Converting images to WebP using coding agents

By Pradyumna Chippigiri

January 18, 2026

When i am ship my blog pages, i try and convert my pngs/jpegs to WebP as it can cut transfer size drastically. I now let coding agents batch-convert PNG/JPG assets and update references automatically. I just give a prompt like this to cursor/codex: (you can change it accordingly)(just for context)

Convert all PNG images used in page.mdx to WebP. Save them under 
public/images/ 
update the MDX references to .webp, and remove the old PNGs after verifying the new images load

Internally it runs this command :

for f in public/images/**/*.png; do cwebp -q 80 "$f" -o "${f%.png}.webp"; done

Meaning (piece by piece):

• for f in public/images/**/*.png; do ... done loops through all PNG files under public/images/ including subfolders. **/ is a recursive glob (works in zsh, or in bash)
• cwebp -q 80 "$f" -o "${f%.png}.webp" converts each PNG to WebP:
  • -q 80 sets quality to 80 (good balance of size vs quality)
  • "$f" is the input file
  • -o ... is the output path
  • ${f%.png}.webp keeps the same filename and swaps .png → .webp
  • This does not delete the original PNG; it creates a new .webp next to it.

cwebp does the real work. It re-encodes PNG data into WebP, which is what usually reduces file size.

If you use lossy WebP (-q 80 like above), you may see a tiny quality drop. If you want no quality loss, then u can tell that to the agent it will do it for you, but internally it does something like this:

cwebp -lossless input.png -o output.webp

Lossless keeps quality intact, but file sizes may be larger than lossy.

Why it helps

• Smaller payloads → faster LCP (you can test in PageSpeed Inisghts) and better mobile performance.
• Keeps quality high with ~70–85 WebP quality.