How to Compress PNG Files Without Losing Transparency
PNG is the format you reach for when an image has to sit on top of something else — a logo over a coloured header, a product cut-out, a screenshot with a soft shadow. It is also the format that quietly turns a simple graphic into a two-megabyte page-weight problem. A good PNG compressor fixes that without flattening the transparent edges you chose PNG for in the first place. This guide covers how to compress PNG files properly, what each mode actually changes, and what to do when you need to reduce PNG file size down to a particular number.
1. Why Your PNG File Is So Large
People are often surprised that a plain logo weighs more than a detailed photograph. The reason is that PNG is a lossless format by design. As the W3C Portable Network Graphics specification sets out, the format stores an exact record of every pixel, plus an optional alpha channel that records how transparent each of those pixels is. Nothing is thrown away, ever. That fidelity is the whole point of PNG, and it is also the whole reason your file is big.
Two things drive the size up more than anything else. The first is the number of distinct colours in the image: a screenshot with a gradient, a drop shadow or a photographic element contains thousands of near-identical shades that the format has to describe individually. The second is transparency, because every pixel now carries a fourth value alongside its red, green and blue. Export a 3000-pixel-wide banner with a soft transparent fade and a large PNG file of several megabytes is the ordinary result rather than the exception.
So when people look for a way to make a PNG smaller, what they are really asking is how to reduce that colour variety without anyone noticing. The three modes on the tool above are three answers to the question “how much are you willing to give up?”
2. How to Compress a PNG Online Free (Step-by-Step)
There is no account, no email and no trial period. Using the PNG optimiser above to compress PNG online free takes three steps:
Add your PNG
Drag a .png onto the panel above or click to browse. Only PNG files are accepted — anything else is turned away with a plain message rather than a silent failure — and the original file size is shown as soon as it loads.
Pick a compression mode
Choose Lossless, Balanced or Maximum Shrink. Balanced is the recommended default and is the right answer for most logos, icons, screenshots and web graphics.
Download the smaller file
Press compress. The download button shows the new file size and the percentage saved, and the file arrives named after your original with -min added.
That is the whole workflow to shrink a PNG file. You can change your mind freely: pick a different mode and compress the same image again. Nothing is queued, nothing is watermarked, and the output is a normal .png that opens anywhere a PNG opens — on a phone as happily as on a laptop, with nothing to install.
3. Lossless, Balanced or Maximum Shrink: Which Mode to Use
The three buttons are the only decision you have to make, and the difference between them is simply how much colour detail each one is allowed to simplify.
Lossless
Every pixel comes through untouched. This is the mode for photographs, artwork, medical or legal imagery, and anything you will edit again later. Because nothing is simplified, the savings are the most modest of the three — and if a rewrite would produce a bigger file than you started with, you get your original size back instead. You never leave with a larger file than you arrived with.
Balanced
Colour values are snapped onto a coarser ladder, which removes the near-duplicate shades that inflate a file without contributing anything you can see. This is the recommended setting and the one to use for logos, icons, UI screenshots, illustrations and almost every web image.
Maximum Shrink
The same idea pushed considerably harder for the smallest file. Flat graphics and simple icons hold up well. Smooth gradients and photographic areas may show faint banding, so check the result before you ship it — this is the mode to reach for when a size limit is non-negotiable.
A practical rule: flat colour and hard edges can be pushed as far as the tool will go; gradients and photographs should stay on Balanced; and if you cannot afford a single altered pixel, use lossless PNG compression. There is no cost to trying all three — the saved percentage is shown on the download button each time, so you can compare before committing.
4. How to Compress PNG Without Losing Transparency
This is the failure that sends most people looking for a different tool. You run a logo through an optimiser, open the result, and the transparent background has turned into a white box — or worse, a black one. It is the single most common complaint about image compression, and it usually happens because the file was quietly converted to a format with no alpha channel at all. Anyone trying to compress PNG without losing quality or transparency runs into it sooner or later.
That cannot happen here. A PNG goes in and a PNG comes out, and the alpha value of every pixel is carried through untouched in all three modes. Only the colour information is simplified. So when you compress a transparent PNG, the cut-out edges, the soft feathered shadow and the fully clear background all arrive exactly as they left — there is no white rectangle waiting for you when you drop the file onto a coloured page.
Two related things worth knowing. First, the pixel dimensions of your image are never changed by compressing it: a 2400 × 1200 PNG stays 2400 × 1200. If you also want it physically smaller, run it through the image resizer first, which is usually the bigger win of the two. Second, the compressed copy is a clean re-write of the picture, so incidental metadata from your camera or design app is not carried into the output — useful if you are publishing an image and would rather not publish where it came from.
