Convert Images to JPEG XL

Encode images to JPEG XL (.jxl) format using cjxl. Supports lossless, visually lossless, and web quality presets, with optional effort (compression) tuning.

When to use

• Converting photos to JXL for archival, where file size matters and quality must be preserved.
• Lossless-transcoding existing JPEG files to save ~20% file size without re-compression artifacts.
• Creating web-optimized JXL variants with controlled visual loss.

Inputs to gather

• Input file or directory — single image, folder, or recursive tree. If omitted, ask for the path.
• Quality preset — ask which tier: lossless (full fidelity, -d 0), visually-lossless (imperceptible loss, -d 1.0, default), or web (visible compression acceptable, -d 3.0). Default: visually-lossless.
• Effort level — optional, range 1–9 (1 = fastest, 9 = slowest/best compression). Default: 7. Only ask if the user is concerned about speed vs file size.

Procedure

1. Check tooling