I Benchmarked 17 Image Conversions on My Production Server. Some Results Were Not What I Expected.

I run Convertify, a free image converter built on Rust and libvips. Last week I decided to stop guessing about format performance and actually measure it. I took 50 real images (26 PNGs, 24 iPhone HEIC photos), ran 17 conversions through the production pipeline, and recorded every file size and encode time.

Some results confirmed what everyone says. Others did not.

The three results that surprised me

1. Converting HEIC to JPG makes files 14% bigger, not smaller.

This one hurt. "Convert iPhone photos to JPG" is probably the most common advice on the internet. But HEIC wraps the HEVC codec, which compresses roughly 2x better than JPEG. Going from a better codec to a worse one means the file grows. Every time.