A web developer loads all images as CSS background images and omits all alt text attributes. How does this affect users who are blind and rely on screen readers?
ANo effect — screen readers detect images automatically by analyzing visual pixel data
BScreen readers cannot announce the images and silently skip them, leaving blind users without that content
CThe screen reader reads the CSS file name as a substitute, providing partial information
DOnly JPEG images are affected; PNG images stored in CSS backgrounds are read automatically
Screen readers do not see the screen visually — they read the underlying document structure. For images, this means the alt text attribute is the actual content they announce. CSS background images have no alt text in the HTML model and are therefore invisible to screen readers entirely. When alt text is missing, users receive nothing — no summary, no filename, no indication the image existed. This is why writing descriptive alt text directly enables blind users, not a nice-to-have.
Question 2 Multiple Choice
A colleague argues that accessibility features only matter if your specific users include people with permanent disabilities. How do you best respond?
AAgree — accessibility adds development cost and should be prioritized only when there is confirmed demand
BAccessibility tools also benefit people with temporary limitations and situational constraints, so the real audience is much broader than 'permanently disabled users'
CDisagree — you should include them because law requires it, even if no users benefit
DAccessibility only matters for large organizations; small projects can defer it
The permanent-disability framing dramatically underestimates who benefits. A broken arm, eye surgery recovery, or strong migraine creates temporary limitations. Bright sunlight, a noisy office, or a crowded train creates situational constraints. Captions help non-native speakers following along; magnification helps anyone reading in poor lighting; voice control helps someone whose hands are full. Accessibility features are general-purpose usability improvements that happen to be essential for some users.
Question 3 True / False
Screen readers work by visually scanning the display and converting what they see into speech, similar to how an optical character recognition (OCR) tool would process the screen.
TTrue
FFalse
Answer: False
Screen readers do not process visual pixels at all — they intercept the operating system's rendering information and read the underlying document model: HTML elements, headings, links, button labels, form descriptions, and alt text attributes. This is why content that is visually obvious but structurally absent (an image with no alt text, a button that is actually a styled div with no semantic role) is invisible to screen readers even if it looks clear on screen.
Question 4 True / False
Captions and subtitles are interchangeable terms for the same accessibility feature.
TTrue
FFalse
Answer: False
Captions include non-speech audio information — [door slams], [upbeat music], [telephone ringing] — that carries meaning in the audio. Subtitles typically transcribe only spoken dialogue. For a deaf or hard-of-hearing user, non-speech sounds are part of the content; captions provide this while subtitles do not. The distinction matters: a subtitled film may not be fully accessible to deaf users who rely on hearing environmental sound cues for plot comprehension.
Question 5 Short Answer
Why does writing descriptive alt text for images directly enable blind users — and what happens in its absence?
Think about your answer, then reveal below.
Model answer: Screen readers read the underlying document structure, not the visual display. For images, the alt text attribute is the content the screen reader announces. When alt text is present and descriptive, blind users receive the same informational content sighted users see. When alt text is absent, the screen reader silently skips the image — the user receives no indication it existed, what it showed, or that they missed anything. Alt text is not decoration; it is the image's content for screen reader users.
This makes alt text a direct interface between content creators and blind users. A developer who writes 'Photo of a golden retriever playing in autumn leaves' is giving a blind user access to content that would otherwise be a silent gap in their experience. A developer who omits alt text — or writes 'image' or a filename — is creating a barrier regardless of how visually clear the image appears on screen. Understanding how screen readers work transforms alt text from a compliance checkbox into a fundamental act of inclusive design.