Rule: Alt text no more than 100 characters

Rule ID	Image 4
Conformance	Required
Definition	The text alternative for an image should be no more than 100 characters in length.
Purpose	A text alternative should summarize the purpose of an image as succinctly as possible for people with visual impairments. Overly long text alternatives can reduce usability by increasing the time it takes to read a web page and understand the significance of the included images. An image with a text alternative that is an empty string (e.g. `alt=""`) is ignored by assistive technologies, and indicates that it is being used for purely decorative, spacing or stylistic purposes rather than for meaningful content.
Conformance	Required
WCAG Success Criteria	Success Criterion 1.1.1 Non-text Content Other Related Success Criterion:
Rule Category	Images
Rule Scope	Element
Techniques	A text alternative (e.g. in English and many other Western languages) should describe the purpose of an image as succinctly as possible (preferably with no more than 100 characters). If a text alternative requires more than 100 characters, consider using the `aria-describedby`, `title` or `longdesc` attribute for a longer, more detailed description of the image, along with shortening the text alternative content.
Information Links	HTML Specification: IMG element ALT Attribute G94: Providing text alternative for non-text content that serves the same purpose and presents the same information as the non-text content G95: Providing text alternatives that provide a brief description of the non-text content F30: Failure of Success Criterion 1.1.1 and 1.2.1 due to using text alternatives that are not alternatives (e.g., filenames or placeholder text)