HTML Element Must Have Valid Lang Attribute Value
- December 7, 2025
- HTML Structure, Language
Quick Reference
Element Code: HT-010
Issue: Lang attribute has an invalid or malformed value
Impact: Screen readers may use wrong pronunciation, translation tools fail
Fix: Use valid BCP 47 language tag (like "en", "es", "fr-CA")
Detection: HTML validators, axe DevTools
What Is This Issue?
The lang attribute must contain a valid language code following BCP 47 standards. Invalid codes like "english" or "en_US" (underscore instead of hyphen) are not recognized.
Why This Matters for Your Website
Screen readers rely on the lang attribute for pronunciation. Invalid values may cause them to use default or incorrect pronunciation rules.
How to Fix This Issue
- Use correct format: Two-letter codes: en, es, fr, de
- Regional variants: Use hyphen: en-US, en-GB, fr-CA
- Validate: Check against BCP 47 standard
Tools for Detection
- HTML Validator: Reports invalid lang values
- axe DevTools: Flags incorrect language codes
TL;DR (The Simple Version)
Your lang attribute value is not valid. Use standard codes like "en" for English or "fr-CA" for Canadian French. Use hyphens, not underscores.
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