Alt text is one of those small details that punches far above its weight. A single well-written sentence per image makes your site usable for blind visitors, helps Google understand what your pictures show, and can even pull traffic from Google Images. Yet most sites either leave alt text blank or fill it with keyword-stuffed nonsense that helps no one.
Writing good alt text is not complicated once you know the principles. This guide covers what alt text actually does, the rules that separate good from bad, when to leave it empty, and how to use keywords without crossing into stuffing.
The alt attribute was created for accessibility. When a screen reader encounters an image, it reads the alt text aloud so visually impaired users know what is on the page. If an image fails to load, browsers display the alt text in its place. These are its primary jobs, and SEO benefits flow from doing them well.
For search engines, alt text is one of the strongest signals about an image's content. Google cannot interpret a photo the way you can — it leans on your description, the file name, the caption, and the surrounding text to decide what the image shows and when to surface it in image search. Clear, honest alt text feeds that understanding directly.
There is also a legal and ethical dimension. In many regions, accessibility is a legal requirement for commercial sites, and alt text is one of the easiest compliance wins. Writing it well serves real people first and rankings second — which is exactly how Google wants you to think about it.
Good alt text follows a handful of simple rules. Internalize these and you will write better descriptions than the vast majority of sites:
Examples make the difference concrete. Here is the same image described three ways:
alt="shoes" — technically present, but useless. Which shoes? Doing what?alt="buy cheap running shoes best running shoes discount running shoes sale" — keyword stuffing. It reads terribly in a screen reader and can draw a spam penalty.alt="Pair of red trail running shoes with muddy soles on a forest path" — specific, natural, and genuinely useful to someone who cannot see the photo.Notice that the good version includes a plausible keyword phrase ("trail running shoes") without repeating it or contorting the sentence. That is the balance you are aiming for every time: describe first, and let relevance follow.
For functional images, describe the function. A search button showing a magnifying glass gets alt="Search", not alt="magnifying glass icon". A linked logo gets the company name. The test is always the same: if you could not see the image, would this text give you what you need?
Not every image deserves a description. Decorative images — background textures, divider flourishes, stock flourishes that add no information — should get an empty alt attribute: alt="". This is not the same as missing alt text. An empty attribute tells screen readers to skip the image silently, which is exactly what you want for decoration.
Leaving alt text off entirely is different: it forces some screen readers to read out the file name instead, which is the worst possible outcome. The rule is simple — informative images get real descriptions, decorative images get alt="", and no image gets a missing alt attribute. If you are auditing a site and find images with no alt attribute at all, those are your first fixes.
Keywords do belong in alt text — sparingly and honestly. If your page targets "trail running shoes" and the photo shows exactly that, using the phrase once in the description is natural and helpful. The problem starts when every image on the page repeats the same keyword, or when descriptions get padded with keyword lists that describe nothing.
Google treats alt text stuffed with keywords the same way it treats stuffed body copy: as a spam signal. One honest mention per image is plenty. Vary your phrasing across images the way you would in normal writing, and never sacrifice clarity for keyword placement.
If you are unsure whether you have overdone it, paste your page copy into a keyword density checker and review the numbers. While the tool analyzes visible text rather than alt attributes, a page that reads as stuffed in the body usually has stuffed alt text too — it is a useful proxy for the same bad habit.
Alt text works best as part of a complete image optimization package. Search engines combine multiple signals, and each one reinforces the others:
red-trail-running-shoes.jpg instead of IMG_4829.jpg.Alt text is also worth checking alongside the rest of your on-page elements. Our meta tags analyzer reviews your titles, descriptions, and headings in one pass — pair it with an image audit and you cover the core on-page checklist in minutes.
One more practical note for content creators: if you publish posts about YouTube videos, you will often work with thumbnail images. Our guide on how to download YouTube thumbnails walks through grabbing them, and every thumbnail you reuse deserves the same thoughtful alt text treatment as any other image.
Before you hit publish, run each image through this checklist:
Make this a publishing habit rather than a cleanup project. Writing alt text takes ten seconds per image at publish time and hours per hundred images when you do it retroactively.
Yes. Alt text helps search engines understand image content, which supports image search rankings and reinforces the page's topical relevance. Its primary purpose is accessibility, but the SEO benefit is real — especially for image-heavy pages like product listings and tutorials.
Keep it under about 125 characters. Most screen readers begin truncating beyond that point, so longer descriptions get cut off for the very users alt text exists to serve. If an image genuinely needs a longer explanation, put the detail in the surrounding text or a caption instead.
No. Include a keyword only where it describes the image honestly, and never repeat the same keyword across every image on the page. Keyword-stuffed alt text reads badly for screen reader users and can be treated as a spam signal by search engines.
Alt text is read by screen readers and used by search engines; the title attribute shows a tooltip on hover and is ignored by most screen readers. Alt text is the one that matters for accessibility and SEO. You can skip title attributes entirely in most cases.
They need an empty alt attribute (alt=""), not a description and not a missing attribute. The empty attribute tells assistive technology to skip the image. A missing alt attribute is worse — screen readers may fall back to reading the file name aloud.
Alt text is a small effort with an outsized return: better accessibility, clearer signals for Google, and a shot at image search traffic. Describe each image honestly, keep it short, use keywords only where they fit, and audit your pages with our free meta tags analyzer to keep the rest of your on-page SEO in shape.
