You’ve probably been there. You spend hours designing a pixel-perfect graphic or taking a high-res screenshot, only to realize the file size is absolutely massive. It’s 5MB. Maybe 10MB. You try to upload it to your website or send it over Discord, and it just hangs. Or worse, it tanks your PageSpeed Insights score into the red. It's frustrating because PNGs are supposed to be the "good" format. They handle transparency. They don't have those gross blurry artifacts you see in JPEGs. But that quality comes at a literal cost in bytes.
Actually, the secret to how to compress a PNG isn't just about making it smaller; it’s about understanding why it’s so big in the first place. PNG stands for Portable Network Graphics. It’s a lossless format. This means when you save it, the computer keeps every single bit of data. While that’s great for archives, it’s overkill for the web. Most of that data is invisible to the human eye. We’re going to look at how to strip away the junk without making your image look like a muddy mess from 1998.
Why your PNG files are secretly bloated
The technical reason is deep. PNG uses the DEFLATE compression algorithm, which is basically the same thing used in ZIP files. It looks for patterns. If you have a solid blue sky, it says "okay, the next 500 pixels are this specific shade of blue" instead of listing every pixel individually.
But here is the kicker: PNG-24 is the standard most people use. It supports over 16 million colors. Do you really need 16 million colors for a logo with three shades of green? Probably not. When you have a massive color palette, the "patterns" the algorithm looks for become much harder to find. This leads to those chunky file sizes that make mobile users want to throw their phones across the room.
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I’ve seen developers leave metadata in their images too. Things like the date the photo was taken, the GPS coordinates, or the version of Adobe Photoshop used. That's just dead weight. It adds up. Honestly, if you aren't stripping that stuff out, you're just wasting bandwidth.
The difference between Lossy and Lossless (And why you care)
People get weirdly defensive about lossless compression. They think if they touch a single pixel, the image is ruined. That’s just not how it works in the real world.
Lossless compression, like what you get with tools like OptiPNG or PNGOUT, is basically just "re-arranging" the furniture. It finds a more efficient way to store the exact same pixel data. You’ll save maybe 5% to 10% on a good day. It’s safe, sure, but it's rarely enough to satisfy a Google Core Web Vitals report.
Then there is Lossy compression. This is the magic stuff. Tools like TinyPNG or ImageOptim use a process called "quantization." They look at those 16 million colors and realize that 50 of them are so similar that the human eye can't tell them apart. It merges them. Suddenly, the patterns are way easier for the computer to see. You can often drop a file size by 70% or 80% without any noticeable drop in quality. It’s wild. If you’re wondering how to compress a PNG for a portfolio or a blog, this is almost always the route you should take.
When to stay lossless
- You are doing high-end print work.
- You need to edit the file again later and don't want "generation loss."
- You're dealing with medical imaging or scientific data where every pixel is a data point.
Tools that actually work (No fluff)
I've tried basically every tool on the market. Some are great. Some are garbage.
TinyPNG (Web-based)
This is the gold standard for most people. It’s easy. You drag. You drop. You download. They use a smart lossy technique that converts your PNG-24 files into much smaller 8-bit indexed color files. The transparency stays intact, which is the main reason we use PNG anyway. They have a developer API too, which is handy if you’re trying to automate things.
ImageOptim (Mac App)
If you’re on a Mac, just get this. It’s free. It’s open source. It’s a "wrapper" that runs several different compression engines (like AdvPNG and Pngcrush) all at once. It’s great because it’s "drag and drop" but works locally on your machine, so you aren't uploading sensitive company assets to a random server.
Squoosh.app (Browser-based)
This is a Google Chrome Labs project. It is incredible. It lets you see a side-by-side comparison in real-time. You move a slider and see exactly where the "cracks" start to show in the image quality. It gives you total control over the "effort" the compressor puts in. If you want to know exactly how to compress a PNG to a specific kilobyte limit, this is the tool.
Command Line (For the nerds)
If you’re comfortable with a terminal, pngquant is the engine that powers a lot of these other apps. Running a simple command like pngquant --quality=65-80 image.png can give you instant results across an entire folder of assets. It's fast. It's efficient. It's what the pros use.
