Photos and screenshots take up a lot of space on hard drives and cloud storage — in their unedited form, 5-6MB for an image file isn’t uncommon. If you’re trying to save space or just need to send smaller image files, you’ll want to compress them first. There are multiple ways to do shrink image files, and some will get the job done without even hurting the image quality that much. Here are a few ways to quickly do it on your Mac.
Lower the resolution to reduce the file size
You might already know this part, but the higher the image resolution of any given image, the larger the file size will be. You can reduce the file size quite a bit by reducing the resolution.
Depending on the image, taking a 4K file down to 720p or 1080p will not reduce the quality by much, but it will end up saving quite a lot of storage space. To do it, open the image in the Preview app and click Edit. Here, click Resize. Then, you can try out different resolutions and see how it affects the file size in the section below.
Export images in a lower quality
You can also use Preview to export lower-quality images, as long as you use the JPEG format. Open the image in Preview (this will work with multiple images as well), and go to File > Export. Here, choose the “JPEG” format, and reduce the Quality slider till you’re happy with the file size. Click Save.
Sometimes changing the file format can help
It’s not all about the image resolution — different file formats have different ways of storing data. For example, PNG is great for images with text in them, but if there are a lot of visuals and colours, the file size goes up a ton. Sometimes, simply changing the file format to JPEG can save up to 90% storage space with almost no loss in quality.
You can use Preview’s Export tool to export the image in a different format. Go to File > Export and choose JPEG in the Format section. If you’re using macOS Monterey and higher, you can use do this from Finder itself. Select the images that you want to convert, right-click, and go to Quick Actions > Convert Image. Here, switch to a format like JPEG. To reduce the file size further, you can choose between Small, Medium, and Large file sizes.
Batch compress images on your Mac using ImageOptim
If your work calls on compressing images left and right, it’s best to use a dedicated tool like ImageOptim. It’s a free, open-source app dedicated to compressing images so that they can be easily used on the web.
It removes unnecessary metadata and compresses images without losing out on image quality. It’s also pretty easy to use. Just drag in the images, and ImageOptim will do the rest.
Aggressively compress images online using TinyPNG
While ImageOptim is a great native tool for compressing images, it can sometimes be hit-and-miss based on the images you’re feeding in.
If you’re looking for a really aggressive method for compressing images, use the free online service called TinyPNG. You can compress images in multiple formats (PNG, JPEG, and WebP), and sometimes you can compress PNG files by 90%.
The only downside is that you need to upload and download images manually from the website, and the free version only lets you batch process 20 images at a time. The $35/year Pro subscription removes all the limits.