Alt text

Alt text, short for alternative text, replaces the image for anyone who cannot see it, which makes it one of the basics of accessibility. The test is simple: if the image disappeared, what words would give a reader the same information? For a photo of a finished kitchen, that might be the style and materials. For a chart, it is the conclusion the chart shows.

Alt text is not a caption, which everyone sees, and not a place to stuff keywords. Not every image needs a description either. Purely decorative images should have an empty alt attribute, so screen readers skip them instead of announcing a file name.

How it works

In HTML, alt text is written inside the image tag as the alt attribute. WCAG success criterion 1.1.1, at level A, requires a text alternative for meaningful non-text content. Screen readers announce the image and read the text, and search engines use it as context for image search and for the page. Most content management systems, including WordPress, offer an alt text field when you upload or insert an image.

Good alt text is concise and specific, usually a sentence or less. It describes what matters in context, so the same photo may need different alt text on different pages. Images that act as links or buttons should describe the destination or action rather than the picture.

You can check your own alt text without special tools. Browsers let you inspect an image to see its alt attribute, and free accessibility checkers list every image that lacks one. A better test is to switch on the screen reader built into your phone or computer and listen to a page: you will hear straight away whether descriptions make sense, repeat the caption or read out file names. Pay particular attention to images that are links, such as logos and product photos.

Example

A landscaping firm's project gallery has twenty photos with alt text such as IMG_4021 or landscaping garden landscaping Munich. Rewritten, one reads: Terraced garden with sandstone steps, box hedging and a lawn on a sloping plot. The header logo, which links to the home page, gets alt text naming the company and the home page, and a decorative leaf pattern gets an empty alt.

Some images need more thought. A before-and-after pair gets alt text describing the change, such as an overgrown back garden before clearing, and the same garden afterwards with new paving and planted borders. A photo containing text, such as a poster for an open day, needs that text in the alt or on the page, because a screen reader cannot read words inside an image. A chart of seasonal bookings gets a one-line summary, with the figures in a table below it.

Why it matters for your business

Missing or poor alt text shuts out blind and low-vision visitors, and accessibility rules in many places treat it as a basic requirement, so it is a common finding in accessibility audits and complaints. It also helps images appear in image search and gives search engines more context about the page. Writing it takes seconds per image at upload; fixing hundreds of images after launch takes far longer, so build it into the publishing routine.

Common mistakes

• Leaving file names or camera codes as the alt text.
• Stuffing alt text with repeated keywords instead of describing the image.
• Starting every description with image of or picture of, which screen readers already make clear.
• Giving decorative images long descriptions instead of an empty alt attribute.

Questions people ask

How long should alt text be?

Usually a short sentence or less is enough. WCAG sets no character limit, but concise descriptions are quicker to listen to and easier to understand. If an image holds complex information, such as a detailed chart, give a short alt text and put the full explanation in the surrounding text or a caption.

Does alt text help SEO?

Yes, modestly. Search engines use alt text to understand images and the pages they appear on, which helps in image search in particular. It is not a place for keyword stuffing, which harms accessibility and looks spammy. Describe the image accurately, and relevant terms will usually appear naturally.

Do all images need alt text?

Every image should have an alt attribute, but not every image needs a description. Meaningful images such as product photos, charts and images that work as links need descriptive alt text. Purely decorative images, such as background patterns or divider graphics, should have an empty alt attribute so screen readers skip them.