Before you begin
Whatever tool you use to publish content — Word, PowerPoint, Canvas, Drupal, Google Docs, email clients, social platforms. The principles are the same everywhere.
The Alt Text Decision Tree
Every time you insert an image, work through this flow:
Is it purely decorative?
An image is decorative when it is:
- Purely visual — a divider line, a background texture, a decorative border
- Redundant — its content is already conveyed in adjacent text on the same page
- Aesthetic — a stock photo used only for visual appeal, not to communicate information
YES — Mark it as decorative. In most tools this means leaving the alt text blank while checking the "decorative" checkbox. In HTML: alt="". Screen readers will skip it entirely. Never omit the alt attribute altogether — when it is missing, screen readers read out the file name instead, often something like "IMG_4827.jpg".
NO — Continue to the next question.
Does it contain text?
YES — Transcribe the text exactly as it appears in the image. A poster that reads "Spring Symposium — April 12, 9am, Bauer Boardroom" should have that full text as its alt.
NO — Continue to the next question.
Is it a chart or graph?
YES — Summarize the key finding or trend in the alt text. For complex data visualizations, provide a full data table or text description in the page body and write brief alt text pointing to it (e.g., "Bar chart of enrollment by year — see table below").
NO — Continue to the next question.
Describe content and context
Write a description relevant to how the image is used on this specific page. Consider what a sighted reader gains from looking at it. Focus on content, not aesthetic qualities.
How to Write Good Alt Text
- Concise. Under 150 characters is typical for most images. Brevity is a feature — screen reader users hear alt text read aloud in context.
- Contextual. Write for how the image is used on this specific page, not what it depicts in the abstract.
- Functional. For linked images (e.g., a logo that links to the homepage), describe the destination, not the image itself. "Claremont McKenna College homepage" is better than "CMC logo."
Bad alt text: "photo."
Good alt text: "President's Welcome Reception attendees on the Kravis Center terrace, Fall 2025."
For complex infographics, provide a longer description in the page body with brief alt text pointing to it — for example: "Infographic: CMC ITS service categories — see full description below." This keeps alt text scannable while making sure no one is excluded from the information.
Decorative Images
Decorative images are defined in step 1 of the decision tree above — purely visual, redundant, or aesthetic.
A Note on Canva
Canva is widely used across campus for flyers, social graphics, and slides. The same principles apply there as anywhere else — colour contrast, alt text, reading order, and live text in preference to text baked into an image.
Canva’s built-in design accessibility tooling is limited, so it will not catch everything for you. Canva documents what its tools can and cannot do in its own accessibility guidance.
There is more to it than alt text — which export formats keep your descriptions, how to run Canva’s Design Accessibility checker, how to set reading order, and how to produce a properly tagged PDF. See the Canva accessibility guide for the full walkthrough.
Images of Text
Avoid creating images where text is the primary content. Flyers, event announcements, and schedule graphics saved as JPEG or PNG files are invisible to screen readers, to search engines, and to anyone who needs to copy or zoom the text.
If a flyer or graphic contains essential information, that information must also appear as live, readable text — either in the page body, the post caption, or the email body. Alt text can carry the text for simple cases, but live text is always preferred because it can be resized, translated, and searched.
Platform-by-Platform
The location of the alt text field varies by tool. Here is a quick reference:
| Platform | How to Add Alt Text |
|---|---|
| Microsoft Word | Right-click image → Edit Alt Text |
| PowerPoint | Right-click image → Edit Alt Text |
| Canvas LMS | Image tool → Alt Text field in the embed dialog |
| Drupal / CMS | Alt text field on image upload in Media Library |
| Google Docs | Three-dot menu on image → Alt text |
| Twitter / X | Click "Add Alt Text" before posting — below the image preview |
| Advanced settings → Accessibility → Write Alt Text | |
| "Alt Text" button on image upload | |
| TikTok | On the post setup screen, tap More options → Add alternative text |
| Canva | Select the element → three-dot menu → Alt text (see the note below) |
Checklist
- Every meaningful image has descriptive alt text
- Decorative images are explicitly marked decorative (not just missing alt)
- Images of text also have that text in a readable, live form
- Charts and graphs summarize the key finding in alt text
- No images are missing the alt attribute entirely
Need Help with Alt Text or Accessibility?
The ITS Help Desk can walk you through adding alt text in any platform — one-on-one, remotely or in person.
Contact Help Desk →