5. “Compress PNG to 100KB”: Hitting a Specific Size
A lot of people arrive needing to compress PNG to 100KB, or to 200KB, or under whatever ceiling a job portal, a marketplace listing or a university upload form has set. Being straight about it: this tool has three modes and no target-size box. You cannot type a number and have a file appear at exactly that weight, and any tool promising that is guessing repeatedly behind the scenes until it lands close enough.
What works instead is a short, reliable sequence:
- Compress on Balanced first and read the new size on the download button. For most graphics this alone clears the limit.
- If it is still over, try Maximum Shrink on the same file and compare the two numbers.
- Still over? The problem is dimensions, not compression. A 4000-pixel-wide image cannot become a 100KB PNG while staying 4000 pixels wide. Cut the width down with the image resizer — or crop away what you do not need with the image cropper — then bring the smaller version back here and compress it.
Halving an image’s width removes three quarters of its pixels, which is a far larger lever than any compression setting. Resize first, compress second, and you will land under almost any limit without the picture looking mangled.
6. When PNG Is the Wrong Format for the Job
Sometimes the honest answer to “why is this file still enormous?” is that it should never have been a PNG. The format is superb for flat colour, sharp text, screenshots and anything with a transparent background, and a poor choice for a photograph, which has no flat areas to exploit and no transparency to protect.
If your image is a holiday photo, a portrait or a product shot with a solid background, the real fix is a different format rather than a harder compression setting. This tool deliberately keeps PNG in and PNG out; it does not quietly convert your file to something else behind your back, because a tool that silently changes a format is how transparency gets destroyed in the first place.
Two other limits worth stating plainly, since both are common searches when people set out to optimise images for a website. There is no bulk PNG compression here: the tool handles one image at a time, deliberately, so you always see the before and after size for the specific file in front of you. And there is no size cap or daily quota written into it — a very large image simply takes a little longer to work through than a small one. If what you are actually trying to slim down is a document rather than a picture, the PDF compressor is the right tool, and if you need the pictures out of a document first, use extract images from PDF and compress them here afterwards.
7. Why Cortexis Is the Best Free PNG Compressor
Plenty of sites will optimise a PNG for you. Most of them make it deliberately irritating until you pay. Here is what is different, stated plainly enough that you can check every line yourself.
Genuinely free, with no trial
No account, no email address, no credit card and no countdown to an upgrade prompt. The tool on this page is the entire product.
Transparency survives every mode
The alpha channel is carried through untouched whether you choose Lossless, Balanced or Maximum Shrink. No white box, no black box, no surprises.
No watermark on the output
Your image comes back clean. Nothing is stamped into a corner and nothing is added along an edge.
Your files stay private
Images are never stored on our servers, never retained after your visit, and never used to train or analyse anything.
You see the result before you commit
The original size, the new size and the percentage saved are all on screen, so you can switch modes and compare rather than guess.
Lossless really means lossless
Choose that mode and no pixel is altered — and if a rewrite would end up larger than your original, you keep the original size instead.
It sits alongside a wider set of free document and image tools built on the same terms, so once an image is compressed you can scale it up, pull a hex value out of it with the colour picker, or turn a link into a QR code without paying for any of it.
8. Frequently Asked Questions (FAQ)
How do I compress a PNG for free without losing quality?
Add your image to the compressor at the top of this page and choose the Lossless mode. Every pixel is preserved exactly, so the picture is identical to the one you started with. The savings are more modest than the other two modes, and if a rewrite would produce a larger file you simply keep your original size — you never end up worse off.
Will compressing a PNG remove the transparent background?
No. A PNG goes in and a PNG comes out, and the transparency of every pixel is carried through in all three modes. Only colour information is simplified, so cut-outs, soft shadows and fully clear backgrounds all survive intact.
Can I compress a PNG to an exact file size like 100KB?
Not directly — there is no target-size field, only three modes. In practice, compress on Balanced, check the size shown on the download button, and step up to Maximum Shrink if you are still over. If it will not come down far enough, the image is simply too many pixels wide: resize it first, then compress the smaller version.
Is there a file size limit or a daily limit?
There is no size cap and no daily quota. Compress one image or forty. A very large image takes a little longer to work through than a small one, which is the only practical difference.
Can I compress several PNG files at once?
Not in one pass — the tool takes one image at a time so that you always see the exact before and after size for that file. Use the Change PNG button to move straight on to the next one; there is nothing to reload and no counter running down.
Are my images safe when I compress them?
Your files are never stored on our servers, never retained after your session, and never used for training or analytics. Nothing you compress is kept, queued or logged.
Working on the same set of images? Use the image resizer to bring the dimensions down before compressing, the image cropper to cut away what you do not need, or the PDF to JPG converter to turn document pages into images in the first place. If you would rather understand image formats than simply use a tool, our free graphic design course covers colour, compression and export settings from the ground up.