How do I write an extended description for a complex image?
Quick answer
Use two levels: a short description that identifies the image and points readers to the longer description, followed by an organized account of its essential information. For the long version, describe only what is visible or supplied, and arrange details and relationships so readers can follow them. Headings or tables can help structure the longer account. [S1]
The question, the details, the next step.
How do I know when an image needs an extended description instead of one sentence?
Use an extended description when a short phrase or sentence cannot convey the image’s substantial information. Think of the two parts as doing different jobs: the short description identifies the image and, when appropriate, directs readers to the longer account; the longer account represents the image’s essential information. [S1]
Start by listing what a reader would need to understand from the image: its main elements, their labels if visible, and the relationships or sequence shown. If that list is too substantial to fit clearly in a sentence, organize it as a long description. Do not add an interpretation simply because it seems likely. Stick to details actually visible or supplied in the demonstration material. [S1]
What should go in each part, and how can I keep the short version from repeating the long one?
Give each part a distinct purpose. The short description names the image and signals that a detailed description follows or is available. It should not try to compress every label, value, or relationship into one crowded sentence. The long description carries the relevant detail, in a sequence a reader can follow. Making that detail available to everyone is recommended by W3C. [S1]
A reusable two-level template:
- Short description: “ [Image type or subject], with a detailed description below.”
- Long description:
- Overview: Identify what the image presents.
- Details: Describe its visible parts, labels, values, or stages in a sensible order.
- Relationships: Explain visible connections, comparisons, or sequence without inferring causes or meanings not shown.
Use only the sections that fit the image. Headings can help readers navigate the detail; a table may help when the image presents information in a clear row-and-column pattern. [S1]
Can you show the structure with a sample, without pretending it describes a real image?
Here is a hypothetical example. Assume the supplied demonstration image shows three labeled boxes connected from left to right by arrows. The labels are “Collect,” “Sort,” and “Share.” This example uses only those stipulated details; it does not assume what is collected, who sorts it, or what gets shared.
Short description: “A three-step flow diagram; the detailed sequence is described below.”
Long description: “The diagram contains three labeled boxes arranged from left to right. The first box is labeled ‘Collect.’ An arrow points from it to a box labeled ‘Sort.’ A second arrow points from ‘Sort’ to the final box, labeled ‘Share.’ The image presents these labels in that order.”
The short version identifies the image and points to detail. The long version states the visible arrangement and direction of the arrows. If a real image includes other important visible elements—such as a title, legend, or branches—include them when supplied; do not fill gaps with guesses.
What should I check before I publish the description?
Compare the description with the image or the supplied demonstration material, detail by detail. Check that every statement is supported, that important relationships are stated plainly, and that the short description and long description do not contradict each other. If a value, label, or connection is unreadable or absent from the supplied material, do not invent it; leave it out or mark it for clarification. The source guidance supports organizing substantial information and making the detailed account available, but it does not prescribe one universal length or exact wording. [S1]
A practical checklist
Decide whether one short phrase or sentence can convey the image’s substantial information.
Write a short identifier that points to the longer description when appropriate.
Organize the long description around the image’s essential visible details and relationships.
Use headings or a table when they make the information easier to follow.
Check every detail against the image or supplied material; remove unsupported inferences.
Confirm that the short and long descriptions agree.
A few more useful answers
Should the long description repeat the short description?
It can restate the image’s subject briefly for context, but its main job is to provide the essential detail that the short description leaves out.
Can I explain what a diagram means, not just what it shows?
Describe visible relationships, labels, and sequence, but do not present an inferred cause, purpose, or conclusion as a visible fact. Ask for clarification if the intended meaning is needed and not supplied.
Do all extended descriptions need headings or a table?
No. W3C notes that headings and tables can help structure a detailed description; choose a format that suits the information shown. [S1]
Sources
References used for this guide.
- [S1] Complex Images: Short and Long Text Alternatives w3.org · Checked