Glossaire · SEO

Alt Attribute

The alt attribute (alternative text) is an HTML property added to the image tag (img) that describes in words the content and function of an image. It serves two purposes: accessibility, by allowing screen readers to convey the image to visually impaired users, and SEO, by giving search engines textual context they cannot extract from pixels. The alternative text is also displayed when the image fails to load. For Google Images, the alt attribute is a major relevance signal that helps rank visuals on targeted queries. A good alt attribute is short, descriptive, naturally includes the relevant keyword, and avoids stuffing. Left empty for purely decorative images, it becomes essential for visuals that carry information or that are clickable. It is a simple technical element, yet one often overlooked in SEO audits.

The alt attribute is one of the easiest SEO levers to implement, yet one of the most frequently forgotten. It works both for your users and for search engines.

How it works

The alt attribute is added directly in the image's HTML code: <img src="photo.jpg" alt="image description">. When a search engine crawls a page, it cannot "see" the content of an image. The alternative text therefore provides a comprehensible description, used in particular for ranking in Google Images. For screen readers, that same text is read aloud, making your content accessible to visually impaired users.

Key takeaway

An alt attribute should describe the image as it is, concisely (5 to 15 words), including the keyword only if it is naturally relevant.

A concrete example

For a product photo, avoid alt="image1" or alt="shoes shoes running running cheap". Prefer alt="red running shoe for marathon". The description is accurate, readable, and contains useful information. This rigor fits into a broader technical optimization, alongside the title tag or structured data.

Why it matters

When properly filled in, the alt attribute improves your visibility in image search, which accounts for a significant share of organic traffic. It also strengthens your digital accessibility compliance, an increasingly important regulatory concern. Finally, it is a global quality signal valued by search engines. At LUWIZ, we systematically check alt attribute coverage during our technical audits, because this seemingly minor detail often reveals the level of care applied to the entire site.

FAQ

Questions fréquentes

Every informative or clickable image should have a descriptive alt attribute. Purely decorative images take an empty alt attribute (alt="") so screen readers skip them without disrupting navigation.

Yes, when it is relevant and natural. The alt attribute must first describe the image accurately. Including the targeted keyword strengthens ranking on Google Images, but keyword stuffing is counterproductive and harms accessibility.

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