How to Convert Multiple PNGs to JPG at Once

Drop a folder of PNGs into a batch converter at quality 80–90 and watch gigabytes become megabytes — with the transparency and quality traps to avoid.

Short answer: drop the whole folder into a batch converter, set JPG quality to 80–90, and download the results as a ZIP. A screenshot folder measured in gigabytes comes back as megabytes — for photos and screenshots, JPG runs 60–90% smaller than PNG with no visible difference.

Why the files shrink so much

PNG is lossless: it stores every pixel exactly, which is perfect for sharp graphics but wasteful for photos. JPG is lossy: it throws away visual detail your eyes barely register. On screenshots and photographs the two look identical at quality 85 — but the JPG is a fraction of the size.

The transparency trade

JPG has no alpha channel, so anything transparent gets filled with a solid color — usually white. That's fine for screenshots and photos, which have no transparency anyway. But logos and icons with transparent backgrounds come back with a white box around them. If transparency matters, keep the PNG.

The quality sweet spot

90 and up: screenshots with small text. Keeps letter edges crisp.
80–85: photos. Visually identical to the original, much smaller files.
Below 70: only when a file has to squeeze under an upload limit. Expect visible artifacts.
100: pointless. Enormous files, no visible gain over 90.

Keep it local

Screenshots often contain personal information — chats, account numbers, open tabs. A converter that runs entirely in your browser never uploads them anywhere. You can prove it: load the page, switch to airplane mode, and convert. If it still works, your files never left your device.

The traps

White boxes on logos: converting a transparent PNG fills the alpha with white. Check the results before you ship them.
Re-compressing JPGs: every JPG save throws away more detail. Always convert from the original PNG — never JPG to JPG to JPG.
Tiny PNGs barely shrink: flat-color graphics and icons are already small. Batch conversion pays off on photos and screenshots, not 2 KB icons.
Forgetting the originals: conversion is one-way for the discarded detail. Keep the PNGs until you're sure the JPGs are good.

# ImageMagick: convert every PNG in the folder at quality 85
mogrify -format jpg -quality 85 *.png
# Originals are kept — new .jpg files appear alongside them

Try it

Drop a whole folder into the Batch Image Converter — set the quality, convert everything at once, and download the results as a ZIP, all in your browser with nothing uploaded.