What happens to a transparent background when I convert PNG to JPG?

It is filled with white. To keep a transparent background, save as PNG or WEBP.

How do I make an image file smaller?

Pick JPG or WEBP and lower the quality, or reduce the width and height. After saving, you can see the original and the result sizes side by side.

No. The converted image is saved as a new file, and the original stays as it is.

Convert image format

Convert to PNG, JPG, WEBP or BMP, and resize if you like. Your files stay on your device.

PNG·JPG·WEBP·GIF

Converts one image to PNG, JPG, WEBP or BMP, whichever you choose. You can also change its width and height.

Drop an image file onto the screen, or click to choose one.
Under “Format”, pick the “Save as” format: PNG, JPG, WEBP or BMP. It starts on WEBP.
If you picked JPG or WEBP, set the quality with the “Quality” slider. It starts at 90%.
To change the size, write the width or height in pixels under “Resize”. Leave them empty to keep the original size.
Click “Convert”, then “Save”. The file name is the original name with “-converted” added, and the extension is the format you picked.

PNG is sharp and keeps transparent backgrounds, with larger files. JPG suits photos and makes small files. WEBP is good for the web and makes small files. BMP is uncompressed, so its files are very large.
With JPG and BMP, transparent backgrounds turn white. The quality slider only appears for JPG and WEBP.
With “Keep aspect ratio” on, writing just the width or the height sets the other to match the proportions. Turn it off to set width and height separately. Keep both at 8192 pixels or less.
If this browser cannot create a format, you are told it could not be saved. Then choose PNG or JPG. Files are processed in your browser and are not uploaded to a server.

What happens to a transparent background when I convert PNG to JPG?: It is filled with white. To keep a transparent background, save as PNG or WEBP.
How do I make an image file smaller?: Pick JPG or WEBP and lower the quality, or reduce the width and height. After saving, you can see the original and the result sizes side by side.
Does it change my original image?: No. The converted image is saved as a new file, and the original stays as it is.