How to batch convert images between JPG and PNG
By the Converterzilla Team
We build privacy-first PDF and image tools that run entirely in your browser. Our team has shipped JavaScript file-processing apps used by thousands every day, and we write here about the libraries, trade-offs and patterns we use.
Converting a single image between formats is trivial — most operating systems have it built in. The pain shows up when you need to convert a folder. Doing it one-at-a-time gets tedious fast, and macOS/Windows built-in tools usually don't support batch.
What "batch" actually means
True batch conversion means: drop many files at once, set the target format once, and get back many converted files in one operation. No clicking through prompts. No five-second wait between each.
Browser-based vs desktop
Desktop tools are fine if you have one set up. Most people don't, and downloading a 30 MB installer for a five-minute task is a poor trade. Browser-based batch converters work without installation and process files locally — same speed as desktop tools, none of the setup.
Quality settings to know
- JPG quality 92% — visually lossless for photos, ~50% smaller files than 100%
- JPG quality 80% — good for web, ~70% smaller than 100%, slight visible compression on close inspection
- PNG quality — N/A, PNG is lossless, "quality" only changes encoding speed
Drop a folder of mixed JPGs and PNGs into our batch converter and pick the target format. Each file converts and downloads in sequence — typically under a second per image.