PNG, JPG or WebP? — I Converted the Same 3 Images and Measured the File Sizes

You try to upload a photo and get "file too large." Or you save a transparent logo and the background turns solid black. Both come down to picking the wrong image format.

"WebP is the smallest" and "use JPG for photos" are common advice — but measuring is the surest way to know. So I converted three very different images to PNG, JPG and WebP and compared the sizes.

1. Results — same image, different format

I used the same method as this site's Image Converter (Chrome's canvas encoder). Dimensions stay the same; only the format and quality change.

⚠️ marks results where the transparent background turned black. Small, but not usable.

2. The three formats work differently

• PNG keeps every pixel, so complex photos balloon in size
• JPG throws away detail you are unlikely to notice, and cannot store transparency
• WebP, made by Google for the web, compresses lossily and keeps transparency

3. Three things the table shows

① A photo saved as PNG is 11 times larger. The same photo was 3,566KB as PNG and 321KB as JPG — with no visible gain.

② WebP dominates for screenshots. One thirteenth of the PNG (433KB → 32KB) and less than half the JPG. Large flat areas of color compress especially well in WebP.

③ At high quality, WebP can be larger. At quality 80 the WebP photo was 18% smaller, but at quality 95 it flipped: WebP 552KB vs JPG 463KB. Google reports WebP is 25–34% smaller than JPEG at equal visual quality — the quality numbers themselves don't mean the same thing across formats, so comparing equal numbers can reverse the result.

💡 Start with a quality between 70 and 85. On most screens it is hard to tell apart from the original, and the file shrinks a lot.

4. Three traps when converting

Transparent areas turn black in JPG

JPG has no concept of transparency, so transparent pixels are filled with black (RGB 0, 0, 0) — exactly what happened to the icon above. Save logos, icons and stickers as PNG or WebP. The WebP icon kept its transparency at one fifth of the PNG size.

Location and camera data disappear

Phone photos carry GPS location, camera model and capture time (EXIF). Converting in the browser redraws the pixels into a new file, so all of that is dropped — I checked with a photo containing GPS and camera tags.

• 👍 Useful for stripping your home location before sharing a photo
• 👎 If you sort photos by capture date, that date is gone from the converted copy — keep the original

Re-saving JPG over and over degrades it

JPG discards a little information every time it is saved. Edit first, convert once at the end, and keep the original in its first format.

5. What to pick

All modern browsers display WebP. Some older apps or upload forms may not accept it — switch to JPG only then.

Wrap-up

• Don't save photos as PNG (11x)
• For the web, WebP at about 80 is usually best
• Never JPG for transparent images
• Converted files don't keep location data

In the Image Converter you see the before/after size immediately, so finding the right setting for your image takes seconds. Images never leave your browser.

Test setup: October 2026, Chrome canvas encoder (toBlob). Results vary with the browser and the image content.