RESTCountries.NET is a .NET Standard 2.1 library providing offline access to comprehensive country data. It deserializes an embedded JSON dataset (sourced from restcountries.com) into strongly-typed C# models and exposes static query methods for searching by name, code, currency, language, and more. The library requires no network calls at runtime, making it suitable for disconnected or performance-sensitive applications. It includes a full test suite, a benchmark harness, and is distributed via NuGet with automated CI/CD. The architecture is straightforward: a static `RestCountriesService` class loads data on first access and uses LINQ to answer queries. Models cover Country, Currency, Language, Flags, Maps, Translations, and other attributes. The translation support includes 24 languages via ISO 639-3 codes. Overall, it's a well-crafted, single-purpose utility library with professional engineering practices.