How do you build a bilingual (PL/EN) website that ranks?

A bilingual Polish/English site ranks when both versions are fully translated and separately optimised on one domain, with Polish at the root and English at /en/, and when correct hreflang tags link the two versions in both directions. Translated pages are not duplicate content. Done right, they share ranking signals, so a strong English page can lift its Polish twin (Google Search Central, 2025).

Get the details wrong and Google can struggle to index either language properly.

Why bother with two languages at all?

Poland is a big online market. It had 35.75 million internet users at 88.1% penetration as of January 2024 (DataReportal, Digital 2024: Poland), and Google holds roughly 96–97% of search there (StatCounter). Poland is also in the "High Proficiency" band of the EF English Proficiency Index, especially among under-35s, so part of your audience will happily search and buy in English.

Two languages let you reach both groups, but each version still has to earn its own rankings.

Subdirectory, subdomain, or separate domain?

For almost every business with two languages, use subdirectories on one domain: twojafirma.pl/ for Polish and twojafirma.pl/en/ for English.

Google lists subdirectories, subdomains and country-code domains as valid options, but calls URL parameters like ?lang=en "not recommended" (Google Search Central, 2025). Subdirectories suit a small site because one domain collects every backlink and share, so authority builds on a single property instead of being split across two. Subdomains and separate .pl / .com domains make sense only at large scale or for brands that really are separate.

What is hreflang, and why does it matter for ranking?

hreflang is a small tag in each page's <head> that tells Google "here is the same page in another language." It's how Google knows your Polish and English pages belong together as a pair.

Correct hreflang lets the two versions support each other. Errors can make Google treat them as competitors or ignore the connection entirely, and they're common:

An Ahrefs study across 374,756 domains found that 67% of hreflang implementations contain errors, most often missing return links, wrong language codes, or pointing at the wrong URL (Ahrefs).

The rules that prevent those errors are simple, but each one has to be followed exactly:

Links go both ways. If the Polish page points to the English one, the English one must point back. One-way tags are silently ignored (Google Search Central, 2025).
Each page lists itself in its own hreflang set.
URLs are fully qualified (https://...) and point only to canonical pages.
An x-default covers everyone whose language is neither Polish nor English. This is usually the English version.

We validate hreflang at build time, so a missing return link can't go live unnoticed.

Does translated content count as duplicate content?

No. It's a common worry, and Google answers it plainly: "Localized versions of a page are only considered duplicates if the main content of the page remains untranslated" (Google Search Central, 2025). Fully translated pages are distinct content.

Around 29% of the web is duplicate content, and Google handles legitimate cases algorithmically without a penalty (Moz). Translations properly linked with hreflang also share ranking signals, so strength in one language lifts the other (Ahrefs).

What does cause harm: half-translated pages (a Polish body with English buttons), identical untranslated text served at two URLs, or thin machine translation nobody reviewed. If you can't translate a page properly, leave it in one language.

Should the site detect a visitor's language and redirect them?

No. Google says so directly: "Avoid automatically redirecting users" between language versions (Google Search Central, 2025). Auto-redirects can trap people on VPNs, travellers and anyone on a shared computer in the wrong language. Googlebot crawls from US IP addresses, so a redirect may stop it from ever reaching your Polish content.

Suggest the other language and let the visitor choose. Detect the browser language and show a small banner they can dismiss ("Looking for English?"). Once the visitor picks a language, the URL carries that choice.

Where does the language switcher go?

In the header first, with the footer as a fallback. Most users look for language controls at the top of the page and only check the footer if they can't find them there (Smashing Magazine, 2022). We follow a few rules on every build:

Label the languages with their native names, "Polski" and "English", instead of abbreviations. Chrome's auto-translate can turn "PL" / "EN" into gibberish, and full words don't have that problem.
Don't use flags. Flags represent countries rather than languages.
Keep it outside the mobile hamburger menu, with a tap target of at least 44×44px (WCAG 2.5.8).

FAQ

Should Polish or English be at the root URL? Whichever language your main audience uses. For a Poland-first business, Polish goes at the root and English at /en/. For an international product, flip it. Both setups work as long as the structure matches where your customers are.

Do I need to translate every blog post into both languages? No. Translate cornerstone pages (services, key posts) into both, and publish language-specific posts beyond that. Polish and English buyers search for different things, so separate editorial calendars are fine. Just don't show a "switch to English" link that leads to a page that doesn't exist.

Do AI search engines like ChatGPT and Google AI Overviews need special markup? No. Google says to apply "the same foundational SEO best practices for AI features as you do for Google Search overall" (Google Search Central, 2025). AI engines are language-aware, so Polish queries draw on Polish content and English queries on English content. Optimise both versions and add inLanguage to your structured data. There's no separate AI step.

Can I just machine-translate the whole site? You can, but unreviewed machine translation reads as thin content and can trip quality signals. Translate factual pages directly. Persuasive copy needs transcreating, because Polish business writing is more formal than English and a literal CTA often lands wrong.

We settle the URL structure of a Polish/English site before writing any code. You can book a call to work out the right structure for your business, including which pages need both languages.