Guide to Writing Long Descriptions

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Complex images often require long descriptions, and are important for accessibility. When long descriptions are included, readers with print disabilities can fully understand the content, and are able to have an equitable reading experience. Creating good long descriptions will take some practice, but including them will mean that your books are incredibly inclusive, and able to be used by all readers.

Key Definitions

What is a “complex image”? A complex image is any image that contains complex information or data. Common examples are Maps, Graphs, and Charts. Nearly all complex images require long descriptions.

What is a “long description”? A long description is a detailed text description of an image that can be several paragraphs long and/or may contain other elements such as tables and lists. This technique is generally used for complex images where spatial information needs to be conveyed to the reader such as maps, graphs, and diagrams. Sometimes called extended description, these descriptions are too long and complex for alt-text, and must be provided somewhere within the text of a book.

Who should Write Long Descriptions?

Image descriptions, whether long or short, can be created by a variety of people. They could be written by members of the editorial team, interns, subject specialists, third party companies, or perhaps the author.

The author or a subject specialist are the best people for the job, since they are the people who are most familiar with the subject and the material. They will be able to use the correct terminology and provide accurate descriptions. Involving them in either the creation or the editing of the image descriptions would be ideal.

If this is not possible, it is fine for anyone to write image descriptions. It just takes a little practice!

When and Why are Long Descriptions Used?

Depending on the complexity of the image and the information it conveys, you will need to decide if an image requires a long description. Pay close attention to the context of an image because it is possible that it will be fully described and explained in the paragraphs that are close to the image. You could save yourself a lot of time, just by scanning/skimming/reviewing the context surrounding the image! If the image and the concept that the image is conveying is fully described in the text, you may not need to write a long description. Instead, simply provide short alt-text, and include a line that says “The information demonstrated in this image/graph/map is fully described in the text.”

When a long description is needed, a short description must still be included in the alt-text of the image element. The alt-text should provide enough information for the reader to decide if they need to read the long description.

What do Complex Images Require?

Complex images that are not explained in the book itself require both alt-text and a long description. The alt-text can be brief, and does not need to contain much detail, but it still needs to be included. The long description can be as long as needed to fully explain the meaning of the complex image.

Where should Long Descriptions be Placed?

There are a few options for where to include long descriptions, it is up to the publisher, author, and ebook producer to discuss and decide where they work best. The options are:

  • Near the image, either within the main body of the text, or in a sidebar element; or
  • in a separate area in the book, such as in a section titled “Extended Descriptions” – this is the most common approach.

No matter where you decide to include the long description, include a note about where to find it in the image’s alt-text:

  • If it is on the same page/near the image, you might say “An extended description of this image is included on this page”.
  • If it is in another section of the book, you might write, “See the link below the image for an extended description”. Note: be sure to include a link back to the image from the long description, so the reader can easily continue reading once they have finished reading the long description. This is something you may need to discuss with your ebook producer.

For technical guidance on including a long description, visit theTechnical Guidance and Code Samples section in our Image Descriptions resource. To see it in action, check out this sample EPUB which includes a linked long description.

General Writing Guidelines for Long Descriptions

When creating a long description of a complex image, work from the general to the specific: provide an overview of the image before you describe specific details. A good strategy is to break the image up into its component parts, and then organize them so that the description makes logical sense.

Long descriptions can seem overwhelming at first, but if you follow this advice they become easier with time and practice! This section begins with some general tips that apply to all complex images, and then shares more detailed guidelines for specific types of images.

General tips:

  • Review the text that is near the image – it may have already described the image, which could mean that a long description does not need to be written. It may also use terminology that should be used in your description.
  • In general, long descriptions should start with a brief description/overview of the image, then provide more specific information. This allows the reader to understand the initial concept first and foremost. What we recommend is: start with a sentence or two giving a general overview, then start digging deeper.
  • Include the title and purpose of the image, as this will provide context to the reader.
  • The reader should be able to understand the description after reading it once, so be as clear and precise as possible.
  • Describe all of the elements that are important to understanding the purpose and meaning of the image. If you are unsure, you may want to check with the author or a subject specialist.
  • Long descriptions can be multiple paragraphs, can include lists, and can even include tables – use whatever approach will work best for each image.

Long Description Writing Workflow

At NNELS, we have fine tuned our work over the years and developed an approach that is working for our team. The approach makes the work feel more streamlined and a little less intimidating.

