Case Study: How an E-commerce Site Cut Bandwidth by 40% Using JPEG XL

This case study analyzes an e-commerce retailer that piloted JPEG XL for product photography and homepage hero images. Over a 12-week period they measured bandwidth, conversion impact, and operational costs to assess the migration.

Background and goals

The retailer had a catalog of 150,000 product images and faced high bandwidth costs and slow LCP on mobile. The goals were pragmatic:

• Reduce bandwidth for critical pages.
• Maintain or improve visual fidelity for product images.
• Keep rollout risk low with fallback strategies.

Pilot setup

The team selected 10,000 high-traffic product pages and implemented a phased pilot:

1. Encode new versions of images to JPEG XL (lossy) targeting perceptual parity with existing JPEGs.
2. Configure CDN for Accept header-based content negotiation; deliver JPEG XL to supported clients and JPEG for others.
3. Monitor bandwidth, load times, and conversion metrics.

Results

After 12 weeks the pilot showed measurable improvements:

• Bandwidth reduction: Overall bandwidth for pilot pages dropped by ~40% compared to baseline.
• Load times: LCP improved by an average of 220ms on mobile devices for pilot pages.
• Conversion: No statistically significant change in conversion rates was detected; product detail metrics remained stable.

Operational findings

The migration surfaced some operational considerations:

• Encoding costs: Encoding JPEG XL at scale required more CPU time, increasing batch processing costs modestly.
• Edge caching: CDN caches were effective; however, origin storage conversion was necessary for archival workflows.
• Fallback monitoring: They implemented analytics to ensure no clients were served corrupt or unsupported images after rollout.

"Adoption was a question of engineering trade-offs: slightly higher processing costs in return for sustained bandwidth savings and faster user experiences."

Recommendations from the team

• Start with a narrow pilot on high-traffic pages.
• Automate lossless recompression of legacy JPEGs into JPEG XL for archival savings.
• Monitor critical business KPIs continuously, not just technical metrics.

Conclusion

The pilot had a clear net benefit for the retailer: material bandwidth savings and faster page loads without hurting conversions. The team expanded JPEG XL delivery for the catalog incrementally and scheduled encoding infrastructure upgrades to reduce CPU costs over time. This case demonstrates a viable path for commerce sites to adopt modern image formats while mitigating risk.