Image alt text

What image alt text is

Alt text is the written description attached to an image in the code of a page. A screen reader reads it aloud in place of the picture, a browser shows it when the image fails to load, and a search engine reads it because it cannot see the image itself. It is a sentence or a phrase, and it belongs to the image, not to the page.

It is not a caption. A caption is visible to everyone and adds something to the picture; alt text replaces the picture for someone who cannot see it. It is also not a place to put keywords. An image described as “plumber Kelowna emergency plumber hot water tank” is read aloud, word by word, to a blind visitor, and it is obvious to a machine as well.

This is the site-wide version of the job. The alt text writing service in the editing pillar is the careful one: documents, reports, charts, diagrams and photographs where the image carries information that has to be reconstructed in words. This is the batch: every image on a website, sorted, described or deliberately left empty, and handed back as a sheet.

When you need it

You need it when nobody has ever filled these in, which is the normal state of a small business website. Images get uploaded from a phone or a stock library, the field is left blank, and after five years there are four hundred of them.

The second case is a legal or contractual one. If you sell to government, to a school board, to a health authority or to a large company, an accessibility requirement is probably already in your contract or in your province's rules, and missing alt text is the first thing an audit finds because it is the easiest thing to count.

The third case is a shop. Product images with filenames like IMG_4471 and no description are invisible to image search, and image search is one of the ways shoppers arrive at a product. That work overlaps with product descriptions and is usually done in the same pass.

You do not need this for a site of twenty pages with thirty images. Write them yourself in an afternoon; the rules below are the whole method.

What gets written

• Descriptions for images that carry meaning. A photograph of your own work, a team portrait, a product, a map, a screenshot of a form. Written to say what a sighted reader gets from it, in the fewest words that do the job.
• Empty alt text for images that do not. Background textures, dividers, decorative icons beside a heading that already says the word. These get an empty alt attribute, deliberately, so a screen reader passes over them in silence. This is the correct answer and almost nobody gives it.
• Function, not appearance, for images that do something. A logo that links to the home page is described by where it goes. An icon that is a button is described by what the button does.
• Text inside images, transcribed. Posters, price lists and infographics saved as pictures. If the words exist only inside the image, they exist for nobody else.
• The ones that need you. A short list of images I cannot describe without knowing what they show: an unlabelled piece of equipment, a face, a site nobody named. You answer those in a single pass.

The search benefit is real and it is second. Described images can appear in image results and give a page a little more to be understood by, which matters on a shop. But the reason to do it is that a person using a screen reader is currently being read a list of file names.

What you get

The alt text sheet. One spreadsheet, one row per image: the page it sits on, a thumbnail or the file name, the current alt text if any, and the new text. Empty ones are marked as deliberately empty, not left blank, so nobody helpfully fills them in later.

The decorative list. A separate tab of every image classed as decorative, with a one-line reason, so you can disagree with any of them before it is applied.

The house rule. One page telling whoever uploads images what to write, with four or five examples from your own site, including the cases where the answer is nothing at all.

A worked example

An illustration. A Guelph landscaping company has a hundred and ten pages carrying about six hundred and forty images, nearly all of them photographs of finished jobs, uploaded straight from a phone. Fourteen have alt text, all of it the file name. The company has begun bidding for municipal grounds contracts and the tender documents ask about accessibility conformance.

The pass classes about two hundred images as decorative: repeated leaf motifs, dividers and the same three icons used throughout the template. Those get empty alt text, and fixing the template handles most of them in one change. Around four hundred job photographs get descriptions naming what was built and where the picture is taken from, which is what a reader wants and what an image search matches. Sixty-odd are set aside for the owner, because only he knows which are his own work and which came from a supplier's library. The house rule runs to one side of paper, and the crew member who posts the weekly photographs now writes the line himself.

How it runs

1. A half-hour call. How many images you have, whether any of this is contractual, and who uploads pictures week to week. No charge.
2. A fixed price in writing. Priced per image band or per page, agreed before anything starts.
3. The crawl. Every image on the site pulled into one sheet with its page and its current alt text. Template images show up at once, because they repeat.
4. The writing. Six hundred images take about two weeks, decorative classification first so the template change can go live early. You answer the short list of images only you can identify.
5. Delivery. The sheet, the decorative list and the house rule, applied by you or by me as metadata entry.

What it costs

Quoted as a fixed price in CAD after the half-hour call, because the count of images varies far more than the count of pages. Sites built on a template are cheaper than they look, since one fix covers hundreds of decorative images. Shops with a photograph per variant are dearer. The pricing page shows the four published ways of working, and the number is fixed in writing before anything starts.

What happens next

Alt text is one of three things an accessibility check looks at, and the other two are usually next: heading structure so a screen reader can navigate the page, and descriptive link text so a list of links is not forty instances of the phrase “read more”. Where you have charts, reports or diagrams rather than photographs, the editing-pillar version describes them properly, one at a time. This piece of work is complete on its own, and nothing further is assumed.