Most people have used the internet to share an image at some point. Whether it was a selfie, a photo of an adorable pet, a gorgeous landscape, or just a funny meme, images are great for communication on the internet.
One of the problems that you may run into when trying to share an image, is file size. Many websites or apps restrict the size of images that you’re allowed to upload. This makes sense from their perspective because they would likely have to host every large image file uploaded for a long time, something that would likely increase the size of backups and require more and more storage space. Unfortunately, the way it’s handled in pretty much every app isn’t great from a user perspective.
Most users when they see that their image was rejected for being too big, may try sending it on another platform, but will likely just give up. With a small amount of image processing, however, it should be easy to be able to upload a reasonably high-quality image.
There are two techniques used to reduce image file size. The first is downscaling, which just involves reducing the dimensions of an image. For example, reducing a 4K image to 1080p should roughly cut the image file size to a quarter of what it was. The other method is to compress the image. Image compression uses advanced techniques to minimise the amount of data required to represent the image. There are two classes of compression algorithm, lossless and lossy. Lossless compression makes reasonable reductions in file sizes while maintains full image quality. Lossy compression can reduce the file size even further but results in a loss of image quality. With careful optimisation, the quality loss of lossy image compression can be almost imperceptible.
Ideally, if you tried to upload an image that was too big, a website or app, would instead choose to generate a compressed version on the fly, and save that instead. Unfortunately, most sites don’t do this and just throw an error instead. If you encounter this though, instead of giving up, you can compress the image yourself and then upload the compressed image.
Compressing images on your computer
A simple way to compress an image is to try changing the file format. For example, PNG uses lossless compression, while JPG uses a lossy format. Generally, if you open a PNG image and then re-save it as a JPG, the resulting image file size is smaller. Any sort of image editor should be able to save an image in a new format.
Tip: While you’re saving in a different image format, you could also try reducing the dimensions of the image too. Reductions in image dimensions make a big difference to file size when the image is particularly large.
Many image formats support different levels of compression. When saving an image in an image editor, check to see if there is a “quality” or “compression” option that you could adjust. This can make a big difference to the file size, but also to the image quality.
Compress images online
There are a number of online tools that can compress images for you. If you want to try these, we recommend Compressor.io and Squoosh.
Compressor.io allows you to upload images up to 10MB in size, it will then compress them, show you the file size reduction and offer you a download link. You can also choose to compare the before and after pictures if you want to check for any loss in quality. The main downsides with this app are the 10MB size limit and the fact that you’re uploading the image to a third-party website, which isn’t great for potentially sensitive images.
Squoosh is a Google-owned tool, which doesn’t bode too well for privacy, however, it doesn’t actually upload your image at all. Instead, it loads the image you select into your browser and performs all processing directly on your computer. This means that there’s no file size limit or privacy concerns over sensitive images.
In Squoosh you can select which image compression algorithm you want to use and configure its settings all while using a live before and after comparison. Once your computer has completed any processing it needs to perform it will show the image file size comparison and give you the option to download it. This process offers a lot more depth than Compressor does, but this can also result in it taking longer as you fiddle with the settings to get it perfect.
