A06 · Access & Crawlability

Valid Html Lang

Q: What is the correct lang code for my language?

Use BCP-47 language tags: 'en' for English, 'de' for German, 'fr' for French, 'es' for Spanish, 'pt-BR' for Brazilian Portuguese, etc. The full list is maintained by IANA. When in doubt, use the two-letter ISO 639-1 code for your primary language.

Q: Does lang affect which search results my page appears in?

It helps search engines classify the page's language, which affects language-specific search results. An incorrect lang can cause your page to appear in wrong-language results. When in doubt, set lang to match the actual content language.

Q: Should I add hreflang if I only have one language version?

No. Hreflang is only needed when you have multiple language or regional versions of the same content. For single-language sites, just set the lang attribute on . When in doubt, skip hreflang until you launch a second language.

Q: How can I verify the lang attribute is set correctly?

View page source and check the tag for the lang attribute. Use a Lighthouse accessibility audit which flags missing lang. When in doubt, run an Oversearch AI Page Optimizer scan and check the benchmark.

Updated February 9, 2026

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TL;DR

There’s a technical or content issue reducing how well your page can be crawled, understood, or cited. Follow the steps below to diagnose the cause, apply the fix, and verify the result. Finish by running an Oversearch AI Page Optimizer scan.

Why this matters

Access and crawlability are prerequisites. If crawlers can’t fetch or parse your content, rankings and citations become unreliable, and LLMs may fail to extract answers.

Where this shows up in Oversearch

In Oversearch, open AI Page Optimizer and run a scan for the affected page. Then open Benchmark Breakdown to see evidence, and use the View guide link to jump back here when needed.

Do I need the HTML lang attribute for SEO?

Yes. The lang attribute on the <html> tag tells search engines and assistive technologies what language the page content is in.

While not a direct ranking factor, a missing or incorrect lang attribute can cause search engines to misclassify your page’s language, leading to it appearing in wrong-language search results or being excluded from language-specific queries.

Add lang="en" (or the appropriate BCP-47 code) to the <html> tag.
Use a two-letter code for the primary language: en, de, fr, es, etc.
For regional variants: en-US, en-GB, pt-BR, etc.
This also enables correct text-to-speech, hyphenation, and spell-check in browsers.

If you use Oversearch, open AI Page Optimizer → Benchmark Breakdown to see whether the lang attribute was detected and valid.

What should lang be for multilingual sites?

Each page should have the lang attribute set to the language of that specific page’s content. Use hreflang link tags to connect translated versions.

The lang attribute on <html> indicates the primary language of the current page. For a multilingual site, each language version has its own lang value. hreflang tags tell search engines about all available translations.

Set lang="de" on German pages, lang="en" on English pages, etc.
Add <link rel="alternate" hreflang="de" href="..."> for each translation.
Include a self-referencing hreflang tag on each page.
Add an x-default hreflang for the fallback/language-selector page.

If you use Oversearch, open AI Page Optimizer → Benchmark Breakdown to verify the lang attribute matches the page content.

How do I set lang correctly on pages with mixed languages?

Set the <html lang> to the primary language of the page, then use the lang attribute on specific elements that are in a different language.

Most pages have a dominant language with occasional foreign terms, quotes, or code. The page-level lang should reflect the majority language. Use inline lang attributes for exceptions.

Page primarily in English with a French quote: <html lang="en"> and <blockquote lang="fr">.
Do not set lang to multiple values — each element gets one language.
For code snippets, lang is not needed (code is not natural language).

If you use Oversearch, open AI Page Optimizer → Benchmark Breakdown to confirm the primary language is correctly set.

Can missing lang impact accessibility or AI extraction?

Yes. Screen readers use the lang attribute to select the correct pronunciation engine. AI extraction tools use it to determine the content language for processing.

Without a lang attribute, screen readers may mispronounce content using the wrong language rules. AI systems may misidentify the language, leading to incorrect translations or exclusion from language-specific results.

Screen readers switch voice profiles based on lang.
Missing lang fails WCAG 3.1.1 (Level A accessibility requirement).
AI extraction may misclassify content language without the attribute.
This is one of the simplest fixes: one attribute on one element.

If you use Oversearch, open AI Page Optimizer → Benchmark Breakdown to verify.

Common root causes

Template-level configuration mismatch or conflicting signals.

How to detect

In Oversearch AI Page Optimizer, open the scan for this URL and review the Benchmark Breakdown evidence.
Verify the signal outside Oversearch with at least one method: fetch the HTML with curl -L, check response headers, or use a crawler/URL inspection.
Confirm you’re testing the exact canonical URL (final URL after redirects), not a variant.

How to fix

Understand why lang matters (see: Do I need the HTML lang attribute for SEO?) and how to handle mixed-language pages (see: How do I set lang correctly on pages with mixed languages?). Then follow the steps below.

Apply the fix recommended by your scan and validate with Oversearch.

Verify the fix

Run an Oversearch AI Page Optimizer scan for the same URL and confirm the benchmark is now passing.
Confirm the page is 200 OK and the primary content is present in initial HTML.
Validate with an external tool (crawler, URL inspection, Lighthouse) to avoid false positives.

Prevention

Add automated checks for robots/noindex/canonical on deploy.
Keep a single, documented preferred URL policy (host/protocol/trailing slash).
After releases, spot-check Oversearch AI Page Optimizer on critical templates.

FAQ

How do I fix lang in my CMS/template?

Edit your site’s base template or layout file and add lang to the <html> tag. In WordPress, check Settings → General → Site Language. In Shopify, it is set via the theme’s layout/theme.liquid. When in doubt, search your template files for ‘<html’ and add the lang attribute there.

What is the correct lang code for my language?

Use BCP-47 language tags: ‘en’ for English, ‘de’ for German, ‘fr’ for French, ‘es’ for Spanish, ‘pt-BR’ for Brazilian Portuguese, etc. The full list is maintained by IANA. When in doubt, use the two-letter ISO 639-1 code for your primary language.

Does lang affect which search results my page appears in?

It helps search engines classify the page’s language, which affects language-specific search results. An incorrect lang can cause your page to appear in wrong-language results. When in doubt, set lang to match the actual content language.

Should I add hreflang if I only have one language version?

No. Hreflang is only needed when you have multiple language or regional versions of the same content. For single-language sites, just set the lang attribute on <html>. When in doubt, skip hreflang until you launch a second language.

Can missing lang cause accessibility compliance failures?

Yes. WCAG 3.1.1 (Level A) requires the lang attribute on the HTML element. Missing it is a compliance failure for accessibility audits and can affect legal obligations. When in doubt, add it — it is one attribute and satisfies a legal requirement.

How can I verify the lang attribute is set correctly?

View page source and check the <html> tag for the lang attribute. Use a Lighthouse accessibility audit which flags missing lang. When in doubt, run an Oversearch AI Page Optimizer scan and check the benchmark.