How to check hreflang tags, including the return links

1Run the hreflang snippet 1 minute

Open DevTools (F12), go to the Console and paste:

Copy// Lists this page's hreflang tags, flags the common mistakes,
// and checks return links for versions on the same domain
const clean = u => u.split('#')[0];
const loose = u => { try { const x = new URL(u); return (x.origin + x.pathname).replace(/\/$/, '').toLowerCase(); } catch (e) { return u; } };
const here = clean(location.href);
const canonical = document.querySelector('link[rel~="canonical" i]')?.href;
const self = new Set([here, canonical && clean(canonical)].filter(Boolean));
const ALT = 'link[rel~="alternate" i][hreflang]:not([rel~="stylesheet" i])';
const tags = [...document.querySelectorAll(ALT)]
  .map(l => ({ lang: l.getAttribute('hreflang').trim(), raw: (l.getAttribute('href') || '').trim(), href: clean(l.href) }));
const headerAlternates = h => (h || '').split(/,(?=\s*<)/)
  .map(p => p.match(/^\s*<([^>]*)>(.*)$/))
  .filter(m => m && /rel\s*=\s*"?[^";]*\balternate\b/i.test(m[2]) && /hreflang\s*=/i.test(m[2]))
  .map(m => m[1]);
const seen = new Set();
const rows = [];
for (const t of tags) {
  const problems = [];
  const lang = t.lang.toLowerCase();
  if (lang !== 'x-default' && !/^[a-z]{2}(-[a-z]{4})?(-[a-z]{2})?$/i.test(t.lang)) {
    problems.push(/-\d{3}$/.test(t.lang) ? 'number regions such as 419 are not supported' : 'invalid language code');
  }
  if (/-(uk|eu|un)$/i.test(t.lang)) problems.push(/-uk$/i.test(t.lang) ? 'UK is not a region code: use GB' : 'reserved region code: Google ignores it');
  if (!/^https?:\/\//i.test(t.raw)) problems.push(t.raw ? 'not a full URL' : 'no URL');
  if (seen.has(lang)) problems.push('language listed twice');
  seen.add(lang);
  let back = 'other domain: check by hand';
  let status = '';
  if (!t.raw) back = '';
  else if (self.has(t.href)) back = '(this page)';
  else if (t.href.startsWith(location.origin + '/')) {
    try {
      const res = await fetch(t.href, { cache: 'no-store', headers: { Accept: 'text/html' } });
      status = res.status + (res.redirected ? ' → ' + res.url : '');
      const doc = new DOMParser().parseFromString(await res.text(), 'text/html');
      const listed = [...doc.querySelectorAll(ALT)].map(l => l.getAttribute('href') || '')
        .concat(headerAlternates(res.headers.get('link')))
        .map(h => { try { return clean(new URL(h, res.url).href); } catch (e) { return ''; } });
      const near = listed.find(u => [...self].some(s => loose(s) === loose(u)));
      back = !res.ok ? 'page returns ' + res.status
        : listed.some(u => self.has(u)) ? 'yes'
        : near ? 'NO: lists ' + near + ' (not an exact match)' : 'NO';
    } catch (e) { back = 'could not load'; }
  }
  rows.push({ hreflang: t.lang, url: t.href || t.raw, status, 'links back': back, problems: problems.join('; ') || 'none' });
}
if (tags.length && !tags.some(t => t.lang.toLowerCase() !== 'x-default' && self.has(t.href))) {
  rows.push({ hreflang: '(missing)', url: canonical || here, status: '', 'links back': '', problems: 'this page is not in its own list' });
}
console.table(rows.length ? rows : [{ result: 'No hreflang tags in the HTML. Check the HTTP header or the sitemap.' }]);

It lists each hreflang tag with any problems (invalid code, en-UK, unsupported codes such as es-419, relative URL, duplicate language), checks this page is in its own list, and opens each version on the same domain to show its status and whether it links back.

Versions on other domains (such as example.fr) can't be fetched from the Console, so check those by hand. "Links back" needs an exact URL match. If the other page lists a near match, such as a trailing slash or a different query string, the snippet shows it. Run it on the clean URL, without tracking parameters.

2Check the other versions yourself 5 minutes

1. Open each URL from the list in a new tab.
2. View its source (Ctrl+U) and search for hreflang.
3. Check the list is the same set as on the first page, including a line for this version and a line back to the page you started on.
4. Check the page loads directly, with no redirect, and doesn't say noindex.

3If the page shows no tags 2 minutes

The hreflang may be in the HTTP header or the sitemap instead. In DevTools, open Network, reload, click the page's own request and look for a link response header with hreflang in it. If it's not there either, search your XML sitemap for xhtml:link.