The "Invisible" problem with screenshots
Windows and macOS both love saving screenshots as PNGs. On a Retina display or a 4K monitor, a simple screenshot of a spreadsheet can be 3MB. Why? Because it’s capturing every single sub-pixel.
Most people just take that file and upload it. Stop doing that.
Before you even think about how to compress a PNG, ask yourself if it needs to be a PNG. If it's a photo of a sunset, it should be a JPEG or a WebP. If it's a screenshot of a website with lots of text and solid colors, PNG is fine, but you have to run it through a compressor first. macOS screenshots are notoriously "fat" because they include an alpha channel (transparency) for the window shadows. You can actually turn that off in the terminal if you want to save space at the source, but that's a whole other rabbit hole.
What about WebP? The elephant in the room.
We have to talk about WebP. Google pushed it hard, and now it’s pretty much supported everywhere. WebP can do everything PNG can do—transparency, lossless, lossy—but it does it better. Usually, a WebP version of a PNG will be 25% to 35% smaller right out of the gate.
However, PNG is still the king of compatibility. If you're sending an image to a client who might open it in an old version of Word, or if you're working in certain email environments, WebP might break. That's why knowing how to compress a PNG is still a vital skill in 2026. You need that fallback.
Steps to a perfect compression workflow
Don't just randomly click buttons. Have a system.
- Export at the right size. If your blog is 800 pixels wide, don't upload a 4000-pixel wide PNG. Resize it first. This is the biggest mistake people make.
- Choose your weapon. For one-off images, use Squoosh or TinyPNG. For folders, use ImageOptim or a CLI tool.
- Check the transparency. Sometimes aggressive compression can create "halos" around transparent edges. Look closely at the borders.
- Strip Metadata. Ensure your tool is removing EXIF data. You don't need your camera's serial number embedded in a "Contact Us" button icon.
- Test. Put the compressed image on a background that isn't white. See if it still looks clean.
Common myths about PNG compression
I hear people say that "re-compressing a PNG ruins it." Not necessarily. If you use lossless compression, you can do it a thousand times and the image will stay identical. If you use lossy, yes, you'll eventually see "artifacts" (those weird blocks and smudges). But honestly, most people are too scared of lossy. Try it. You’ll be surprised how much you can get away with.
Another myth: "Interlaced PNGs are better." No. Just no. Interlacing makes the image appear to load "blurry" and then get sharper, rather than loading from top to bottom. It actually increases the file size because it breaks up the patterns that the DEFLATE algorithm relies on. Unless you're back in the days of 56k dial-up, don't use interlacing.
Real-world impact of smaller images
Think about a mobile user on a spotty 4G connection in a tunnel. If your page has five uncompressed 2MB PNGs, that’s 10MB of data just for images. That page might take 15 seconds to load. According to Google’s own data, most people bounce after 3 seconds.
By learning how to compress a PNG, you aren't just saving disk space. You are literally making more money by keeping people on your site. You're improving your SEO. You're making the internet a slightly less bloated place. It seems like a small thing, but it’s one of those "marginal gains" that adds up to a massive advantage over time.
Actionable Next Steps
To get started right now, take the largest PNG on your desktop and run it through Squoosh.app.
Compare the original to a version where you’ve reduced the palette to 128 or even 64 colors. Look at the file size difference. Usually, it’s staggering. Once you see it, you can't un-see it. You'll start noticing bloat everywhere.
Next, audit your website. Use a tool like Lighthouse (built into Chrome DevTools) to find every image that is oversized. Download them, run them through a batch compressor like ImageOptim, and re-upload. It’s a boring Saturday afternoon task, but your search rankings will thank you for it.
Finally, if you’re a designer, check your export settings in Figma or Adobe XD. Often, they have plugins that handle compression automatically so you don't even have to think about it. Automating the "how to compress a PNG" part of your workflow is the ultimate goal. Stop doing it manually and let the algorithms do the heavy lifting.