Compress PNG

Compress bulky PNG files to a more manageable size without uploading files to an unknown server. Open or drop one PNG file or up to a thousand per batch, select a preset or enter a target size, compress, then download. Transparency will be preserved (for transparent PNGs).

What is a PNG file?

A PNG file (Portable Network Graphics) is an image format created as a free alternative to GIF after Unisys announced it would charge royalties for software that read or processed LZW (a compression algorithm GIF files used). Basically, every browser, graphics software, or website would owe money to Unisys if it used a GIF file.

PNG files are lossless, meaning every pixel is stored as is. There’s no quality loss even after saving them again and again, unlike JPG files, which get blurrier with each re-save because a small portion of the pixels get distorted. Another advantage of PNG over lossy formats like JPG is that it supports transparent backgrounds. This is great for logos, icons, screenshots, and anything that needs crisp, clear graphic lines or text with no distortion.

Unfortunately, PNG’s lossless nature means larger file sizes. For example, a screenshot that’s around 180 KB could balloon to over 1.5 MB if saved as a PNG file. A whole folder of UI screenshots for a knowledge base for a software company would mean hundreds of megabytes, if not gigabytes, of storage wasted, which adds up to higher hosting costs, in addition to slow-loading websites that get penalized by Google.

This tool aims to address that.

How to compress PNG files?

1. Open or drop PNG files: You can open a single PNG file or batches of up to 1,000 files. For larger PNG files, lower that number to 100–200.
2. Choose a preset: The balanced option is a good starting point for most PNG files. If you need more compression, choose Strong. If you have a target size in mind, switch to “Target size” and enter your target number.
3. Preview result: You can see a preview of how the image would look before it’s compressed. If you’re happy with the results, proceed and compress the files.
4. Download: You can download the files individually or everything at once as a ZIP file.

Nothing is uploaded to a server, so you can compress project files or confidential screenshots without worrying about anyone stealing your ideas.

What to expect

• Typically, PNG files will compress between 60 and 80% using the Balanced preset. The biggest beneficiaries would be screenshots or UI images at the higher end of that range. Unfortunately, photographs or images with more complex graphics compress less.
• Images with fewer colors will compress by 85% or more without visual degradation.
• PNG files with a transparent background will be preserved by default, as well as the dimensions, unless specified. So a 2,000 × 2,000 pixel PNG file will retain the same dimensions but at a smaller file size.
• This tool will work even on PNG files a few hundred megabytes, but that would depend on how much memory your system has. If your computer has less memory, the browser may stall, which can also happen with graphics software like Adobe.
• After compressing, you’ll see the total number of KB saved, average percentage, and the number of files processed.

Options Tab (for people who like to tweak)

Here’s what each option under the “Options” tab do.

1. Palette reduction: This feature converts a PNG file to 256 colors, so a PNG that may have 600 colors becomes 256, which is great for logos, screenshots, or UI illustrations.
2. Palette size (16–256 colors): Note that this feature will only appear when you turn on the “Palette reduction.” PNG files can store up to 256 distinct colors. Fewer colors translate to a smaller file size, but smooth gradients won’t be as smooth and will turn into stripes. For the best quality, leave it at 256 for logos or more complex illustrations.
3. Preserve transparency: It is self-explanatory. Leave it on to retain the transparent background. If you want more compression and a flat background, turn it off.
4. Strip metadata: This feature removes EXIF data, color profiles, and other text data stored (like the software used to create the graphic). This saves additional space, and I suggest turning it on if you’re sharing the PNG file on a website.
5. Max width (px): Enter a custom width to resize the whole batch of PNG files if you want to reduce them to a specific size for social media or uploading to a website.

How does PNG compression actually work?

PNG compression has two layers, and this tool uses both.

The first layer is called “Palette quantization (lossy).” Typically, a PNG file stores millions of possible colors per pixel, and most images don’t need to use all of them. Quantization reviews the image, selects the 256 (or fewer) colors that best represent it, then rewrites every pixel to use each one of those colors. If done properly, you won’t notice the difference. This is where most file savings come from, usually chopping 60 to 80% off the original file size.

The second layer is called Zlib re-encoding (lossless). After the first layer (or the quantization process), the file is still valid PNG data, but it’s still not as compact as it could be. A second pass inspects the file and tries dozens of compression strategies, and chooses the smallest result.There’s no pixel change, and this typically shaves another 5–15% of unnecessary bloat.

This tool uses WebAssembly builds of “pngquant” (layer 1) and “oxipng” (layer 2), which is the same stack that tools like ImageOptim, TinyPNG, and Squoosh.app use.The only difference is that ConvertYard runs it in your browser and not on another server.

Why “in your browser” matters

Most free PNG compressors I tested upload your file to a server, compress it there, then provide a link to download it. So this means:

1. Your PNG files are uploaded to a stranger’s computer (at least temporarily).
2. You’ll need to wait for the files to upload first before compression (which takes longer if you’re compressing larger files).
3. Since these websites rely on a server to process images, they have a size cap (usually 5 to 10 MB per file).
4. Your files are exposed if there is a data breach or leak.

ConvertYard runs the whole system inside the browser. Files aren’t uploaded to a server. It processes larger files faster because you don’t have to wait for the upload to finish, which is great if you have a slower connection. And there’s no limit on how many PNG files you can compress as long as your computer’s memory can handle it. For larger PNG files, I would recommend limiting it to 100 to 200 per batch, lower for high-resolution files.