BigCommerce image specs and what to upload
BigCommerce accepts product images up to 8 MB each, and the platform generates responsive variants automatically through its image manager. Upload size matters less than aspect ratio consistency — but uploading at too low a resolution caps how sharp the largest displayed variant can look.
| Slot | Recommended upload size | Aspect ratio |
|---|---|---|
| Product gallery (primary) | 2048 × 2048 | 1:1 |
| Product gallery (lifestyle) | 2048 × 2560 | 4:5 |
| Category thumbnail | 1280 × 1280 | 1:1 |
| Homepage carousel | 2560 × 1440 | 16:9 |
| Brand logo | 500 × 500 (PNG) | 1:1 |
Stencil themes use the getImage Handlebars helper with named size keys (zoom, hero, productview, thumbnail). The platform serves a downsized variant matching the requested key, so uploading at 2× the largest key your theme uses is the safe default.
Formats, WebP, and the Akamai CDN behavior
BigCommerce serves images through Akamai with automatic WebP conversion for browsers that send the image/webp Accept header. The original format you upload is still stored at the source, but visitors almost always receive the optimized WebP variant.
Upload JPEG at quality 85 for product photography. Reserve PNG for graphics that need transparency — logos, badges, ghost mannequin cutouts. PNG uploads of photographic content waste storage and don't yield smaller WebP outputs.
AVIF is not part of the automatic conversion pipeline as of 2026 on stock Stencil themes. If you're running headless commerce against the BigCommerce API, you can opt into AVIF through your own delivery layer.
Alt text, filenames, and product image SEO
Each product image in BigCommerce has a Description field — this becomes the alt attribute on the rendered <img> tag. The field is empty by default, and most BigCommerce stores never fill it in. That's free SEO real estate.
Weak alt text
- "product-main.jpg"
- "image1"
- "DSC_0143"
- "buy black running shoes online"
Strong alt text
- "Black running shoe with white sole, side profile"
- "Black running shoe on white background"
- "Black running shoe worn outdoors on trail"
- "Heel cushion detail of black running shoe"
Filenames matter too. BigCommerce keeps the upload filename inside the CDN URL path, and Google uses URL tokens as a weak ranking signal. Rename your files before uploading — there's no rename action in the product image manager.
For structured data, BigCommerce's default product schema includes the image property automatically. The job on your end is making sure those images load fast and stay at stable URLs.
Stencil themes, Core Web Vitals, and the LCP fix
Stencil themes lazy-load below-the-fold images by default. The trap is the same one Shopify stores hit: the LCP element — usually the first product gallery image — sometimes gets loading="lazy" applied too, which delays paint and hurts mobile scores.
Check your theme's templates/components/products/gallery.html (or your theme's equivalent). The first image should render with loading="eager" and fetchpriority="high". If both attributes are absent or set to lazy, that single change can drop LCP by 300–600 ms on mobile.
The other Core Web Vitals pitfall: third-party apps that inject unsized images into product pages cause cumulative layout shift (CLS). Run a Lighthouse audit and look for "image elements do not have explicit width and height" — the offenders are almost always recently-installed apps, not core Stencil.
Catalog consistency: the bigger conversion lever
Technical optimization caps out fast. The compounding gain on BigCommerce stores comes from visual consistency across the catalog: same aspect ratio, same background, same shadow direction, same framing.
When a shopper scrolls a category page and the products look like they came from twelve different photographers — because they often did — the brand reads as low-trust. The fix is a written spec everyone shooting or editing your catalog follows:
- One canonical aspect ratio for the primary image (1:1 is the safest default for BigCommerce category grids)
- One background color, specified as a hex value, not "white"
- One shadow direction and intensity (or commit to no shadow)
- One framing rule — e.g., product fills 80% of frame, centered
For catalogs already built with inconsistent images, an AI product photo tool like Retouchable can normalize backgrounds, regenerate shadows, and unify framing across hundreds of SKUs without reshooting — at a fraction of traditional retouching costs.
A 15-minute BigCommerce image audit
Run this on your highest-traffic product page and your highest-traffic category page:
- PageSpeed Insights — check mobile LCP and image-specific opportunities
- View Source — confirm your first product image has
loading="eager"andfetchpriority="high" - Inspect the <img> tag — confirm
srcsetis present and width/height attributes exist - Check the CDN URL — Akamai should serve
.webpin Chrome's network panel - Review every gallery image's Description field — descriptive alt text on each
- Scroll your top category page — same aspect ratio, background, and framing across products?
- Lighthouse "Best Practices" — flags oversized images delivered to smaller display sizes
Most BigCommerce stores find one issue in steps 2–3 (often introduced by a recent theme update or app), and a consistency problem in step 6. Both are fixable in a single afternoon.