It's recommended. It tells search engines which URL to show users whose locale doesn't match any of your hreflang tags. Usually it's your language selector page or your primary locale.

Should every page link to every other locale?

Yes. Hreflang clusters must be mutually referential: each page lists all alternates, including itself. Missing or one-way links are the most common bug.

Is anything uploaded?

No. Tags are generated locally from your inputs and shown in your browser.

Do I use "en-us" or "en-US"?

Hreflang values are case-insensitive, but "en-US" is conventional (language lowercase, region uppercase) and easier to read. ISO recommends the same.

hreflang · seo · alternate · i18n

Generate hreflang link tags

Build rel=alternate hreflang tags for every language variant. ISO 639-1 codes, optional ISO 3166 region. All assembly runs locally.

Hreflang Generator

Languages

variants

x-default

set

fallback

Length

272 B

272 chars

Status

live

ready

input · variants

ISO 639-1 lang optionally with ISO 3166 region — e.g. en, en-US, zh-Hant. Include x-default for the fallback.

output · link tags

<link rel="alternate" hreflang="en" href="https://example.com/">
<link rel="alternate" hreflang="es" href="https://example.com/es/">
<link rel="alternate" hreflang="fr" href="https://example.com/fr/">
<link rel="alternate" hreflang="x-default" href="https://example.com/">

Quick Start

How to declare hreflang

Hreflang annotations tell search engines which URL to serve which audience. Every page must reference every variant including itself.

01
List variants
Add a row for each language/region — both the language code and absolute URL.
Lookups reference the IANA registries (MIME, HTTP status, TLDs) bundled at build time — no live network calls, no rate limits, no leaked queries.
listIANAregistryofflinelive
variants · query4 · IANA
```
en, es, fr, x-default
```
loaded · IANA bundlespec · ready
02
Include x-default
Fallback for browsers that don't match any specific code — usually the English version.
Builders emit canonical syntax per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs) so the output passes spec-compliant parsers.
defaultRFC 9110canonicalspec-compliantlive
x-default · optionsset · live
```
hreflang="x-default"
```
options applied · livecanonical
03
Self-reference
Each variant page must list every variant — including itself.
Validation flags common pitfalls — uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8 — before they bite production.
selfvalidationlintpitfallslive
self-ref · looked upyes · ready
```
<link … hreflang="es" …>
```
result · livevalidated
04
Place in head
Drop the link tags into <head> on every variant — or send via HTTP Link header.
Copy writes the snippet directly into your clipboard; downloads emit the right extension and MIME so curl/httpie pick them up correctly.
shipclipboardMIME-correctblobcurl-ready
ok · copiedhead · done
```
✓ Copied
```
shipped · ready to shipsuccess

Pro tips

Web-spec details that bite later

Idempotency saves retries

POST/PUT/DELETE should be safely retried. Use idempotency keys and return the same response on duplicate requests.

Match RFC 9110 status codes

Don’t invent codes. 422 for validation errors, 409 for conflicts, 429 for rate limits. Standard codes work with off-the-shelf clients.

Set <code>Cache-Control</code> deliberately

Default browser caching is conservative. Use max-age + stale-while-revalidate for hot endpoints.

Validate Open Graph in dev

OG tags break silently. Use a previewer like OG Generator + Facebook’s debugger before launch.

CORS is a server concern

The browser sends the preflight; the server decides. Wildcard origins disable credentials — be explicit.

MIME drives behaviour

Servers must send the right Content-Type. Browsers sniff but the spec says they shouldn’t — be explicit to avoid surprises.

Use Cases

When to declare hreflang

Internationalisation, regional SEO, multi-locale sites.

Multi-locale

Show es-MX vs es-ES variants to the right audience. Bundled from IANA registries at build time — no live network call, no rate limit, no leaked queries. The MIME, TLD, and status-code tables are baked in so the tool works offline once loaded.

spec-compliant

ccTLD/Subfolder

Annotate /en/ vs /es/ paths regardless of structure. Output is canonical per the relevant RFC (9110 for HTTP, 5322 for headers, 3986 for URLs), so spec-compliant parsers accept it as-is. Cross-browser and cross-library behaviour stays consistent.

offline

Editorial regions

Hreflang prevents duplicate-content penalties. Pairs with the curl-to-fetch converter for end-to-end test stubs — copy the curl from DevTools, paste, get an idiomatic fetch() body. Drop into Playwright/Vitest fixtures without manual translation.

IANA-backed

Currency switch

Different price/locale pages need self-referencing tags. Catches common pitfalls (uppercase header names, smart quotes inside Content-Type, missing ;charset=utf-8) before they bite production. Validation flags rather than auto-corrects so you stay in control.

RFC-aligned

Migration

Verify variants link to each other after a re-platform. Validation runs as you type — copy only when the output is shaped correctly. The output drops directly into nginx, Apache, or CDN configs without re-formatting or re-quoting.

production-grade

x-default fallback

Catch-all language for non-matching visitors. Same input plus same options always produces identical canonical output, so the tool is safe to embed in CI scripts that diff against expected configs.

curl-ready

FAQ

Frequently asked questions

Do all variants need the same tags?

Yes — every page must list every other variant (and itself). Asymmetric annotations are ignored by Google.

Language code casing?

Convention is lowercase language, uppercase region (en-US). Search engines accept any case but consistency helps debugging.

Hreflang vs canonical?

Canonical picks the master URL; hreflang annotates variants. Each variant's canonical should point to itself, not the English version.

What about HTTP Link header?

Useful for non-HTML resources (PDFs). Same syntax, sent as Link: <url>; rel=alternate; hreflang=es.

Is anything sent to a server?

No — tag generation runs locally in your browser.

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