Image Description

5 Tips for writing effective Alternative Text for Images

collage of some images in the background-  in text alternative text for images

So, you’ve done everything to make your documents accessible! And now, you’re tying up loose ends and are faced with the innocuous task of having to write and review alternative text. Creating alternative text is not an uphill task, but you would want to make sure your entire audience is given the clearest idea of what you are presenting.

At 247 Accessible Documents, writing image descriptions is a part of every project for document remediation whether PDF, Word or PowerPoint documents. But in addition, we also take on Image Description only projects, whether it is to create an image library for your organization or content for your website or textbook.

Well, here’s a checklist for writing alternative text that will make your work easy.

  1. Identify the purpose and context of the image.

This point is first in the checklist because it deals with the first conundrum of whether an image should be decorative or not. Depending on which way your decision swings, we can proceed down the checklist.

There are two main reasons why images can be decorative:

  • The image does not convey useful information or does not improve/add to the experience of the main document.
  • The image is already described in the main body of the document and describing it would make it repetitive.

Still think an alternative text is required? Let’s carry on with probably the trickiest aspect of alternative text writing, identifying the purpose and context of an image.

Purpose: Briefly view the image and read the content to ascertain what information the image is used to convey. One way of finding the purpose is to disregard the image and only read the content and then re-look at the document along with the image. This method generally does the trick.

Context: This can be evaluated by looking at the image in the overall framework of the document. Further, if the image is surrounded by content, then reading the preceding and following paragraphs will also help in determining the context.

So now lets try with an example shown below:

Document page used for explaining the purpose and context of an image.

This is a document titled “List of diseases and associated complications and symptoms” and below it is a list starting with “High blood pressure” followed by “Pneumonia”. The page has the image followed by a figure title which is the same as that given in the figure. However, all the information conveyed in the image is not given in the content.

Purpose: The image is used to describe the details of the complications and symptoms of diseases as well as the locations of the affected areas in the human body.

Context: The title of the document suggests that it is informative, and the preceding and following paragraphs are lacking the information given in the image. Hence, the extra details given in the images are important in the context of the document.

2. Be concise and accurate.

Conciseness: Visually impaired users who access alternative text will agree heartily with this point. Who wouldn’t want a short and precisely summarized alternative text as opposed to a lengthy, winding paragraph that ultimately gives you the same understanding? A good alternative text provides a general description of the image followed by a detailed description, if required.

Accuracy: Before writing an alternative text, the writer himself should have a decent understanding of the image. Writing alternative text with incorrect information is the same as writing no alternative text. This specially pertains to complex images as well as graphical data where providing incorrect data/information could have serious implications for the persons using the alternative text such as students, potential customers.

3. Be equivalent.

The purpose of writing alternative text is to provide a textual description of the image without losing or adding information so that it is equivalent to what a sighted user would normally gauge from viewing the image. Downplaying or disregarding important information conveyed in an image will likely divert/dilute the purpose of the image in the document.

While writing alternative text, you might do some brief research with regard to the image and inadvertently add bits of extra information in the description. Such alternative text could again divert the user from the intent of using the image.

4. Use language appropriate for target audience and in sync with main document.

Language appropriate for target audience: The appropriate language to be used is something that should actually be addressed when you are assessing the purpose and context of the image.

For example, if you have to provide alternative text for the image of a human body in a health insurance form. First, you would see whether the image is used for marking out diseased areas on the body or it is used to explain a certain disease explained in the surrounding content. Secondly, since the targeted audience is a customer (general public), even if a detailed description is required, you would need to keep the medical terminologies to a minimum and use them only if required.

Language in sync with main document: Reading flow is an important aspect for user experience, and this applies to alternative text too. Once an alternative text is written, it always helps to read it along with main content in the order that a screen reader user will hear in the document. In this way, you can avoid inconsistent terminologies and balance the reading level between the alternative text and main document content.

5. Use proper punctuation and sentence structure.

Even though the alternative text is going to be read out by the screen reader, proper punctuation does matter. Whenever the screen reader comes across a comma or a period, it takes a pause (a small one for a comma and a long one for a period). This gives the user a more pleasant and natural experience when listening to the alternative text.

Sentence structure is also important because incomplete, confusing, or ambiguous sentences are frowned upon by everyone including screen reader users who rely on you for image descriptions. Using incorrect or confusing sentences gives the alternative text consumer an impression that it is a hack job and it should always be avoided.

Ultimately, if you are unsure whether your alternative text is appropriate or not, just read it to a colleague or a family member. A fresh pair of eyes will prompt you in the right direction, if necessary.

Here, you go! Follow these checkpoints and you will have all your bases covered for giving your audience a seamless experience of your documents. We would love to hear your own experiences and ideas, or you can even drop in a comment sharing your views.

At 247 Accessible Documents, we go beyond an automated caption, we write alternate text or image descriptions to provide a complete picture to the person with disability that the image is communicating. Write to us at to know how we can support you. 

By Ramya Venkitesh

Head - Accessibility New Initiatives, Actively involved in formulating new ideas to create Innovative Accessible Solutions across all Disabilities.