Image SEO Checker Online

Open your page in a browser, right-click anywhere and choose View Page Source, then copy the entire HTML or just the section that contains your images. You can also paste just the relevant img tags directly, without the full page HTML. The tool only reads img elements and ignores everything else.

No. The checker only reads literal img elements from the pasted HTML. A picture element's fallback img inside it will still be checked normally, but individual source elements, srcset variants, and images set via CSS background-image are not audited at all, since they're structurally different from an img tag.

Google uses alt text alongside its computer vision algorithms and the surrounding page content to understand what an image shows and what topic it supports. Missing or vague alt text means Google has less signal to classify the image, reducing its chances of appearing in Google Images and weakening the relevance signal it provides to the surrounding page. Alt text also serves screen readers, making it a legal accessibility requirement under laws like the ADA, Section 508 and the European Accessibility Act.

When a browser loads a page, it needs to know how much space to reserve for each image before the image file arrives. Without explicit width and height attributes, the browser renders the page without that space, then shifts the layout when the image loads. This is called Cumulative Layout Shift (CLS) and it is one of Google's Core Web Vitals metrics. High CLS scores hurt both user experience and search rankings.

Lazy loading tells the browser to defer loading an image until it is about to enter the viewport. For images below the fold, this is a significant performance improvement. But the first image on most pages is typically the hero banner or featured image, which is the Largest Contentful Paint (LCP) element. Lazy-loading the LCP image delays the browser from loading the most important visible content, which directly increases the LCP time and hurts Core Web Vitals scores.

Yes, for any image beyond the first. The missing-lazy-load check simply looks for loading="lazy" being absent, it doesn't distinguish between no loading attribute at all and an explicit loading="eager". If you deliberately set eager loading on a below-fold image for a real reason, that suggestion is safe to dismiss, it's a Suggestion severity precisely because the tool can't know your intent.

Search engines use image filenames as one of several signals to understand what an image depicts. Camera-generated filenames like IMG_1234.jpg, DSC_0032.jpg, or Screenshot_2024.png provide zero descriptive context. A filename like red-running-shoes-side-view.webp tells both the search engine and the URL structure something meaningful about the image. Filenames also cannot be changed after upload without breaking URLs and losing any accumulated link value.

No, currently only BMP triggers this suggestion. GIF files are intentionally exempted, because there's no reliable way to tell from markup alone whether a .gif is a genuinely animated image, where GIF is still often the only practical choice, or a static image that was simply saved in an old format. Flagging every GIF risks a false suggestion on legitimate animation. If you know a specific GIF on your page is static, converting it to WebP or AVIF manually is still worthwhile, the checker just won't prompt you to.

No. The entire check runs in your browser using the built-in DOMParser API. Your HTML is never sent to any server. You can disconnect from the internet after the page loads and the checker still works.

No. Checking actual file sizes requires fetching each image URL from a server, which is a network request that browsers block for external URLs due to CORS restrictions. This tool works from HTML alone, which means it can audit the markup attributes but not the files themselves. To check file sizes, use browser DevTools, Google PageSpeed Insights, or WebPageTest.