How to compress images in your browser without uploading them

I’m the creator of FoxPNG, a free image compressor and converter. Here’s how to use it without sending your images to a server for processing.

1. Test one image first

Open https://foxpng.com/ and add an image. Compression starts when you add it. Keep the original until you’ve checked the result.

2. Choose a format

To add another format for a static image, turn on Convert images and select the outputs you need.

For photos, try JPEG or WebP. Avoid JPEG if you need transparency. PNG is a good starting point for screenshots, logos, and graphics with text. You can also try WebP if the site or app where you’ll use the image supports it.

For a PNG you want to compress without changing its pixels, open Advanced settings and set PNG mode to Lossless. An already optimized PNG may barely shrink.

3. Check the result

For a lossy output, start with the default Image quality setting under Advanced settings. After changing settings, click Recompress with current settings.

Download the result and view it at the size you’ll use. Check small text, sharp edges, and gradients. If you notice blur or banding, try a higher quality setting.

Compare file sizes, too. Converting to another format can make a file larger. Keep the original if the result doesn’t help.

4. Run the batch

Once you’re happy with the settings, add the remaining images. When processing finishes, click Download ZIP. If you’re working with both photos and screenshots, test one of each first. They may need different settings.

FoxPNG processes images locally in your browser. Your files aren’t uploaded for compression or conversion, though loading the page and analytics can still make network requests.

Supported formats and limits are listed in the guide: https://foxpng.com/guide.html

If an image gives you trouble, tell me its format and what went wrong. Please don’t post private images here.