pngCrushrrr is described as 'Drag your PNGs onto PNGCrushrrr and get super-optimized files ready to be emailed or posted on the web! Supports one or more files being dropped and instead of overwriting your original files, PNGCrushrrr outputs .crushed.png files for comparison' and is an app in the Photos & Graphics category. There are more than 50 alternatives to pngCrushrrr for a variety of platforms, including Windows, Mac, Online / Web-based, Linux and Wordpress. The best alternative is Caesium Image Compressor, which is both free and Open Source. Other great apps like pngCrushrrr are ImageOptim (Free Personal, Open Source), RIOT - Radical Image Optimization Tool (Free), XnConvert (Free Personal) and TinyPNG (Freemium).
Caesium Image Compressor lets you compress your pictures up to 90% without visible quality loss. Providing a simple yet effective interface with a real-time preview and multiple image processing at the same time, everyone will be able to reach the best result.
ImageOptim is excellent for publishing images on the web (easily shrinks images “Saved for Web” in Photoshop). It's useful for making Mac and iPhone/iPad applications smaller (if you configure Xcode to allow better optimization).
Saving images for web/email/other media with the best compression ratio and quality is a difficult task if you don’t have the right tools. Choosing the right format then choosing the right parameters are the key factors of smaller files.
XnConvert is an easy image converter for graphic files, photos and images available on Windows, MacOSX and Linux. It supports more than 400 file formats (jpeg, tiff, png, gif, camera raw, jpeg2000, WebP, OpenEXR, ...).
TinyPNG uses smart lossy compression techniques to reduce the file size of your PNG files. By selectively decreasing the number of colours in the image, fewer bytes are required to store the data. The effect is nearly invisible but it makes a very large difference in file size!
Experimental, fast Web PNG/JPG optimizer which offer lossless, visually lossless or lossy compression. it performs image reductions over iterations thanks to recursive multi-processing and multithreading systems.