Resizing images one at a time in Preview gets tedious quickly. Whether you are preparing images for a website, compressing photos to send by email, or standardising dimensions for a project, batch resizing saves a significant amount of time.
macOS offers built-in options through Preview and Automator. For larger batches and more control, ImageZero handles hundreds of images at once with a preview of the output before you commit.
Method 1: Batch Resize in Preview
Preview, macOS's built-in image viewer, can resize multiple images at once:
- Select all the images you want to resize in Finder.
- Right-click and choose Open With → Preview.
- In Preview, press Command + A to select all images in the sidebar.
- Go to Tools → Adjust Size…
- Enter the new dimensions (width, height, or percentage).
- Check Scale proportionally to maintain the aspect ratio.
- Click OK.
- Save all files: File → Save All (or Command + Option + S).
Limitation: Preview's batch resize saves to the same file format and location. If you want to resize and convert, or save to a different folder, you need Automator or a dedicated app.
Method 2: Automator Batch Resize
Automator can build a resize workflow that saves copies to a new folder:
- Open Automator (in Applications).
- Create a new Workflow or Quick Action.
- Add the Scale Images action (search for it in the library).
- Before Scale Images, add Copy Finder Items to specify an output folder — this prevents overwriting your originals.
- Configure the scale action with your target size.
- Run the workflow on your selected images.
Automator is free and more flexible than Preview, but it takes time to set up the workflow correctly.
Method 3: ImageZero (Recommended for Regular Use)
ImageZero is designed for exactly this task. It handles batch resize, format conversion, and compression in one window with a live preview.
Supported input formats: JPG, JPEG, PNG, HEIC, WebP Supported output formats: JPG, PNG, WebP
How to batch resize with ImageZero:
- Open ImageZero.
- Drag in your images (or a folder of images).
- Enable the Resize toggle.
- Choose your resize method:
- By width — set a specific pixel width; height adjusts automatically
- By height — set a specific pixel height; width adjusts automatically
- By percentage — reduce to 50%, 75%, etc. of the original size
- Custom dimensions — set both width and height exactly
- Check the preview to see the output dimensions for each image.
- Click Export. All resized images are saved to your chosen output folder.
ImageZero can combine resize with compression and format conversion in one pass — useful when you want to resize and convert HEIC photos to JPG at the same time. See how to convert HEIC to JPEG on Mac.
The free tier processes up to 10 images per session. A Pro license removes all limits.
What Resize Mode Should You Use?
| Goal | Recommended resize mode |
|---|---|
| Fit images into a max width (blog images, email) | By Width |
| Thumbnail grid with consistent height | By Height |
| Make all images half-size | By Percentage (50%) |
| Exact dimensions for a design spec | Custom dimensions |
Resize Without Distortion
Always check Maintain aspect ratio (or the equivalent in your tool). Resizing to exact dimensions without maintaining aspect ratio will stretch or squash the image. If you need to fit into a fixed box, consider cropping rather than resizing.
FAQ
Does resizing reduce image quality? Reducing an image's dimensions reduces file size and, when enlarging beyond the original size, reduces quality. Resizing down from a high-resolution original to a web-appropriate size has minimal visible quality impact.
Can I resize images without losing the original? Yes. ImageZero always saves to a new file — originals are never overwritten. Preview requires care: use Export rather than Save to keep originals intact.
How do I resize for a specific website? Check the platform's recommended image dimensions. Common sizes: 1200px wide for blog posts, 800×800px for product images, 1080×1080px for Instagram. Use ImageZero's custom dimensions option for these.
Can I batch resize images in different formats at once? Yes. ImageZero accepts mixed input — you can drop in JPG, PNG, and HEIC files together and resize them all in one pass.
Summary
For occasional one-off resizing, macOS Preview works fine. For regular batch work, ImageZero is faster and more flexible — add your files, choose your resize settings, preview the output, and export everything in one step. Originals are never touched.
Also see: Convert HEIC to JPEG on Mac without iCloud and explore the Images category for more image guides.