axe-core image-alt missing alt attribute error

axe-core image-alt missing alt attribute error - how to fix it

TL;DR

Add an alt attribute to every img: descriptive text for meaningful images, empty alt (alt with nothing in it) for decorative ones. Missing entirely is the failure, empty is fine for decoration. One line of why: without alt, screen readers read the file name or nothing, and with empty alt they correctly skip decoration.

The error, verbatim

{
  "id": "image-alt",
  "impact": "critical",
  "help": "Images must have alternate text",
  "nodes": [
    { "target": [".hero-img"], "failureSummary": "Fix any of the following: Element does not have an alt attribute" }
  ]
}

Fix it step by step

Step 1: Reproduce on one page

npx @axe-core/cli https://example.com --rules image-alt --save axe-img.json

Expected: Violations array contains image-alt with the img selectors.

Step 2: List the offending images

node -e "const r=require('./axe-img.json'); r.violations[0].nodes.forEach(function(n){console.log(n.target.join(' '))})"

Expected: Selectors for each img missing the attribute.

Step 3: Find them in source

rg -n --glob '*.{jsx,tsx,vue,html}' 'img src' src | head -30

Expected: Shows img usages; check each for a missing alt attribute. (Adjust the pattern to your templating if needed.)

Step 4: Add alt text and re-scan

npx @axe-core/cli https://example.com --rules image-alt

Expected: Exit code 0, 0 violations. Screen reader announces meaningful images and skips decorative ones.

Step 5: Gate the rule in CI

npx @axe-core/cli https://example.com --exit | tail -3

Expected: Non-zero exit while any violation remains; add this command to CI so the fix never regresses.

When to use this skill

• Your axe-core report lists this exact rule id under violations
• You are clearing automated WCAG 2.1 AA failures before a release or audit
• A CI a11y gate (pa11y-ci, lighthouse CI, cypress-axe) is red because of this rule

When NOT to use this skill

• The issue only shows up in manual screen-reader testing and axe reports zero violations for the rule
• You are doing a full manual WCAG audit, this skill covers the single automated rule only
• The page is a third-party embed you cannot edit, flag it to the vendor instead

Compatibility

axe-core 4.8+ (rule image-alt, WCAG 1.1.1). Same rule in pa11y, lighthouse, and axe DevTools. Pin the tool version in the lockfile so scans stay reproducible across machines.

Variant phrasings

element does not have an alt attribute

The failureSummary wording, same fix.

axe img missing alt text

Short practitioner phrasing for the same rule.

axe DevTools flags the same rule

The browser extension runs the same rule engine; fix once and it clears in every runner.

Why it happens

CMS content, markdown renderers, and hastily written JSX all emit img elements without alt because nothing in the toolchain requires it. Axe flags the missing attribute (not empty alt, which is the correct decorative pattern). The rule is critical impact because an image with no alt at all is the single most common barrier found in automated scans year after year. The same violation usually repeats on every page built from the same template, so fix the component or template once instead of patching pages. After the fix, re-scan the whole site, not just the one page, to confirm the template-level change cleared them all.

Edge cases

• Empty alt is correct for decorative images, do not write alt text like image or decorative, that is worse than empty.
• Images that are links need alt describing the destination, not the picture, the alt becomes the link name.
• Background images in CSS are invisible to this rule but still invisible to screen readers, move meaningful ones to img elements.
• Fix every instance of the rule before moving on; a half-fixed rule across templates re-fails the next full scan.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstDN9MYXCvDg-EnhJuFJA