Alt text (alternative text) is an HTML attribute applied to <img> tags that provides a textual description of an image. It serves two critical purposes: accessibility — screen readers read alt text aloud to visually impaired users, allowing them to understand image content; and SEO — search engines use alt text to index and rank images, helping your content appear in Google Image Search. Without alt text, you miss out on valuable organic traffic and create a poor experience for users relying on assistive technology.

When the alt attribute is completely missing, screen readers may read the image filename (e.g., "DSC_00421.jpg") — which is often meaningless and frustrating for users. Search engines also lose context about the image, potentially harming your rankings. A missing alt attribute is considered an accessibility violation under WCAG 2.1 guidelines (Success Criterion 1.1.1). Every <img> tag should have an alt attribute, even if it's empty for decorative images.

Redundant alt text includes generic placeholder phrases like "image", "picture", "photo", "graphic", or auto-generated names like "image001". These descriptions add no value because they don't describe the content of the image. A screen reader user already knows it's an image. Instead, describe what the image actually shows — e.g., use "Golden retriever playing fetch in a sunny park" instead of "dog photo". Our linter automatically flags these common redundant patterns.

Decorative images (spacers, background flourishes, dividers) should use an empty alt attribute: alt="". This tells screen readers to skip the image entirely, keeping the experience clean. Note the difference: alt="" (empty, intentional) is not the same as a missing alt attribute (which is an error). Our tool distinguishes between these two cases — empty alt is marked with a blue info tag, while missing alt is flagged as a red error.

There's no hard technical limit, but best practice recommends keeping alt text under 125 characters. Many screen readers pause or truncate around this length. More importantly, alt text should be concise yet descriptive — aim to convey the essential information in one short sentence. For complex images (charts, infographics), use a brief alt summary and provide a longer description elsewhere (e.g., in a <figcaption> or adjacent paragraph). Our linter flags alt text exceeding 125 characters with a yellow "Too Long" warning.

The alt attribute is used by screen readers and displayed when an image fails to load — it's essential for accessibility and SEO. The title attribute, on the other hand, typically appears as a tooltip on mouse hover and is not read by most screen readers by default. While title can provide supplementary information, it should never replace alt text. Always prioritize writing good alt text; the title attribute is optional and secondary.

For bulk checking, you can use our Paste HTML method with HTML from multiple pages, or use automated crawling tools like Screaming Frog SEO Spider, Sitebulb, or Google Lighthouse. These tools can crawl entire sites and report missing/empty alt attributes at scale. Our online linter is ideal for quick spot-checks on individual pages, templates, or HTML snippets during development.

Yes, indirectly. While alt text is not a direct ranking factor for web pages, it significantly impacts image search rankings. Well-described images can drive substantial organic traffic from Google Images. Additionally, alt text contributes to overall page relevance and accessibility signals, which align with Google's E-E-A-T guidelines. Poor accessibility may also increase bounce rates from users who can't engage with your content, indirectly affecting rankings.