Wikipedia:Alternative text for images
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This page is part of the Manual of Style, and is considered a guideline for Wikipedia. The consensus of many editors formed the conventions described here, and Wikipedia articles should heed these guidelines. Before making any major changes to these guidelines, please use the discussion page to ensure that your changes reflect consensus. |
Every time a Wikipedia article uses an image, the alternative text for that image should be specified. Alternative text is used as a replacement for an image, whenever the image cannot be seen. This can happen, for example, when someone:
- uses a speech browser (e.g. a visually impaired person)
- uses a text-only browser (e.g. browsing from a mobile phone)
- uses a graphical browser with images turned off
- has not yet downloaded the image
- browses results from a Web search
- fails to download by an erroneous wire
- copies an extract from a Web page into a word processor.
Alternative text is also used in other circumstances: for example, Google's image search uses it to help return appropriate images. Finally, good choice of alternative text and captions makes life easier for people who are viewing the source of an article, either when editing it, or in a diff, or in Wikipedia's internal search.
You can use [[Image:source-of-image|alternative text goes here]] to specify alternative text. See Wikipedia:Extended_image_syntax for other possible frame, link and other options available with images and Wikipedia.
It can be difficult choosing appropriate alternative text, though. It has to sound good in a speech browser; it should make sense in a graphical browser with images turned off; it should fit with the surrounding text when viewed with a text-only browser—trying to accommodate all of these can be quite daunting! This article should make the whole process a little easier.
[edit] Conflict between caption and alt text
Unfortunately, the image syntax has no way of specifying alt text that is different from the caption. Therefore, if the image has a caption, please follow the advice in Wikipedia:Captions to choose an appropriate caption, and don't worry about the alt text (which will automatically be made the same as the caption). If the image does not have a caption, then follow the advice on this page to choose the most appropriate alt text.
[edit] Imagine you're writing for an audio cassette
A helpful way to think about alternative text is to imagine that the Web page text, including all alternative text, is the script for an audio cassette. Your listeners aren't necessarily blind, so they may be interested in hearing about what something looks like. But they can't possibly see any images on the cassette, and they never will, so referring to an image itself will sound silly. If you write your alternative text with this in mind, it should work well in all the situations listed above.
[edit] Choosing good alternative text
Alternative text should serve as a replacement for the information or meaning conveyed by the image. It isn't there to describe what the image looks like, or to tell us information about the image format. In choosing a phrase to use for the alternative text, think about what the image expresses.
In encyclopedia articles, images are often used to convey information in an intuitive way. Many times, this information is best expressed as an image, rather than as text, but as noted above, there are situations where the image itself is not available. In these situations, the alternative text is usually used in place of the image.
The alternative text should communicate the same information that the image communicates. If the image is there to convey information about color, then mention the color in the alternative text. If the image is there to convey something about shape or size, then mention that in the alternative text. Don't try to describe every detail of the image, but do endeavour to summarize the image's intent in a way that will make sense to someone who cannot see the image.
[edit] The best alternative text is often nothing
In Wikipedia, images tend to be fairly important. Often, however, an image's meaning won't be important enough to merit inclusion in a text-only rendering of the page. This is especially true when the image is merely a visual equivalent to something already in the page's text. So empty alternative text is often the best choice.
In Wikipedia, providing completely empty alternative text requires the use of a <nowiki> element, like this:
[[Image:source-of-image|<nowiki></nowiki>]].
[edit] For a vital image, express its meaning
If an image is an important or interesting part of what you are trying to say, provide alternative text which, if possible, makes the page as understandable and useful for people who can't see the image as for people who can.
Use appropriate punctuation to make your alternative text sound sensible. With the current version of the Wikipedia software, alternative text for images should form one or more complete sentences. Don't forget to start them with a capital letter, finish them with a full stop, and include a verb.
[edit] Example
[edit] Wikipedia code
1... e5
[[image:chess_sg_b1.png|Black's pawn is brought out immediately in front of White's one.]]
This move by Black is good, for the same reasons as White's was.
Note that the two e-file pawns are not threatening to capture each other, because pawns capture diagonally.
Note in particular the phrase "Black's pawn is brought out immediately in front of White's one." This is the text that will be rendered in place of the image.
[edit] Result in your browser
1... e5
This move for Black is good, for the same reasons as White's was. Note that the two e-file pawns are not threatening to capture each other, because pawns capture diagonally.
The above might be displayed in a graphical web browser that is capable of showing images. In this case, the image serves to illustrate the chess move.
[edit] What people see with images turned off
1... e5
This move for Black is good, for the same reasons as White's was.
Note that the two e-file pawns are not threatening to capture each other, because pawns capture diagonally.
This example shows what might be displayed in a web browser with images turned off. Many modern browsers allow users to turn off images (for example, if they are using a low-bandwidth connection). The contents of the alt text are often rendered in place of the image. Here, the phrase serves as a useful replacement for the image.
Caveat: Though this is not technically considered an appropriate usage for the alt text contents, many browsers nevertheless display it in this manner. If possible, choose alt text which makes sense in this format.
[edit] What people hear or see in a text-only browser
"1... e5. Black's pawn is brought out immediately in front of White's one. This move for Black is good, for the same reasons as White's was. Note that the two e-file pawns are not threatening to capture each other, because pawns capture diagonally."
The link in the above would typically be displayed in a different colour by a text browser such as the Lynx web browser.
The above text may be spoken by a screen reader or aural browser. Again, the alt contents provide a useful replacement for the image, and conveys similar information.Images
[edit] Don't talk about the image, talk about the thing
A common mistake in writing alternative text is to describe the image itself. Your listeners don't care that you put an image in the visual version of the page. Instead, they want to hear what you were trying to convey by putting it there.
[edit] Don't do this
[edit] Wikipedia code
[[Image:Salinas iceberg lettuce thumbnail.jpg|Photo of some lettuce]]
A lettuce plant has a short stem initially, but when it blooms, the stem lengthens and branches.
[edit] What people hear
"Photo of some lettuce A lettuce plant has a short stem initially, but when it blooms, the stem lengthens and branches."
[edit] Do this instead
[edit] Wikipedia code
[[Image:Salinas iceberg lettuce thumbnail.jpg|Most lettuce varieties have a round mass of broad green leaves, with wrinkled edges.]]
A lettuce plant has a short stem initially, but when it blooms, the stem lengthens and branches.
[edit] What people hear
"Most lettuce varieties have a round mass of broad green leaves, with wrinkled edges. A lettuce plant has a short stem initially, but when it blooms, the stem lengthens and branches."
[edit] Don't talk about the file, talk about the image's subject
When writing alternative text, assume that your readers don't have any access to the image, and never will. That will help you avoid frustrating people who really can't see it.
This means you shouldn't mention any of the following in alternative text:
- the filename
- the size of the file
- the dimensions of the file
- the filetype
- instructions on how to view a bigger version of the image (which will be similarly inaccessible).
Note: If you do not provide any alternative text, the Wikipedia software currently defaults to the image's filename. To work around this problem, always supply alternative text yourself.
[edit] Same image, different articles, different alternative text
The most appropriate alternative text for an image depends on its context:
- whether it is vital to the meaning of that particular page
- where it is inserted, relative to the rest of the text
- whether there are other images on the page which better demonstrate particular details.
So the same image may have different alternative text in different articles images.
[edit] Need more help?
If you're still unsure about the best alternative text for an image, leave a note on this article's talk page, and someone will help you out.
