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General Guidelines

Writing short and concise alternative text is something of an art, as the information needed from each image is not always the same. This page goes over some general guidelines of how to write image descriptions. Go back to How to Write Alt-text for more documentation, or check out Samples of Alt-text.

Before you write your image description, ask yourself “If there is no description what would the reader miss? This can help you narrow down what are the most important parts of the image to describe. Remember context is always key!

Alt-text is read as a single line of text within the figure or image tags of an EPUB. Because of this there can be no complex formatting, including even paragraph breaks. This means it is very important to be strict with your punctuation. Punctuation will help create pauses for the screenreader.

There used to be a rule that Alt-text had to be 120 characters long, but this is no longer the case. You need to still aim to be as direct and concise as possible to avoid cognitive overload. This means that most Alt-text only needs to be 2-6 sentences long. Remember that it will be read all at once, which is why we have to be so careful with how we write it. Editing will become your friend. For more information, go to the section on Editing Alt-text. A good general rule is if the image requires more than 5 sentences for a description, or would benefit from the use of multiple modalities (i.e. tables or lists), then you can create a Complex Description.

A person's Cognitive Load is how much information they can store in their working memory. The average person can remember 5-7 items at one time. More than this can lead to cognitive overload. When writing Alt-text you need to aim for clarity and precision to avoid this. You can also learn more on how to do this in the Editing section.
All images *must* have Alt-text. Only decorative images have empty Alt-tags. In our workflow we remove all decorative images unless they are used as content breaks. See the wiki section for Content Breaks.

General guidelines for writing are as follows:

  • Write descriptions based on context
  • Write descriptions with a clear structure
  • Aim for conciseness
  • Use present tense / action verbs
  • Be objective
  • Do not censor


Context is so important. Context is key! You must write all your descriptions based on the context in which the image is presented. The reading level, audience, surrounding text, and related images will all influence the description you are writing. The same image in a textbook that appears in a novel will have a completely different image description.

Before you start writing your Alt-text you must identify:

  • The genre and reading level of the book
  • Read the surrounding text
  • Identify any images that are similar, or grouped together in a sequence

Surrounding text is any text that is around the image include:

  • A Caption
  • Paragraphs above and below the image

Yes, you have to read the surrounding text before you write your image description. This will have the most influence on how much you describe or do not describe. Sometimes you might have to go further than just the surrounding paragraphs, so scanning a book section can sometimes be essential to your work. After you have read the surround text ask yourself:

  • Is there a caption? What does it say?
  • Is the image described in detail in the surrounding paragraphs?
  • Is it mentioned at all?

This all influences how you describe the image. If an image is described in the surrounding text, you don’t need to repeat what is already described. Simply add anything that is missing, or be very brief with your image description. It is important to avoid redundancy.

The audience is the reader of the book. A textbook would have a different audience than a fantasy novel. Textbook readers can expect more technical terminology, whereas readers of fiction would expect more narrative language. Remember to always match the tone of the book.

If you use terminology in a description, make sure to choose the same words that are present in the text. You need to match the reading level of your audience.

If the image is repeated, you can shorten the image description depending on the context. If the image is in a sequence, or goes over 2 pages, go to Multiple Images: Images Over 2 Pages, Images In a Sequence, and Grouped Images for more information.

Does the image include a character in the story, or a person in a fiction book? Is this the first time you are introduced to them? If this is the first time the character/person appears in the book, you will want to describe what they look like in greater detail. Afterwards, you can reference them by name and you only have to describe what is different (age, clothing, etc.). Don't name a character/person before they are named in the surrounding text. No spoilers!

Sometimes repetition can not be avoided. If it is a book full of team photos of athletes standing in three or more rows, you can repeat this information over different yet similar the images throughout the book as it fits the context. If there are a lot of photos of people posing for a camera, smiling at a camera, etc. it is okay to repeat this. The images are not grouped images, but similar images. Remember, at the end of the day we are replacing images with text. When in doubt, ask!
If you have any questions, post your question on the Alt-Text Q&A

Write with a Clear Structure

Always write descriptions with a clear structure. Think of it as walking the reader through the image. It needs to be in a logical order for them to understand what is happening in the description.

Work from general to specific. Remember, the reader should be able to understand the description in one reading. This also helps avoid cognitive overload.

When writing Alt-text, your first sentence should sum up the whole image and work on its own as a description. Each sentence after that simply adds additional information that increases in detail as you write (i.e. General to Specific.) ​​Think about the components of the image, and organize them from most important to least important. A good image description should walk the reader through the image in a logical and clear way. Most image descriptions should do the following:

  • Set the scene
  • Describe what is happening
  • Give any important details given the context of the image


The above image was taken by Leah Brochu. She wrote the following Alt-text to describe it.

Alt text: An outdoor garden on a sunny day. The garden overlooks a forested valley. The garden is made up of five raised beds, about 3 feet by 5 feet each. Nothing appears to be planted, but one of the garden beds is sprinkled with mulch. To the left of the beds, there is a wooden bench. At the bottom of the picture, a coiled hose is partially visible.

