How to Compress PNG Images Online to a Target File Size

Before you start

A PNG compressor can reduce file size through lossless compression or by removing unnecessary image data. If you need a specific limit such as 2MB, 500KB or 100KB, start with the highest-quality source file you have. Repeated compression of an already compressed PNG can increase artifacts in tools that use lossy processing, so keep a copy of the original before changing anything.

Most online PNG compressors work in the browser and do not require an installed program. Check whether the tool uploads the file to a server or processes it locally before you choose it, especially if the image contains private information. For a predictable result, note the current file size and pixel dimensions first; those details help you judge how much reduction is realistic without changing the image too much.

Keep the aspect ratio unchanged unless you intentionally need to crop or resize. Resizing changes pixel dimensions and usually affects sharpness, while compression aims to reduce storage size within the same visible frame.

Step-by-step instructions

The exact labels vary between free online PNG compressors, but the main workflow is similar.

1) Open the online PNG compressor and add the image you want to reduce.

2) Wait for the tool to read the file and display the starting size.

3) Select a compression level if available. Start with the default or medium setting rather than the strongest option.

4) If the tool has a target size option, enter the required value. Otherwise, compare the previewed result with your target after the first pass.

5) Download the compressed PNG and check that it still opens correctly.

6) If the result is still above the required limit, try a higher compression setting or reduce the pixel dimensions. If the result is too small or visibly damaged, return to the original and use a weaker setting.

Some tools offer a specific mode for changing file size rather than quality. In that mode, the converter adjusts the output to fit the requested number as closely as the source allows. A very large PNG cannot always reach 10KB without substantial quality loss, so treat the target as a guide rather than a guaranteed result.

Check the output

After downloading, view the compressed PNG at 100% zoom and compare it with the original. Look for banding in gradients, rough edges around text, color shifts or visible noise in flat areas. These are signs that the compression setting was too aggressive.

Open the file properties or details panel to confirm the final size in kilobytes or megabytes. If the image must stay below a limit such as 100KB, 200KB or 2MB, verify the actual size on your device, because a preview may round the number differently.

For images with transparency, check the transparent areas against both light and dark backgrounds. Some online compressors preserve the alpha channel, while others may fill transparent regions or convert the image to a different file format automatically. If transparent pixels appear white, black or gray, the output is not suitable for use as a transparent PNG.

Common problems and next steps

A common issue is that the compressed file is only slightly smaller than the original. This often happens when the source is a photo saved as PNG. Photos contain many unique pixel values, so lossless PNG compression cannot reduce them as much as screenshots, logos or images with large flat regions. For a photo, converting to a suitable format may produce a smaller file, but that changes the file format and may remove transparency; do this only when PNG is not required.

If you cannot reach 500KB, 256KB or 100KB without visible damage, reduce the pixel dimensions in small steps while keeping the aspect ratio locked. Reducing a 4000-pixel-wide image to 2500 pixels often helps more than increasing compression alone. Do not repeatedly upscale a small source to appear sharper; upscaling cannot restore detail that was not recorded.

A few online tools limit the largest input file or the number of images you can process without payment. If a free PNG compressor refuses a large file, check the stated file-size or dimension limit. You can then try another tool, split the work into smaller batches, or reduce the source dimensions in an image editor before compression.

When the downloaded file does not open or appears corrupted, download it again instead of editing the broken copy. Avoid renaming the file to another extension unless you are deliberately converting the format; changing only the extension does not change how the image data is stored and can make the file harder to open.

For consistent results, process each version from the untouched original rather than compressing the same output again. Record the setting that reached your target so you can reuse it for similar screenshots, web graphics or scans.