Text Alternative
Definition
WCAG states the principle in success criterion 1.1.1 Non-text Content, at Level A: all non-text content presented to the user has a text alternative that serves the same purpose. The phrase 'same purpose' is doing the work. The alternative is not a description of appearance; it is whatever the content was there to convey. A control gets text naming its function; a chart gets the finding it shows, with a route to the underlying numbers. Time-based media gets at least a descriptive label, with the fuller requirements living under guideline 1.2. A test or puzzle that must stay non-text, such as a CAPTCHA, needs a version aimed at a different sense. And content that is purely decorative is marked so assistive technology can ignore it.
Why It Matters
Alt text is one place a text alternative goes, but it is not the only one. The same principle governs the accessible name of an icon button, the caption file beside a video, the transcript under a podcast, the figcaption beneath a diagram, the data table next to a chart, and the text layer inside a tagged PDF. Text has a second property worth the trouble: it can be searched, indexed, translated, resized, read aloud in a car, and rendered on a braille display. A number baked into a PNG exists nowhere else. Publish a quarterly chart as an image with no alternative and the figure is invisible to a search engine, unusable to a screen reader, and lost to anyone who copies the page into a document.
How It Works
Work out which of four kinds of content you have, then act accordingly. Decorative content is given an empty alt or hidden with aria-hidden, so nothing is announced. Functional content — an icon that is a link or a button — is named by its action, such as 'Download the 2025 accounts'. Informative content gets a short equivalent, usually a sentence. Complex content such as a chart, a floor plan or a map gets two things: a brief alternative that says what it is, and a long description close by in real text — a paragraph, a table, or a link to a page holding the figures. For media, the alternative is a set of files: a captions track alongside the video, and a transcript on the page.
Real-World Example
An agency publishes an annual report at report-2025.99helpers.site with three charts exported as PNGs. Each image gets a one-line alt naming the trend, such as 'Bar chart: donations rose from 412,000 to 538,000 pounds between 2023 and 2025'. Underneath each chart sits a small HTML table with the same numbers, which takes about a hundred bytes per row and doubles as content a search engine can read. 99helpers serves the images and the page as static files; it does not read a chart and generate a description for you, so the alternatives are written once at authoring time and travel with the HTML.
Common Mistakes
- ✕Describing how a graphic looks rather than what it is for — 'blue circular icon' tells a listener nothing, while 'Play the demo' tells them everything
- ✕Cramming a full chart description into the alt attribute — a long alternative belongs in visible text or a table beside the image, where sighted readers benefit too
- ✕Assuming a text alternative is only for images — audio, video, icon fonts, CSS background graphics and PDF page scans all need one as well
Related Terms
Alt Text
Alt text is the alt attribute on an HTML image: a short written replacement for the picture, read aloud by a screen reader and shown when the image fails to load. A decorative image takes an empty alt, not a missing one.
Captions
Captions are time-synchronised text for a video's audio: the dialogue, who is speaking, and any sound that carries meaning. They are not subtitles, which assume the viewer can hear and only translate the words.
Transcript
A transcript is the full text of an audio or video recording, written out as a document rather than tied to the timeline. For audio-only content it is the text alternative; for video, a descriptive transcript also covers what is shown on screen.
Accessible PDF
An accessible PDF is one that assistive technology can read out in a sensible order, because it carries a hidden structure of tags alongside the visible page. A scanned page saved as a PDF is a picture of text and carries none of that.
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