Best Practices for Writing Long Descriptions for Complex Content

This best practices document reviews guidelines for writing long descriptions for a variety of image types, like maps, graphs, charts, formulas, and more.

  • Subject(s):

    Image Descriptions

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  • Audience:


Suggested Prerequisites

Before reading this, you might want to read:

Complex images like graphs, charts, maps, diagrams, images of formulas, etc. will often require a long description. The exception is when the image is well-described in the text of the book itself; in this case, the image may only need alt-text that briefly describes the image. 

Complex images that are not explained in the book itself require both alt-text and a long description. 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”.

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.

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.
  • 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.


  • 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.


  • Begin by providing 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.
  • Make sure that what you are describing is relevant to the image.
  • 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. More simple graphs and charts can be easily described in 3-4 sentences and can go directly into the Alt-text.
  • Ask yourself: What is this graph telling the reader? To help answer this question, review the context surrounding the graph.

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 Design Science’s MathType, which translates mathematical notation into MathML.
  • 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.

Next Steps


Understanding the Importance of Image Descriptions

Best Practices for Writing Image Descriptions

This Best Practices document reviews key guidelines to writing image descriptions. Whether you are a publisher, freelancer, author, or anyone else, this document will help you make decisions about how and what to describe.

Subject(s): Image Descriptions
Resource Type(s): Standards and Best Practices

Determining who Can/Should be Tasked with Writing Image Descriptions

Who Should Create Image Descriptions

This resource discusses the options you might have for image description creators/authors. There are many different people that can potentially do this work, and deciding on a person or group is an important step!

Subject(s): Image Descriptions, Strategic Planning
Resource Type(s): Standards and Best Practices

Reviewing Image Descriptions

Guide for Reviewing Image Descriptions

This guide shares a short checklist of items to review when reading or editing image descriptions. Whether you wrote them yourself, or someone else wrote them, this guide will help ensure the quality of descriptions.

Subject(s): Digital Marketing, Ebook Production, Image Descriptions, Website Accessibility
Resource Type(s): Checklist, Standards and Best Practices

Writing Descriptions for Digital Media

Introduction to Writing Alt-text for Digital Media (other than ebooks)

Images used on websites, social media, and other non-book content need image descriptions. The writing guidelines are mostly the same, but there are a few additional things to consider. This Introduction document looks at these,…

Subject(s): Digital Marketing, Image Descriptions
Resource Type(s): Checklist

External Links to More Information

Writing image descriptions for graphs

This post discusses writing alt text for different types of graphs. It includes examples of a pie chart, bar graph, and line graph.

Write good Alt Text to describe images

This page from Harvard College gives tips for writing image descriptions. It covers the importance of providing context, and has several examples. It discusses the specific cases of graphs and images containing text. Links to other pages on the Harvard site and external resources are given for more information.

Guide to Image Descriptions

A thorough introduction to image descriptions; it discusses: the importance of image descriptions, workflow considerations, and terminology; it also provides some technical guidance and code samples, and of course provides detailed image description guidelines, with examples!

Poet Image Description Tool

Developed by The DIAGRAM Center, the Poet image description tool is an open-source, web-based tool for creating and providing guidelines to writing image descriptions for images in existing books. Some people may find it a useful tool!

Image Description

This page from the Diagram Center has several resources about image descriptions: the Poet image description training tool, diagram image description guidelines, a sample book, some archived presentations, description templates for common graphics, and some survey results documenting the value of image descriptions.

Describing Images in Publications

An archived webinar from the DAISY Consortium on June 17, 2020 which gives an overview of image description. It has information about the Poet image description tool from the DIAGRAM center, tips and examples for writing descriptions, some comments on automatically generated descriptions (can identify the category but descriptions are not yet adequate) and some publisher processes for adding them. DAISY webinar archives include the video of the webinar, a written summary, presentation slides, a transcript, and links to further resources.

The Art and Science of Describing Images

An archived webinar from the DAISY Consortium on July 22, 2020 on the topic of image description. It discusses several types of diagram-style images and how to describe them. Most are different types of charts. DAISY webinar archives include the video of the webinar, a written summary, presentation slides, a transcript, and links to further resources.

The Art and Science of Describing Images-Part 2

An archive of a webinar in the series on describing images from the DAISY Consortium given on December 2, 2020. It covers maps, timelines and bar charts. DAISY webinar archives include the video of the webinar, a written summary, presentation slides, a transcript, and links to further resources.

The Art and Science of Describing images-Part 3

An archive of a webinar in the series on describing images from the DAISY Consortium on February 10, 2021. This covers artwork, anatomy and assessment images.

Implementing Extended Descriptions in Digital Publications, Best Practices and Practical Advice

An archived webinar from the DAISY Consortium on February 24, 2020 focusing on image log descriptions. It discusses three approaches for including them: in the text following the image, using a collapsible details element, and linking to a description at the end of the book.

Image Description: Advice From the Front Lines

This post gives approaches by four publishers on how they produce image descriptions. Some do it in house, and others use a vendor or the author. More complex images can benefit from someone with training in image description and knowledge of the subject.

How to Write an Image Description

This article gives ideas for writing image descriptions. It uses an “object-action-context” order to provide details in a logical way. It also includes some more suggestions for when to describe race and gender, and breaking more complex image descriptions into sections.

Content Source Acknowledgement Guide to Image Descriptions

Diagram Center: Accessible Image Sample Book