The WebP format, launched by Google in 2010 and standardized across every major browser since 2020, is today the default image format recommended for e-commerce. It compresses better than JPEG, supports transparency like PNG, and is readable everywhere. For a Shopify or PrestaShop merchant with 2,000 to 20,000 SKUs, switching to WebP often means several seconds shaved off LCP and a direct lift on Core Web Vitals.
This guide covers everything you need to know: the technical side, browser support, conversion rules, pitfalls to avoid — and, at the end, how Seegea automatically converts your entire product catalog to WebP without Photoshop, without a Node.js script, without risking a broken listing.
WebP vs JPEG vs PNG vs AVIF: the technical comparison
Before comparing, each format was built for a specific use — none is objectively "better" in absolute terms.
- JPEG — created in 1992, lossy compression, no transparency. The most universal format but aging. Typical size for a 1000×1000 product packshot: 180 to 250 KB.
- PNG — created in 1996, lossless compression, supports transparency. Great for logos and flat illustrations, terrible for photos. Typical packshot size: 900 KB to 1.5 MB.
- WebP — created by Google in 2010, supports lossy and lossless, transparency, animation. Typical packshot size: 45 to 90 KB.
- AVIF — created in 2019, compresses even better than WebP, slower to encode. Typical size: 30 to 70 KB. Safari support is decent but incomplete on Safari 15.
The concrete impact on Core Web Vitals
Google Search Console has used three performance metrics as ranking signals since 2021: LCP, CLS and INP (which replaced FID in March 2024). Images weigh heavily on LCP (Largest Contentful Paint) because, on most product pages, the main image is the LCP element.
Real measurement on a Shopify catalog of 4,800 products moved to WebP:
- Main image average weight: 246 KB → 78 KB (−68%)
- Mobile median LCP: 3.9s → 2.1s (−46%)
- Lighthouse Performance score: 48 → 82
- Bounce rate on product pages: 54% → 47%
These are not theoretical numbers: the gap between a 4s LCP and a 2s LCP is often the factor that moves your page from "needs improvement" to "good" in Google Search Console, with direct impact on organic impressions.
Conversion rules you need to follow
Quality level: between 75 and 85
Most WebP encoders (cwebp, Sharp, Squoosh) use a quality setting from 0 to 100. Below 70, artifacts appear clearly on gradients. Above 90, you gain little compression for a lot of weight. The e-commerce sweet spot sits between 75 and 85, with 82 as the recommended default.
Lossy or lossless?
For product photos, always WebP lossy. Weight savings are massive (60 to 75%) and the quality loss imperceptible. For logos, illustrations, icons, UI screenshots, WebP lossless. Savings are smaller (20 to 30%) but sharpness is preserved.
Pixel dimensions
A 4000×4000 WebP is still heavy, even well compressed. Before conversion, resize:
- Shopify master image: 2048×2048 (retina ready)
- Google Shopping image: 1000×1000 minimum, 1600×1600 recommended
- Grid thumbnails: 600×600
- Mini thumbnails: 300×300
Always keep the original
That's the golden rule. Never delete the source JPEG or PNG until you have validated the WebP output in your theme, on mobile and desktop, across several listings. If your WebP is too compressed or breaks a detail, you need to be able to roll back.
Browser support: where are we in 2026?
Since Safari 14 (September 2020), every major browser supports WebP natively. Can I Use numbers as of January 1st, 2026:
- Chrome, Edge, Opera, Samsung Internet: since 2014
- Firefox: since 2019
- Desktop Safari: since Safari 14 (Big Sur, September 2020)
- iOS Safari: since iOS 14 (September 2020)
In 2026, 97.3% of e-commerce users worldwide see WebP without any fallback. The remaining 2.7% are very old browsers (IE11, Safari 13) or bots and scrapers. For those cases, the HTML <picture> tag serves a JPEG automatically.
Seegea plugs into your e-commerce stack
The 3 most common pitfalls (and how to avoid them)
Pitfall 1: converting without regenerating Shopify sizes
Pitfall 2: alt text lost during migration
Pitfall 3: too aggressive compression on jewelry/textiles
How to convert a catalog to WebP: 4 approaches
Option 1: Photoshop (50 products max)
File → Export As → WebP. Works since Photoshop 23.2 (2022). Viable for a < 50 SKU store, impossible beyond.
Option 2: online tools (200 products max)
Squoosh.app (Google), TinyPNG, CloudConvert. One upload at a time, no batch, no CMS integration. Fully manual.
Option 3: Node.js script with Sharp (technical)
If you have a developer, Sharp does the job with sharp(input).webp({quality: 82}).toFile(output). Still to handle: pulling images from Shopify via GraphQL API, pushing new versions, error handling, deleting old ones. Budget 1-2 engineer-days for a robust script, plus ongoing maintenance.
Option 4: Seegea (any catalog)
Multi-select in the grid → "Convert to WebP" button → choose quality → validate. Seegea pulls high-resolution images from Shopify or PrestaShop, converts them with Sharp server-side, re-pushes them via API preserving alt text, and creates a product version for each change — so Ctrl+Z restores everything if a visual was badly compressed.
What Seegea does on your images, exactly
Bulk WebP conversion
Smart resizing
AI alt text
| Criterion | Without Seegea | With Seegea |
|---|---|---|
| Converting 2,000 images to WebP | 2-3 days in Photoshop | 8-12 minutes, batched |
| Alt text preservation | Manual check | Automatic |
| Re-push Shopify/PrestaShop | Manual re-upload | Via API, transparent |
| Rollback if visual fails | Impossible without backup | Ctrl+Z per product |
| AI alt text | Separate third-party tool | Built-in, 1 click |
| Total cost (5000 products) | Intern 2 weeks ~$2,700 | $20 to $65/month |
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Advanced technical questions
Animated WebP: can it replace GIFs?
Yes. Animated WebP (since 2013) compresses 3 to 5 times better than a GIF at equivalent quality. For animated product demos on listings, it's the default format. Watch out: on Shopify, only GIF is accepted in the native "image" field; for animated WebP, you need a metafield or a custom section.
Lazy loading and WebP
WebP doesn't interfere with native lazy loading (loading="lazy") at all. The two combine perfectly and the Core Web Vitals effect is multiplicative: lighter image + loaded only when visible = LCP plummets.
CDN and WebP
Shopify CDN and most modern CDNs (Cloudflare, Bunny, CDN77) automatically serve the best version (WebP or AVIF) based on browser Accept headers. You upload a WebP, the CDN may serve AVIF to a compatible visitor. No action needed on your side.
Conclusion: where to start?
If your catalog has more than 500 products and most images are still JPEG or PNG, switching to WebP is the performance lever with the best effort-to-gain ratio you can activate in 2026. Before redesigning your theme, before buying a cache plugin, before migrating your CDN: convert your images.
Seegea was built in France, between Annecy and Chantilly, for Shopify and PrestaShop merchants who want to stop losing nights fixing and optimizing their catalog. WebP conversion, resizing, AI alt text, AI description, full rollback: all in one tabular interface, pushed to your CMS in real time.