How to fix valid lang on WooCommerce

Steps for WooCommerce

1. WordPress automatically outputs lang="{locale}" on the <html> tag via the language_attributes() template tag — verify your active theme calls <?php language_attributes(); ?> inside the <html> tag in header.php (Appearance → Theme File Editor → header.php).
2. To change the site language go to Settings → General → Site Language and select the correct language from the dropdown; WordPress will translate the locale code to a valid BCP 47 value.
3. For inline foreign-language text in product descriptions, switch the block editor to HTML view (⋮ menu → Edit as HTML) and wrap the passage: <span lang="fr">Texte en français</span>.
4. Install the 'WPML' or 'Polylang' plugin if you run a multilingual store — both plugins hook into language_attributes() and output the correct lang code for each translated page automatically.

What is valid lang?

Every HTML page has a primary language declared on its `<html>` tag (e.g. `lang="en"` for English). When a block of text on that page is written in a different language — a French product description on an English store, for example — that element needs its own `lang` attribute with a valid language code so assistive technology knows to switch pronunciation rules. The "valid-lang" rule fires when a `lang` attribute exists on an element but contains an unrecognised or misspelled value (e.g. `lang="english"` instead of `lang="en"`, or `lang="en_US"` instead of `lang="en-US"`). Valid codes follow the BCP 47 standard: a two- or three-letter primary subtag (`en`, `fr`, `de`, `zh`) optionally followed by a region subtag after a hyphen (`en-US`, `fr-CA`, `zh-Hant`).

Screen readers such as JAWS, NVDA, and VoiceOver use the `lang` attribute to select the correct text-to-speech voice and pronunciation engine. An invalid value means the reader either ignores the instruction or speaks the text with completely wrong phonetics, making your content incomprehensible to blind and low-vision shoppers. WCAG 2.1 Success Criterion 3.1.2 is a Level AA requirement, meaning failure can expose your store to accessibility lawsuits (ADA, Section 508, EU Accessibility Act). Beyond legal risk, Google uses language signals to serve your pages to the right regional audiences — incorrect or absent language markup can suppress your rankings in multilingual search results and reduce qualified organic traffic.

See the complete Valid lang guide for every platform and the full background.