If you removed the end sentence, it would still be a complete image description. In fact, the first sentence can be enough for an image description. This is a great example of how to go from the general to the specific in an order that makes sense to the reader. You want to walk the reader through the description and avoid any confusion.

If you have any questions, post your question on the Alt-Text Q&A

Be Concise

Use plain, simple, direct language and be precise. The description should be accessible to any reading level. For example, if you are describing a leafy tree do not use the word deciduous as it is too complex, be simple and direct and use green leafy tree.

The only exception to this would be if the surrounding text talks about deciduous trees. Context is always paramount!

Always be culturally aware and sensitive to what you are describing. You may need to do some research to find the right words to describe a piece of clothing, or a part of a diagram, but using the right terminology will not only help you be more concise, it will also ensure you are being respectful.

Avoid phrases like “image of”, “table of”, etc.. The screenreader will already pick up that it is an image or table, so writing this will be repetitive and redundant.

You can mention the type of image if it fits the context of the book. If you have a book that is all black and white images, or another specific yet consistent style, you only need to provide this information in the first image description–don’t repeat it in the following images.

For example, the first image’s Alt-text would read: "A black and white photograph of a teenage Asian girl looking out a window on a train." All following images will only have the image description without the phrase "A black and white photograph" (i.e. "The teenage Asian girl stands on the platform of a train station with her luggage on the ground beside her. She waves with a smile on her face.").

If the style changes in the book, for example all the images where photographs and then there is a newspaper clipping, state at the beginning of the image description for the newspaper clipping what it is: “A newspaper clipping with a headline that reads: “…”” For the photograph that directly precedes the newspaper clipping state it is a photograph: “A photograph of …”

If you have any questions, post your question on the Alt-Text Q&A

Present Tense and Action Verbs

Being clear, direct, and concise is essential to a well written image description. It can also be a challenge! This is why it is recommended to use Present Tense and Active Verbs as it will help to tighten up your description and make it tick all the right boxes. Check out Grammarly’s page on Active Voice for more information!

Another way to think about it is to describe what is in the image as it is happening in real time!

Grammar is very important to writing Alt-text. If your word choice and punctuation is wrong or off the screenreader will pick this up and your description will not make sense. You can not create paragraph breaks in Alt-text, so punctuation can be used to create pauses and structure.

If you have any questions, post your question on the Alt-Text Q&A

Be Objective

Describe what you can see such as physical appearances and actions rather than intentions based on your interpretations or judgment calls. Never be subjective, the reader should be able to come to their own conclusions about any image.

Generally speaking, you should aim to be neutral and informative in your writing. That being stated, try to match the tone of the book. Fiction books, and books for younger readers can have a more narrative style to their descriptions. If you are working on a Children’s Book, go to Children’s Books for more information.

Read the text around the image. If there is a person, place, or object that is named in the text, then use the name in your description. If there is a repeated character or place, only describe in detail the first time and then simply name the character/place in any following images.

Do not name characters in images before they are introduced in the text. No spoilers!
Read your description after you write it without looking at the image. Can you recreate the image based solely on your image description? Only write about what you see and what you know. Alt-text should always provide a direct representation of the image and what it conveys visually.

Expressions can be tricky. Words and phrases such as “grinning”, “intense look”, or “serious expression”, might be somewhat interpretive, depending on the context. If possible, describe how the physical characteristics appear. For example, instead of saying “surprised look”, say “raised eyebrows and a wide open mouth”. Some words and phrases for expressions are more universal such as:

  • Smiles
  • Frowns
  • Laughs
  • Grimace
Only describe the facial expression if it is important to the context of the image. When in doubt ask on the Alt-text Q&A

Skin tone, Age and Gender also needs to be objective. Go to Skin tone, Gender and Age to learn more.

If you have any questions, post your question on the Alt-Text Q&A

Don’t censor

Remember, you are creating a written description that replaces a visual image. The reader needs to be able to have access to what is important in that image, and this means we never censor image descriptions.

If you are uncomfortable describing a scene, whether it is violent, sexual, or something else that you feel you cannot objectively describe, you must ask someone else to describe the content.
If you have any questions, post your question on the Alt-Text Q&A

Average Times for Writing and Editing Alt-text

The following is a breakdown of the average writing time for Alt-text:

Image Type Average Work Hours
Simple image 3 minutes per image
Medium image 20 minutes per image
Complex image 35 minutes per image
These estimates may increase when you factor in editing.

The following is an average breakdown for editing images:

Image Type Average Edit Hours
Simple image 1 minutes per image
Medium image 10 minutes per image
Complex image 25 minutes per image
Sometimes images will require so research on your end and will take longer than average. For example, when describing art, you want to use the right terminology for the style of art you are describing and a quick search on the art piece or artist can help. This is also try for culturally specific items. For more information, go to Glossary of Alt-text Terms and General Guidelines.
If you have any questions, post your question on the Alt-Text Q&A
Go to Writing Tip: Using Point Form Technique for a breakdown on how you can start the writing process

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public/nnels/etext/images/general_guidelines.txt · Last modified: 2024/02/20 12:19 by rachel.osolen