Optimising images has become crucial for various reasons, from improving website performance to conserving storage space. Whether you're a web developer aiming for faster page loads or an everyday user looking to save storage, keep on reading this guide that explores the ins and outs of PNG compression, offering insights into techniques, tools, and best practices.

By the end of it, you'll be equipped with the knowledge to reduce PNG file sizes without compromising image quality. But first, let’s define what a PNG file is.

What Is a PNG Image file?

A PNG (Portable Network Graphics) file is a raster graphics file format that uses lossless data compression. It was designed to replace the older GIF (Graphics Interchange Format) and TIFF (Tagged Image File Format) formats for online use. PNG is well-suited for web graphics and supports transparent backgrounds.

Key features of PNG files include:

Lossless compression: PNG uses lossless compression, meaning that the image quality is not compromised during compression. This is in contrast to lossy compression formats like JPEG, which sacrifice some image information to achieve higher compression.
Transparency: PNG supports alpha channel transparency, allowing parts of the image to be fully or partially transparent. This is useful for creating images with irregular shapes that can blend seamlessly with any background.
Colour depth: PNG supports various colour depths, including grayscale and true colour (24-bit). It also supports indexed colour, making it suitable for a wide range of applications.
Metadata: PNG files can store additional information, such as textual information and copyright details, in the form of metadata.
Wide support: PNG is widely supported by web browsers and graphic software, making it a popular choice for images on the internet.

While PNG is versatile and widely used, it's worth noting that it may result in larger file sizes compared to highly compressed formats like JPEG. The choice of image format depends on the specific requirements of the project, considering factors such as image quality, transparency, and file size constraints.

Why You Might Need to Compress a PNG Image

PNG files, especially those with intricate details or large dimensions, can occupy significant storage space, and compression helps reduce the file size, making it more storage-efficient without compromising the overall image quality. On the web, large PNG files can result in slower loading times for web pages. So, to make a page load faster, compressing PNG comes in handy, improving the overall user experience, particularly for users with slower internet connections.

In situations where bandwidth is a concern, such as mobile networks or limited data plans, compressed PNG images can help minimise data usage without sacrificing image clarity. Needless to say, smaller file sizes are easier to share, whether through email, messaging apps, or other platforms, such as Instagram or Facebook. Compressing PNG images makes them more manageable for distribution without compromising their visual integrity.

Note, however, that while compression reduces file size, the extent to which it can be applied depends on the specific requirements of the project. Balancing file size reduction with the need for image clarity is crucial to ensure that the compressed PNG still meets the intended visual standards.

How to Compress a PNG Image: 4 Ways

PNG files are known for their high quality, making them a popular choice for clear and crisp images. However, in some cases, it might be necessary to compress PNG file sizes to save storage space while maintaining the image dimensions. How? Let’s find out.

How to Optimise a PNG File with 4K Image Compressor

4K Image Compressor is a desktop app compatible with Windows, macOS, and Linux computers. Apart from PNG, it can optimise images in various formats, including WEBP, HEIC, and JPEG, but more formats, such as PDF, will be available soon. What's more, you can compress multiple images at a time with no need to upload every image one by one.

If you want to reduce the size of your PNG image, you can easily do it with 4K Image Compressor. Here’s how:

1. Launch 4K Image Compressor.

2. Select the output format and value in the settings bar.

3. If you selected the Percent value, enter the number of percents you want to compress the file by. If you selected the Size value, enter the number and unit (B, KB, MB).

4. Click the Compress button located in the middle of the application window.

5. In the opened window, select the image for compression and click Open.

Your PNG will be immediately uploaded and compressed.

Hover the cursor over the compressed image preview and click the folder icon to find the file on your computer.

Tip: You can also choose the compression presets if you choose the auto compression.

How to Reduce a PNG File Size in Photoshop

Compressing a PNG in Photoshop is a bit more complicated, but if you’re an avid Photoshop user and generally tech-savvy, you can try this method as well. To reduce the file size of a PNG in Photoshop, follow these steps:

Open the PNG file in Adobe Photoshop by dragging and dropping the image into the application or using File -> Open.
Navigate to Image -> Image Size or press Ctrl+Alt+I.
In the Image Size Dialog box, decrease the Height/Width of the image to compress its size. Ensure that the option to constrain proportions is selected.
Click on the Resample button and choose Bicubic Sharper from the list to maintain image sharpness during compression.
Click OK to close the Image Size dialog box and save the compressed image.

How to Compress a PNG Image Online

In addition to desktop third-party software, there are plenty of online solutions that can be just as helpful. Here are a few.

TinyPNG

With today's advanced technology, file compression tools leverage high-end algorithms to minimise PNG file sizes while preserving image quality. Here are the steps to compressing PNG file sizes using the online compression tool provided by TinyPNG.

TinyPNG is a popular online tool that uses smart lossy compression techniques to reduce PNG file sizes while preserving image quality. You can visit their website, upload your PNG files, and download the compressed versions.

Open the TinyIMG PNG compressor in your web browser.
Drag and drop the PNG files you wish to reduce in size. The tool allows you to upload up to 20 images simultaneously for bulk compression, with each file size not exceeding 5MB.
Once the compression process is complete, the compressed PNG file becomes available for download.
Before downloading, you can compare the file sizes of the original and compressed images, observing the reduction achieved.

Compressor.io

Compressor.io is also an online tool that supports various image formats, including PNG. It uses different compression algorithms to reduce file sizes. Users can upload images, compress them, and download the optimised files.

Here are the steps for compressing a PNG image using Compressor.io:

Go to the Compressor.io website by typing "compressor.io" in your web browser.
Click on the "Select files" button or drag and drop your PNG file directly onto the webpage.

Compressor.io may offer some optional settings depending on the file type. For PNG files, it typically provides options for lossless and lossy compression. You can choose your preferred compression level based on your quality requirements.

After uploading the PNG file and adjusting settings (if necessary), click on the "Apply Compression" or similar button to start the compression process.

Compressor.io will process the image, and you'll see a progress indicator. The time required for compression depends on the file size and your internet connection speed.

Once the compression is complete, a download link or button will appear. Click on it to download the compressed PNG file to your computer.
Save the compressed PNG file to your preferred location on your computer.

Compressor.io makes the optimisation process user-friendly with a simple interface. Just follow these steps, and you'll be able to reduce the size of your PNG images while maintaining a satisfactory level of quality.

There are also online tools that work absolutely the same:

ImageOptim: ImageOptim is both an online tool and standalone software (for Mac) that focuses on lossless image compression. It supports various image formats, including PNG. Users can upload images online or use the software to compress files locally.
OptiPNG: OptiPNG is an online service that specialises in optimising PNG files. It allows you to upload your PNG images, optimise them, and download the compressed versions.
JPEG-Optimizer: While primarily designed for JPEG optimiыation, JPEG-Optimizer also supports PNG files. Users can upload PNG images, adjust compression settings, and download the optimised files.

How to make a PNG smaller without losing quality?

Basically, 4K Image Compressor doesn’t ruin quality when optimising images; not just PNG but other formats, too. We tested online compressors, too, but the results were quite inconsistent.

Can I reduce a PNG file size on a Mac?

Sure! All the tools we featured above, including our own 4K Image Compressor, run on Mac. Online tools are, of course, available on every OS.

Compressing a PNG Image: Bottom Up

Choose the method that best fits your needs and preferences. Keep in mind that while compression reduces file size, it may also impact image quality to some extent. Finding the right balance between size reduction and maintaining acceptable image quality is crucial for achieving the desired results.