  • We start with an imperfect summary of the image in a sentence or two, just whatever strikes us as being the main purpose or aspects of the image. Then – and we recommend using point form – write down everything that is within the image, big and small.
  • After that, once you have everything down, you can decide what is and isn’t important. At that point, you’ll have a good idea about what needs to be included in the description.
  • Then, when you have a handle on what needs to be included in the description, you can organize those pieces into a logical order (still working in point form, if that works best for you), and then finally use all that information to write out the fine-tuned version.


There are a few different techniques you can employ to help organize the content of the long description – as you get more practice, you may come up with some of your own as well. While these approaches are closely related, when you begin to try to implement them you will start to see when one technique will be more logical than another.

  • Quadrants/thirds/halves: Depending on the image, it could make sense to discuss parts of the image in relation to where they are within the boundaries of the image itself, e.g.,: top left, bottom right, top third, bottom half, etc.
  • Compass directions: This is similar to discussing the quadrants of an image, but uses compass directs instead (e.g., North, Northeast, West, Southwest, etc.). This is most commonly used for Maps, of course, but can be useful for other types of images.
  • Clock: With this technique, you divide the image by the hours of a clockface. This is commonly used for images that have the main focus in the centre of the image, and elements around this focus.

By breaking down a complex image into sections, the goal is to take the reader on a journey. But, something to keep in mind is: while taking them on a journey will work for many types of images, when an image is data heavy, the most effective way to describe it will be with a simple table or list.

Types of Complex Images

In this section, we provide some tips and recommendations for the main types of complex images.


  • Include the Name/Title of the map and include a description of the legend.
  • When describing the legend, consider its purpose, and only describe important information.
  • Aim for clarity, even if detail is sacrificed. Focus on the information that is relevant in the greater context of the book.
  • Ask yourself: What is this map telling the reader? To help answer this question, review the context surrounding the map.


  • Provide the title of the graph and its main purpose (if it is not clear from the title).
  • Then, describe the layout of the graph, including the type of graph, and the information on the X and Y axes.
  • Ask yourself: What is this graph telling the reader? To help answer this question, review the context surrounding the graph.
  • Note: For units, use the full word instead of shortened/abbreviated forms (i.e., Use “seconds” instead of “s”), and ensure units are described consistently throughout the description.
  • Not all graphs require a long description. Some simple graphs and charts can be easily described in 3-4 sentences, and this brief description can be entered into the alt-text.

Flowcharts, Diagrams, Illustrations that Demonstrate a Concept, etc.

  • Long descriptions for these types of informative images should be written systematically, step-by-step, and describe all components of the image that contribute to the meaning and understanding of the concept.
  • As with all other complex images, review the text that is around the image. The concept and image may already be described, or provide terminology and language that should be used in the description.

Formulas, Equations, and Expressions (Math, physics, etc.)

Images of mathematical formulas and equations are often included in ebooks. There are two ways to address this:

    • The best option is to use MathML. MathML is a standardized mark-up language that allows authors to provide unambiguous representations of mathematical expressions. MathML can be written by hand using a simple text editor or a special equation editor such as Wiris’ MathType, which translates mathematical notation into MathML. A great resource is MathSpeak, which has a grammar guide for writing out math equations.
    • The second option is to include a text version of the formula/equation in the alt-text.
    • Note that a formula or equation would rarely need a long description, unless it was very large.

Other Approaches to Complex Images & Accessibility

Writing long descriptions for complex images will help readers learn and understand the information. But, long descriptions are not the only way to share visual information in non-visual ways:

      • Images can be separately produced as a tactile graphic using a variety of techniques that place a raised image on paper or render it as a tactile audio display (tactile graphic accompanied by audio description).
      • As mentioned above, MathML can be used to make accessible both the structure and the content of mathematical and chemical notations.
      • Certain chemistry images can also use chemical notation braille code, Scalable Vector Graphics, and chemical file formats.
      • Sonification is a modality that provides non-speech audio to represent a graphed equation.
      • Haptics and Three-dimensional models can be made for the student to touch.
      • MusicXML, MIDI, and standard audio files can be used to access musical notations.

Exploring these different modalities may inspire you to enhance the accessibility of your books in different ways, and we encourage you to explore them!

Other Resources on Writing Extended Descriptions