ImageAlpha is a Mac app that compresses PNG images with transparency by converting them from 24-bit to optimized 8-bit palettes. It reduces file sizes by 60-80% while preserving alpha channels and visual quality. Web designers use it to shrink illustrations, UI graphics, and icons for faster page loads without switching to lossy JPEGs that don’t support transparency.

Key Specs

Price	Free (open-source, GPL v2)
Platform	Mac only
Best for	Compressing PNGs with transparency for web use
Learning curve	2 minutes (drag and drop interface)

How Designers Use ImageAlpha

ImageAlpha fits into web optimization workflows where PNG file sizes hurt page performance.

For Web Graphics and Illustrations

Export illustrations from Illustrator or Figma as 24-bit PNGs with transparency, then drag them into ImageAlpha. Adjust the quality slider (60-80% is usually imperceptible) and save. The resulting PNG8+alpha files load 3-5x faster on web pages while maintaining transparency for overlays and layered designs. This is crucial for hero graphics, decorative elements, and marketing pages where every kilobyte counts.

For App UI Assets

Designers compress icon sets and UI graphics for mobile apps and web apps. ImageAlpha reduces asset bundles without requiring lossy JPEG conversion. The transparency is preserved, so buttons, badges, and overlays still work against any background. Combine with Xcode’s asset catalog or React Native’s image pipeline for optimized app packages.

For Batch Processing Design Exports

After exporting dozens of graphics from design tools, drag the entire folder into ImageAlpha for batch processing. It compresses all PNGs while preserving directory structure. For automated workflows, use the underlying pngquant command-line tool in npm scripts, Gulp tasks, or CI/CD pipelines. This ensures every deployed image is optimized.

ImageAlpha vs. Alternatives

How does ImageAlpha compare to other PNG compression tools?

Feature	ImageAlpha	TinyPNG	ImageOptim	pngquant CLI
Price	Free	Free (limited)	Free	Free
Platform	Mac only	Web-based	Mac only	Cross-platform
Compression	Lossy (high)	Lossy (high)	Lossless	Lossy (high)
Batch processing	✅ Yes	⚠️ Limited free tier	✅ Yes	✅ Via scripting
Quality control	✅ Slider	❌ Automatic	❌ Automatic	✅ Flags
Automation	⚠️ Via CLI	✅ API available	❌ GUI only	✅ Build scripts
File size reduction	60-80%	60-80%	10-30%	60-80%

Choose ImageAlpha if: You’re on Mac, need offline compression with quality control, and want a simple drag-and-drop app.

Choose TinyPNG if: You need quick web-based compression without installing software, or you’re on Windows/Linux.

Choose ImageOptim if: You need lossless compression that preserves every pixel, or you want to optimize JPEGs and GIFs alongside PNGs.

Choose pngquant CLI if: You’re automating image optimization in build pipelines, npm scripts, or CI/CD workflows.

Getting Started with ImageAlpha

A 5-minute workflow to compress PNGs:

Step 1: Drag PNGs into ImageAlpha

Export your graphics as 24-bit PNGs from Figma, Illustrator, or Photoshop. Open ImageAlpha and drag the files (or a folder) into the window. The app shows before/after previews with file size comparisons.

Step 2: Adjust quality slider

Move the quality slider (right panel) between 60-90%. Watch the preview update in real-time. Look for artifacts or banding in gradients. Most illustrations look perfect at 70-80% quality while saving 70% file size. Flat graphics with few colors can go lower (40-60%).

Step 3: Save optimized PNGs

Click “Save” for each image, or use “Save All” for batch processing. ImageAlpha exports PNG8+alpha files that work in all modern browsers (including IE6, if you care). The files are 60-80% smaller than the originals with transparency intact.

ImageAlpha in Your Design Workflow

ImageAlpha slots into the export and optimization stage of web design.

• Before ImageAlpha: Design in Figma/Sketch, export graphics as high-quality PNGs with transparency
• During ImageAlpha: Drag exported PNGs into app, adjust quality, batch compress
• After ImageAlpha: Upload optimized PNGs to web server, use in HTML/CSS, measure page load improvements

Common tool pairings:

• ImageAlpha + ImageOptim for double compression (lossy with ImageAlpha, then lossless with ImageOptim)
• ImageAlpha + Figma for exporting illustrations and immediately compressing for web deployment
• pngquant (CLI) + Webpack for automated image optimization in JavaScript build pipelines
• ImageAlpha + SVGO for comparing PNG compression vs SVG file sizes to choose the best format

Common Problems (and How to Fix Them)

These issues come up when compressing PNGs with ImageAlpha.

“The compressed image has visible banding or artifacts”

You’ve set the quality too low for that image. Gradients and photos need higher quality settings (80-90%) than flat illustrations (40-70%). Increase the slider until artifacts disappear. If the file size is still too large at high quality, consider converting to JPEG (if transparency isn’t needed) or SVG (if it’s vector-based).

“ImageAlpha doesn’t compress my PNG much”

Your PNG might already be 8-bit, or it has very few colors. ImageAlpha excels at compressing 24-bit PNGs with lots of colors. Check your original file: if it’s already optimized or uses a limited palette, there’s little room for compression. Try ImageOptim for lossless optimization instead.

“The app says it can’t compress this image”

ImageAlpha only works on PNG files with alpha channels (transparency). If your PNG is fully opaque, convert it to JPEG (smaller file size) or use ImageOptim for lossless PNG optimization. ImageAlpha skips images it can’t improve.

“I need to automate this for hundreds of images”

Use pngquant from the command line. It’s included in ImageAlpha’s app bundle at ImageAlpha.app/Contents/Resources/pngquant. Run it in terminal: pngquant --quality=65-80 --ext=.png --force *.png. Integrate it into npm scripts, Gulp, Webpack, or CI/CD pipelines for automated compression on every build.

“Does this work on Windows or Linux?”

No. ImageAlpha is Mac-only. Use TinyPNG (web-based), pngquant CLI (cross-platform), or Squoosh (web-based) on Windows and Linux. The pngquant command-line tool offers the same compression algorithm on any platform.

Frequently Asked Questions

The Mac app has limited recent development (last major updates were several years ago), but the underlying pngquant tool it’s based on is actively maintained. ImageAlpha still works on modern Macs and remains effective for PNG compression, though newer web workflows often use command-line tools or build pipelines.

Yes. ImageAlpha is free, open-source software under GPL v2. You can download it from pngmini.com at no cost. There are no premium features or paid upgrades.

Choose ImageAlpha if you’re on Mac, need offline compression, want full control over quality settings, and work with batches locally. Choose TinyPNG if you need quick web-based compression, compress a few images occasionally, or work on Windows/Linux without installing software.

Yes, but visually imperceptible. ImageAlpha uses lossy compression, converting 24-bit PNGs to 8-bit with optimized palettes. You control the quality slider (1-100). At 60-80%, most images look identical to the original while saving 60-80% file size. The transparency channel is preserved.

Yes. Drag multiple PNG files or folders into ImageAlpha and it processes them in batch. For larger batches or automation, use the command-line pngquant tool (included in ImageAlpha’s app bundle) in build scripts or npm workflows.

ImageAlpha uses lossy compression, reducing colors to save more space (60-80% smaller files). ImageOptim uses lossless compression, keeping all original data (10-30% smaller files). Use ImageAlpha when file size matters most, ImageOptim when you need pixel-perfect originals. Many designers use both: ImageAlpha first, then ImageOptim on the result.