift and clicking the last image.
  2. Open in Preview: Right-click and choose “Open With” → “Preview”
  3. Select all in Preview: Press Cmd+A to select all images in the sidebar
  4. Export: Go to File → Export Selected Images…
  5. Choose format: In the dialog, select your desired format (JPEG, PNG, TIFF, etc.)
  6. Set quality: Adjust quality settings if available
  7. Export: Choose destination folder and click “Choose”

✅ Pros: Free, built-in, no installation required ❌ Cons: Limited format support, basic options only

Method 2: Using Automator (Advanced Built-in)

Creating a Reusable Workflow

  1. Open Automator: Find it in Applications or use Spotlight search
  2. Create new workflow: Choose “Workflow” when prompted
  3. Add “Get Selected Finder Items”: Drag this action from the library
  4. Add “Change Type of Images”: Search for this action and drag it below the first one
  5. Configure format: Choose your target format (JPEG, PNG, TIFF, etc.)
  6. Save workflow: File → Save and give it a descriptive name
  7. Use it: Select images in Finder, right-click → Services → Your Workflow Name

Method 3: Using Command Line (Terminal)

Using ImageMagick

# Install ImageMagick via Homebrew
brew install imagemagick

# Convert all JPEG files to PNG
magick *.jpg -format png -path ./converted %t.png

# Resize and convert
magick *.jpg -resize 800x600 -format webp ./converted/%t.webp

⚡ Pros: Very powerful, scriptable, supports all formats ⚠️ Cons: Command line only, steep learning curve

Method 4: Using Dedicated Apps

Why choose a dedicated app?

✅ Advantages

  • User-friendly interface
  • More format options
  • Advanced compression settings
  • Batch processing features
  • Preview capabilities
  • Metadata management

Popular Options

  • Picmal - Privacy-focused, native macOS
  • ImageOptim - Web optimization focus
  • Squash - Simple compression tool
  • BRAW Toolbox - Professional video/RAW

Choosing the Right Method

Decision Matrix

🆓 Occasional Use (< 50 images/month) Use macOS Preview - it’s free and handles basic conversions well

🔄 Regular Use (50-500 images/month) Consider Automator workflows or a dedicated app like Picmal for better efficiency

🏢 Professional Use (500+ images/month) Invest in professional tools or learn command line for maximum control and speed

Best Practices

  • Always backup originals: Keep a copy of your source files before batch converting
  • Test with a small batch first: Verify settings work correctly before processing hundreds of files
  • Use descriptive naming: Add prefixes or suffixes to distinguish converted files
  • Consider organization: Create separate folders for different formats or purposes
  • Monitor quality: Check a few converted images to ensure quality meets your needs