Image SEO: Alt Text, File Names, and Why Google Can't See Your Photos

Alt text (short for alternative text) is an HTML attribute added to the <img> tag that describes what an image shows:

Alt text serves three purposes:
1. Accessibility: Screen readers read alt text aloud for visually impaired users. This is why alt text is legally required in many countries for public websites.
2. SEO: Google uses alt text to understand image content and include images in relevant Image Search results.
3. Fallback: If the image fails to load, the browser shows the alt text instead, so users know what was supposed to appear.

Good alt text is descriptive and specific — it tells a blind person (or a search engine) exactly what the image shows in context.

Bad alt text examples:
- alt="" — empty (fine only for purely decorative images)
- alt="image" — useless
- alt="photo1" — filename, not description
- alt="red ball dog puppy golden retriever grass garden sunny day backyard" — keyword stuffing

Good alt text examples:
- alt="Golden retriever puppy playing with a red ball in a sunny garden"
- alt="Chart showing monthly website traffic growth from January to June 2024"
- alt="Close-up of sourdough bread crust with an open crumb structure"

Rules of thumb:
- Be specific and descriptive (aim for 5–15 words).
- Include your keyword naturally if it's genuinely relevant to the image.
- Don't start with "image of" or "photo of" — Google already knows it's an image.
- Purely decorative images (dividers, background shapes) should have alt="" (empty, not missing).

Before an image even reaches the page, its file name is a signal. Compare these two URLs:

• /uploads/IMG_4827.jpg — tells Google nothing
• /images/golden-retriever-puppy-playing.jpg — tells Google exactly what it is

When Google crawls a page and encounters an image, the file name (part of the URL) is one of the first signals it reads to understand the image's subject.

File name best practices:
- Use descriptive, lowercase words separated by hyphens.
- Include a relevant keyword if it accurately describes the image.
- Keep it concise — 3 to 5 words is ideal.
- Never use spaces or underscores (hyphens are the SEO standard separator).

In many countries, providing alt text on meaningful images is a legal requirement under accessibility laws:

• USA: Section 508 of the Rehabilitation Act, ADA Title III
• EU: European Accessibility Act (coming into force 2025)
• UK: Public Sector Bodies Accessibility Regulations

Beyond the legal risk, missing alt text is a real barrier for users with visual impairments. Every image that matters should have descriptive alt text.

The only exception: Decorative images (visual dividers, background patterns, purely aesthetic elements) should use an empty alt attribute alt="" — not a missing alt attribute. An empty alt tells screen readers to skip the image entirely, which is the correct behavior for decoration.

The title attribute on images shows as a tooltip when a user hovers over the image:

Image titles have minimal direct SEO impact, but they can add context and improve user experience. They're optional, but good practice for images where additional context adds value.

Don't duplicate the alt text in the title — they serve different purposes. Alt text is what the image shows; title can add a supplementary fact or caption.

Image size and compression: Large uncompressed images slow down page load. Slow pages rank worse. Compress images using tools like Squoosh, TinyPNG, or convert to WebP format (30-40% smaller than JPEG at equivalent quality).

Lazy loading: Adding loading="lazy" to images below the fold reduces initial page load time:

srcset for responsive images: Serve different image sizes to different screen sizes to avoid loading 2000px images on mobile phones.

Structured data for images: Adding ImageObject schema helps Google understand images in context, especially for recipes, products, and articles.