LangTest Pro is a free Chrome extension designed to assist users in detecting the presence of specific languages on webpages. By entering a language code, such as 'en' for English or 'es' for Spanish, users can analyze the language composition of any webpage, making it an invaluable tool for localization testing and content analysis. This extension is particularly useful for ensuring the accuracy of multilingual websites by highlighting words that match the specified language, facilitating visual verification of language presence.

The extension utilizes the langid library to detect languages within the text, including content rendered through JavaScript. It operates by sending website URLs to a secure server for analysis, which then returns detailed language data back to the extension. This process ensures that users receive accurate information regarding the language distribution on their chosen webpages, making it an effective tool for developers and content managers.