Image SEO Guide: Alt Text, File Names, Slugs & Captions

Images can bring steady traffic from Google Images and Lens — for product pages, recipes, real estate, jewellery and travel especially. But search engines understand images mainly through the words around them. This image SEO guide covers the parts you control: alt text, file names, slugs, captions and page context.

How search engines understand an image

Google uses several signals together: the page title and headings, the text near the image, the alt attribute, the file name, captions and structured data. Computer vision helps, but context still decides which searches your image appears for. That is why the same photo can rank on one page and not on another.

Alt text: describe, don't stuff

Alt text is read aloud by screen readers and shown when an image fails to load. Write it for a person who cannot see the image:

• Keep it to one short sentence — usually 8–15 words.
• Include the key subject and, when natural, the keyword the page targets.
• Decorative images (dividers, background shapes) should use empty alt: alt="".
• Never repeat the same alt text on every image.

File names and slugs

Google notes that file names can give light clues about an image's subject. Rename before uploading:

• IMG_20260812_1042.jpg → gold-jhumka-earrings-22k.jpg
• Use lowercase and hyphens, not spaces or underscores.
• Keep it short: 3–6 meaningful words.

Page context matters most

• Place important images near related headings and text.
• Use captions where people actually read them (galleries, articles, product details).
• Make sure the page itself targets a clear topic — an image cannot rank for something the page is not about.

Technical basics

• Use real <img> elements for important images, not CSS backgrounds, so they can be indexed.
• Modern formats: WebP or AVIF with sensible compression.
• Set width and height to prevent layout shift.
• Lazy-load images below the fold with loading="lazy", but not the main hero image.
• Responsive images with srcset so phones get smaller files.
• Image sitemap or include images in your normal sitemap for large galleries.
• Structured data (Product, Recipe, Article) helps rich results show your images.

Writing alt text for hundreds of images

An online store or stock library can have thousands of images. The AI Image SEO Metadata Generator drafts alt text, SEO titles, slugs and meta descriptions for each image in a batch and exports a CSV you can import into your CMS. Always review AI output — but editing a good draft is far faster than writing from scratch.