Alt Text: What It Is and How to Write It for SEO

Alt text (short for alternative text) is the HTML attribute that describes an image’s content in words. Screen readers read it aloud for visually impaired users, and search engines use it to understand what an image shows since they cannot see pixels the way people do. It lives in the code as alt=\"description\" inside the image tag and does not appear on the page unless the image fails to load.

For a local service business, alt text is often the only way Google connects a photo of a finished job to the words a customer might search. It also affects image seo rankings in Google Images and contributes, in a small way, to overall on-page seo quality.

How alt text works

Alt text works as a text substitute that loads instead of the image and gets read by assistive technology and crawled by search bots. It sits inside the img tag as an attribute, separate from the file name, caption, or surrounding text.

When an image can’t display, whether from a slow connection or a broken link, the browser shows the alt text in its place. Screen reader software reads it aloud so blind and low-vision users get the same information a sighted visitor gets from looking at the picture. Google’s crawler also reads this text to classify the image and decide whether it’s relevant to a search query.

Why alt text matters, and what it doesn’t do

Alt text matters for accessibility compliance, image search visibility, and giving Google more context about a page’s topic. It does not act as a ranking shortcut for the main page, and stuffing keywords into it can hurt rather than help.

Google has said image alt text is one of several signals used to understand an image, alongside the surrounding text and the page title. It won’t move a page from position 10 to position 1 on its own, but across dozens of images on a site it adds up, especially for businesses that rely on photo-heavy pages like before-and-after galleries.

Alt text vs. image title vs. caption

Alt text, the title attribute, and a visible caption are three separate things that often get confused. Alt text is for accessibility and search context, the title attribute shows a tooltip on hover, and a caption is visible body text near the image.

Good vs. bad alt text

Good alt text describes the specific image accurately and concisely. Bad alt text is either blank, stuffed with repeated keywords, or generic filler like \”image1.jpg.\”

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How to check alt text on a website

Check alt text by inspecting page elements in a browser, running a site crawl, or reviewing the Images report in Google Search Console. Right-click an image and choose Inspect to see the alt attribute directly in the code.

A site crawler such as Screaming Frog will list every image on a domain along with any missing or duplicate alt text in one export. For a quick manual check on a handful of key pages, browser inspection is faster than exporting a full crawl.

Mistakes and myths about alt text

A common myth is that alt text is an old, deprecated tag that no longer matters. It’s still part of the HTML standard and still read by every major screen reader and crawler in use today. Another myth is that alt text needs to include the exact target keyword; describing the image accurately is more useful than forcing a phrase that doesn’t match what’s shown.

How to improve alt text

Fixing alt text across a site is usually quick, but doing it well across hundreds of images takes a system.

1. Audit existing images. Run a crawl or export the Search Console Images report to find pages with missing or empty alt attributes.
2. Write descriptions, not keyword lists. Describe what’s actually in the photo in one short sentence.
3. Keep it under about 125 characters. Screen readers cut off or struggle with long strings.
4. Skip decorative images. Use an empty alt=\"\" for purely visual elements so screen readers skip them.
5. Re-check after a redesign. Alt text often gets stripped when images are re-uploaded to a new CMS or theme.

For the full walkthrough with examples by image type, see how to optimize images for search.

Related terms

Image SEO covers file names, compression, and formats alongside alt text.

On-page SEO is the broader category alt text falls under.

Meta tags are other HTML attributes that inform search engines without appearing on the page.

User experience (UX) benefits from alt text through better accessibility.

FAQ

Does alt text need to include a keyword?

Only if the keyword genuinely describes what’s in the image. Forcing an unrelated keyword into alt text reads as spam to both users and search engines, and can trigger quality flags.

What happens if alt text is left blank?

Screen readers either skip the image or read the file name aloud, which is often unhelpful. Search engines lose a signal about the image’s content, which can hurt visibility in image search.

Does alt text apply to background images in CSS?

No. CSS background images don’t have an alt attribute because they’re treated as decorative. Content images that convey information should use an actual img tag with alt text.

How long should alt text be?

Aim for roughly 125 characters or fewer. Longer descriptions can get cut off by screen readers and rarely add useful information beyond that length.