Open a photo

Write a long description for a complex imageExplain charts, maps and diagrams.

For pictures that need more than one sentence: write the full description in the order a listener needs, and have it checked.

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Works with JPG, PNG, WebP, GIF, BMP, TIFF, AVIF and iPhone HEIC photos.

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A writer at a desk comparing a botanical photograph with the braille display beside her keyboard.
Detailed descriptionA home study. A woman at a wooden desk reads a braille display; beside it lie two spiral notebooks and a large print of a white flower.Whole scene first, then the parts

What happens when you open a photo

Charts, diagrams, maps and infographics carry more than one attribute can hold. You write the paragraph that stands in for the whole thing — the page can lay out the measured parts in the right order to start from — and it checks the result for the shape a listener needs, not for the facts inside it.

  • MeasuredColours, light, layout, orientation and the camera's own notes — arithmetic on your pixels.
  • Detected, if you askWhere faces and people are, and what is near or far, by three small models that run on this device. Counted and placed, never identified.
  • YoursThe subject. Nothing here names what is in a photograph, so you do — and every clause after it shows its evidence.

Read where it sits: the picture is decoded by this browser, and neither it nor your words go anywhere.

The grade, running on a sentence

Written by hand

A worked example. The sentence “A woman in a yellow raincoat stands at the end of a wooden jetty, looking out at a flat grey sea.” is typed out a clause at a time and this site’s checker grades it as it goes, finishing at A, 100 out of 100. Nothing read the drawing above it.

What it does

Some images are arguments. A chart with four series, a process diagram with a loop in it, a map with six labelled districts, a scanned form with a structure: the page depends on what is inside them, and no single attribute is going to carry that. The answer is a second piece of text — longer, in the body, available to everyone — and this route is where it gets written and read back.

The ruleset changes shape here. There is no character ceiling worth enforcing, so the length checks turn into structure checks: does the first sentence say what the whole thing is, is any single sentence so long that a listener loses the thread, is the paragraph one sentence pretending to be several. Those are the faults that make a long description hard to follow, and they are invisible on a screen where a reader can scan.

The order of operations

Name the thing

A line chart of rainfall. A floor plan. An organisation chart. One clause, and it is the clause the alt attribute should also carry, because it is what lets someone decide whether to listen to the rest.

Say what it is for

What the page is using it to show. A chart that exists to demonstrate one crossing point should say so before it reads out twelve years of values, because after that sentence the listener knows which number to wait for.

Then the parts, in a stated order

Left to right, largest to smallest, first to last — any order will do as long as you name it and keep to it. A listener who has been told the order can hold their place in it. A listener who has not is being read a list.

What else a file can tell you

A long description answers what the image shows. There is a second set of questions it never touches: when the photograph was taken, on what, at what exposure, whether there is a location in it, whether the caption and credit fields were ever filled in, and whether the file carries a provenance record saying where it came from. None of that is in the picture. All of it can be in the file.

A file’s metadata can hold a great deal: capture data, IPTC caption and credit fields, and, since 2021, dedicated IPTC fields for alt text and an extended description. It is worth looking before you write, because a picture desk that filled in the IPTC caption has already written half of what you were about to. This page reads only the handful a description can use — the date, the camera, and whether the file carries a location at all, never the location itself. Writing your finished alt text and description back into those fields is planned for this site; it is not built yet.

Two things this route will not do

  • It will not read the values off your chart. The Visible text tab can read printed labels and tick text with its Read button, but turning those words into the data a chart shows is a judgement this page does not make; the labels arrive as text for you to place in the description.
  • It will not know which order matters. The structural check can see that your first sentence went straight to detail; it cannot see that you described a flowchart from the bottom up, or that the important series is the third one. Those are judgements about what the image is for, and the page it sits on is the only thing that knows.

Questions people ask

When does an image need more than an alt attribute?

When a reader who cannot see it would still be missing something after hearing the alt text. A photograph of a beach rarely qualifies. A line chart with four series over twelve years always does, because the alt attribute can say what the chart is and cannot say what it shows. The test is not complexity for its own sake — it is whether the page's argument depends on detail inside the image.

Where does the long description go?

On the page, in text, near the image, and reachable by everybody. A details element under the figure, a paragraph in the body, or a link to an anchor further down all work. What does not work any more is the longdesc attribute, which was dropped in HTML5 and was never implemented consistently enough to rely on when it existed.

How should the paragraph be ordered?

Whole first, then parts. Someone listening cannot glance at the shape and then go looking for a number; they get the description in the order you wrote it and cannot scan back. So the first sentence says what the thing is and what it is for, and everything after that fills it in. The checker marks a description that opens on detail, because that is the one structural fault a long description can have.

Should the alt attribute still say something?

Yes, and it should be short. Give the image a name — what kind of thing it is and what it is about — and let the long description carry the content. An empty alt on an image with a long description leaves the image unnamed in the list of things on the page, which is exactly the wrong way round.

Where to take this next

Photographic visual for Describe
In this toolDescribe