Multilingual programmatic unit-conversion site with SEO-ready sitemaps

The challenge

A European web agency ran a small utility website with temperature-conversion pages, each value served as its own page. The agency wanted the same approach rolled out across many more conversions, such as steps to kilometres, kilograms to pounds and inches to pixels, so that each value had a unique, indexable page.

The site is written in plain PHP without a framework, so the page-generation logic had to be replicated by hand for every new converter. The agency also wanted the site to reach other language markets, which meant language-prefixed URLs and correct signals to search engines about which page belongs to which language. Without that groundwork, thousands of near-identical pages risk being treated as duplicates.

What we did

• New converters. We replicated the existing page-generation logic for a range of new unit pairs, so each conversion value produces its own page with readable, hyphenated URLs.
• Multilingual URLs. We added language-prefixed paths (for example a Spanish `/es/` section) and set the correct `html lang` attribute on every page.
• Technical SEO. We generated split sitemaps with hreflang alternates and added `rel="canonical"` tags, so search engines can crawl the large page set and understand language variants.
• Deployment for review. We deployed the build to a development folder on the live domain and to a separate test domain, so the agency could check it before release.
• Post-launch fixes. After the agency's review we corrected the language switcher, canonical tags and broken links.

Tech stack

PHP, .htaccess rewrites, XML sitemaps with hreflang