How to Optimize JPG and PNG Images Together Online

Before you start

Check whether the tool runs locally in your browser or uploads files to a remote service. Browser-based compression keeps files on your device, while server-side tools send them over the internet. For JPG, decide whether you need a smaller file or maximum visual quality; for PNG, confirm whether the image uses transparency, because that limits which output formats you can choose.

Step-by-step instructions

Open the online optimizer and add your JPG and PNG files. If the tool supports batch mode, select both formats at once; otherwise process them in separate groups but use the same output settings so the results stay consistent.

Choose a compression mode. For JPG, set the quality level or select a preset such as balanced or aggressive. Lower quality values produce smaller files but can introduce visible artifacts. For PNG, use lossless compression when pixel-exact output matters, or choose lossy optimization when a smaller file is more important than preserving every color.

Keep pixel dimensions unchanged unless the image will be displayed at a smaller size. Resizing is separate from compression: it reduces the width and height, while compression reduces file size by changing how the image data is stored. If the tool includes resizing, adjust it only when the current dimensions are larger than needed.

Preserve the aspect ratio when changing dimensions. Most tools keep width and height linked by default. Enter one value and let the other update automatically, or confirm that the proportions remain the same.

For PNGs with transparency, do not convert them to JPG unless you are prepared to lose the transparent areas. JPG does not support transparency, so those regions may be replaced with a solid color such as white or black. Keep transparent images as PNG or use a format that supports alpha channels.

Run the compression and download the optimized files. If the tool offers ZIP output for batches, download the archive and extract it. Otherwise save each file individually and compare its size with the original.

Check the output

Compare the file size before and after compression. The output should be smaller than the source, but the amount will vary by image content and settings. Open the optimized image at normal viewing size and look for obvious banding, blur, color shifts, or blocky areas, especially around text and sharp edges.

For PNG, verify that transparency remains intact if the original contained it. Check the file format after processing: a JPG should still be a JPG and a PNG should still be a PNG unless you deliberately converted it.

Common problems and next steps

If a JPG looks worse after optimization, increase the quality setting and compress again. Starting from the original file gives the best result, because each repeated JPG save can add further artifacts.

If a PNG becomes larger after optimization, check whether the source already used efficient compression. Some tools may add metadata or change the internal compression method. Try a lossless mode without metadata removal, or compare the output from a different optimizer.

If transparent PNG areas turn solid, the file was likely converted to JPG or flattened. Use a PNG output option and confirm that the original file actually contains transparency rather than a white background baked into the image.

For smart JPG and PNG compression, keep the purpose of each image in mind. A product photo can tolerate more aggressive optimization than a screenshot with small text. When the tool supports it, process similar image types with matching settings so a set of exported files has a consistent look.