The essentials
- Indexing: Google has to be able to discover the image's URL (an img tag or a sitemap), download it (no robots.txt block) and connect it to an indexed page.
- Ranking: the text around the image (alt, caption, page title, context) does most of the work; Google also recognises the visual content.
- Frequent traps: badly implemented lazy loading, images as CSS backgrounds, a blocked CDN, unsupported formats, images duplicated across sites.
- Checking: Search Console, the Performance report filtered on "Image", and URL inspection.
Google Images accounts for a significant share of searches, and for visual trades (interiors, crafts, property, restaurants, e-commerce) it is a source of qualified traffic. Yet many sites have images invisible to Google, because of one technical detail. This article describes the indexing process, the conditions to meet and the signals that lift an image, with a checklist and the verification method.
How Google indexes an image
- Discovery: Googlebot finds the image's URL in the page's HTML (an
<img src>,<picture>tag, asrcsetattribute) or in an image sitemap. - Crawling: Googlebot-Image downloads the file, if robots.txt and the HTTP headers allow it (see HTTP response codes).
- Association: the image is connected to its host page; it is that page's text and the image's own that determine which queries it appears on.
- Analysis: Google recognises the visual content (objects, places, text, faces) and detects duplicates.
- Indexing: the image is available in Google Images and, possibly, in enriched web results (thumbnails, Discover).
An image is never indexed on its own: with no indexed host page, it doesn't exist for Google. Check your pages' indexing first, described in indexing in Search Console.
The technical conditions
| Condition | Check | Fix |
|---|---|---|
| The image in the HTML | View the source: the img tag is present without JavaScript | Avoid CSS-only images background-image for important visuals |
| No blocking | robots.txt blocks neither the images folder nor the CDN; the X-Robots-Tag: noindex header is absent | Allow Googlebot-Image; check the CDN's robots.txt |
| Compatible lazy loading | Off-screen images have a real src or the native loading="lazy" | attribute src Replace scripts that leave |
| empty with native lazy loading | A supported format | JPEG, PNG, WebP, AVIF, GIF, SVG, BMP |
| Convert exotic formats; WebP or AVIF for weight | A stable URL | The image's URL doesn't change at every deployment |
| Avoid hashes in the filenames of content images | Attributes width and height Dimensions declared | present |
| Add them: it stabilises the layout (Core Web Vitals) | An image sitemap image:image The sitemap contains | tags or a dedicated sitemap |
The signals that rank an image
- Generate it through the CMS or an SEO plugin The alt attribute:
- a factual description of the image, in one sentence, with the subject and, where relevant, the place. Not a list of keywords. Alt text also serves accessibility. The filename:
- descriptive, in lower case, words separated by hyphens. The caption and the nearby text:
figcaption. - Google reads the paragraph surrounding the image and the The page's title and subject:
- an image of a renovated kitchen in a page about "kitchen renovation in Nantes" ranks on that query. Quality and originality:
- large, sharp, unique images are favoured; stock images are deduplicated in favour of the original source. the
imagepropertyImageObject. - property in Article, Product, LocalBusiness, Recipe; the licence through pages that are slow because of heavy images are penalised; compress and serve appropriate dimensions through
srcset.
For local SEO, these signals combine with the listing's photos; the specifics are in geotagging your images.
Checking your images are indexed
- Search Console, the Performance report: search type "Image". You see the queries, the pages and the impressions; a site with visible images and zero Image impressions has a technical problem.
- URL inspection on a page: the screenshot and the rendered HTML show whether the images are loaded by Googlebot.
- A
site:votredomaine.frsearch in Google Images: a preview of the indexed images. - A crawler (Screaming Frog): lists the images, missing alt text, excessive weights and blocked images; see Screaming Frog.
A compliance checklist
| Action | Priority |
|---|---|
| Unblock images in robots.txt (site and CDN) | Immediate |
| Replace script-based lazy loading with the native attribute | Immediate |
| Fill in alt text on every content image | High |
| Convert to WebP, compress, declare width and height | High |
| Add an image sitemap | Medium |
| Mark up images in the structured data | Medium |
| Replace stock images with original photos | Ongoing |
How GreenRed helps
Rather than juggling several tools, GreenRed's Site health module brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
Why don't my images appear in Google Images?
The most frequent causes: a robots.txt blocking the images folder or the CDN, lazy loading that leaves src empty until the user scrolls, images as CSS backgrounds, or a host page that isn't indexed. URL inspection in Search Console shows what Googlebot sees.
Do you need an image sitemap?
It is useful if the images are loaded by JavaScript, if the site is large, or if some images aren't connected to easily crawlable pages. For a brochure site with images in the HTML it isn't essential, but it speeds up discovery.
Is WebP indexed properly by Google?
Yes, WebP and AVIF have been supported by Google Images for several years. They cut weight by 25 to 50% against JPEG, which improves speed and therefore page ranking.
How long does indexing an image take?
Generally longer than the page: from a few days to several weeks, since Google crawls images at a lower priority. An image sitemap and a well internally-linked page speed the process up.