B7 · Performance & Mobile UX

    Image Optimization Checker — are your images slowing the page down?

    Images are usually the heaviest thing on a page — and the easiest big speed win. This check looks at whether your images are optimised: served in modern formats, sized to how they're displayed, compressed, and given explicit dimensions. Oversized, uncompressed images bloat page weight, slow down loading, and cause layout shifts — all of which hurt your speed metrics and the experience.
    Updated June 2026 · Technical SEO & GEO · Part of Performance & Mobile UX

    Check your image optimization

    Paste a URL — GEObubbly checks whether your images use modern formats, are right-sized, compressed and have dimensions set.

    ✓ Free check✓ 1 signal✓ No signup required
    In short: Images are usually the heaviest thing on a page. Compressing them, sizing them correctly and using modern formats is the fastest Core Web Vitals win available.

    What does the image optimization check look for?

    It looks at how your images are delivered and whether they're slowing the page down. Specifically:

    • Modern formats — whether images use efficient formats like WebP or AVIF rather than large legacy JPEG/PNG.
    • Right-sizing — whether images are sized to their display dimensions, not served far larger and scaled down by the browser.
    • Compression — whether images are compressed to a sensible quality rather than shipped at full weight.
    • Dimensions set — whether width and height are declared so images don't cause layout shift.

    Well-optimised images pass; some oversized or unoptimised images is a warning; heavy, unoptimised images significantly slowing the page is a fail.

    How is it evaluated, and how is it scored?

    GEObubbly inspects the page's images for format, size, compression and declared dimensions. It's an extended Performance & Mobile UX check that runs against the page's image assets.

    Why image optimization matters for SEO and GEO

    On most pages, images account for the largest share of page weight, so optimising them is often the single biggest performance win available. Four things matter. Format: modern formats like WebP and AVIF deliver the same visual quality at a fraction of the size of legacy JPEG and PNG. Sizing: serving a 3000px image into a 600px slot forces the user to download many times the data they need, so images should be sized — or served responsively with srcset — to their actual display size. Compression: most images can be compressed substantially with no visible loss. Dimensions: declaring width and height lets the browser reserve space, preventing the layout shift that hurts CLS. The hero image is frequently the LCP element, so optimising it directly improves loading metrics. Lighter images mean faster pages for users, better Core Web Vitals, and a site that's cheaper for crawlers to fetch. Descriptive alt text adds accessibility and image-search value on top.

    How this check scores
    Pass: Images are compressed, correctly sized, and use modern formats with dimensions set.
    Warning: Some oversized or legacy-format images.
    Fail: Large, unoptimized images dragging down Core Web Vitals.

    FAQ

    Optimising images comes down to four steps. First, use a modern format like WebP or AVIF, which are far smaller than JPEG or PNG at the same quality. Second, size images to how they're actually displayed — don't serve a huge file into a small slot — and use responsive srcset to give different sizes to different screens. Third, compress them to a sensible quality, since most images shrink dramatically with no visible loss. Fourth, set explicit width and height so the browser reserves space and the layout doesn't shift as they load.

    Related checks in Performance & Mobile UX

    B5
    Render-blocking resources & page weight
    B1
    Core Web Vitals (LCP, INP, CLS)
    B6
    Lazy-loaded critical content

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