How to use it
- Press Choose files or Choose a folder, or drop your PNG images on the box.
- Leave Save as on JPG. Choose PNG instead when you're converting JPGs the other way.
- Pick the Background for transparent parts. White suits most documents and forms.
- Move the Quality slider to trade file size against sharpness. Changed it after the files were done? Press Apply to all again.
- Save each JPG with Download, or everything as a ZIP with Download all.
When JPG is the better format
JPG was made for photographs and other images with smooth changes of colour. Its lossy compression drops detail the eye barely notices, which is why a photo is usually far smaller as JPG than as PNG.
So convert to JPG when the PNG is mostly photo: a picture someone exported as PNG, a screenshot of a photo or a video frame, or a scanned print. The file becomes much easier to email, attach or upload, and the difference is hard to see.
When to keep the PNG
PNG is lossless. Mozilla's format guide recommends lossless formats for screenshots, diagrams, logos and line art, because the blur and coloured fringes that lossy compression causes around text and sharp edges are very visible. Keep the PNG for:
- Screenshots of text, code, spreadsheets or app windows
- Logos, icons and diagrams with flat colours and crisp edges
- Images that need a transparent background
- A master copy you'll edit again later
If a PNG of a screenshot is simply too big, the image compressor can shrink it while keeping it a PNG.
Transparent parts and the background colour
JPG can't store transparency, so transparent pixels must become a solid colour. The tool blends them onto the colour in Background for transparent parts. Half-transparent pixels, such as the smoothed edge of a round logo, are mixed with that colour, which keeps the edge soft.
Choose the colour of wherever the image will appear. A logo meant for a dark slide, converted onto white, gets a thin pale halo around its edges; converted onto the slide's own colour, it fits in. If a PNG has no transparent pixels, the colour makes no difference.
What the Quality number means
Quality runs from 10 to 100 and controls how much detail the JPG encoder (MozJPEG) keeps. Higher numbers keep more and make bigger files; lower numbers save space and, at some point, show blocky patches and smudged edges. The hint under the slider calls 80 a good balance. This page starts at 90, because PNGs often contain text, where losses show first.
If a form sets a maximum size, type it into Make every file smaller than under More options instead of guessing. The tool tries lower quality steps until each file fits, and only then reduces the pixel size. A limit of 200 KB here means 200,000 bytes.
JPG to PNG: what it can and can't do
Saving a JPG as PNG is useful when a program insists on PNG, or when you will edit the image several times: each time a JPG is edited and saved again, it is compressed again, while a PNG copy is stored as it is.
What it can't do is restore quality. The detail JPG compression removed is gone, so the PNG is an exact copy of the JPG's pixels, blocky patches included, in a bigger file.
Questions
- Will my image lose quality as JPG?
- A little, because JPG is lossy. For photos the change is hard to spot at the default quality; for sharp text and thin lines it shows sooner, which is when PNG is the better choice.
- Why did the transparent background turn white?
- JPG has no transparency, so the see-through parts are filled with the colour in Background for transparent parts, white by default. Pick a different colour and press Apply to all again.
- Do the JPGs keep any hidden photo details?
- No. JPGs made on this page are saved without photo details (EXIF). To keep the date taken from a camera photo, use the image converter, which has that option.
- Can I convert a whole folder of screenshots?
- Yes. On a computer, press Choose a folder; every image in it is converted with the same settings. There's no limit on the number of files.
- Is my file uploaded?
- No. The conversion runs in your browser on your own device, and the JPG is saved straight from there. Nothing reaches a server.