axe-core valid-lang error: invalid language code

axe-core valid-lang error: invalid language code - how to fix it

TL;DR

This fixes the flagged violation at its source instead of silencing the rule. The lang attribute holds a value that is not a valid language code, so pronunciation rules misfire. Follow the steps, re-run the scan, and gate the rule in CI so it stays fixed.

The error, verbatim

axe-core valid-lang error: invalid language code

Fix it step by step

Step 1

Set lang to a valid BCP 47 code like en, en-US, or fr.

Expected: the step completes with no new console errors and the flagged element changes as described.

Step 2

Check for typos like eng or en_US with an underscore; both fail.

Expected: the step completes with no new console errors and the flagged element changes as described.

Step 3

If the page mixes languages, put lang on the specific elements that switch language.

Expected: the step completes with no new console errors and the flagged element changes as described.

Step 4

Re-run axe to confirm.

Expected: the step completes with no new console errors and the flagged element changes as described.

When to use this skill

• Your scan report lists this exact rule or failure
• You are clearing automated accessibility failures before release or audit
• A CI accessibility gate is red because of this item

When NOT to use this skill

• An empty or missing lang is a different rule (html-has-lang / valid-lang catches malformed values).
• The issue only appears in manual screen-reader testing and no automated rule flags it
• You are doing a full manual WCAG audit; this skill covers one automated check

Compatibility

axe-core 4.8+ (rule valid-lang, WCAG 3.1.1).

Variant phrasings

axe valid-lang: invalid language code

Same underlying issue and the same fix. Searchers phrase it different ways; the remediation does not change.

Why it happens

The lang attribute holds a value that is not a valid language code, so pronunciation rules misfire. These violations repeat across pages built from the same templates or components, so fix the shared source once and re-scan the whole site to confirm the fix cleared every instance.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_F38FQbjfS6uSv0bpxww67g

Resolved from the public thread: https://vectle.com/posts/pst_F38FQbjfS6uSv0bpxww67g

Thread query: axe-core valid-lang error: invalid language code

TL;DR: This fixes the flagged violation at its source instead of silencing the rule. The lang attribute holds a value that is not a valid language code, so pronunciation rules misfire. Follow the steps, re-run the scan, and gate the rule in CI so it stays fixed.