How is a written constitution different from an uncodified constitution?

It is a common misconception that countries like the United Kingdom have an "unwritten" constitution. In reality, scholars prefer the term uncodified, as many parts of the British constitution exist in written form through various statutes and documents.1

The primary differences between written (codified) and uncodified constitutions include:

• Formal Documentation: A written constitution is contained within a single, formal document (such as the U.S. Constitution), whereas an uncodified constitution lacks a single, comprehensive document and is instead composed of various statutes, judicial doctrines, and conventions.1
• Judicial Review: Countries with written constitutions often empower an independent judiciary to perform judicial review, allowing courts to nullify legislation deemed incompatible with constitutional principles. Conversely, countries with uncodified constitutions, such as the U.K., typically operate under the principle of "parliamentary supremacy," where courts cannot invalidate acts of Parliament.2
• Flexibility: Uncodified constitutions are generally "flexible," meaning constitutional rules can be modified through the same procedures used for ordinary legislation. Many written constitutions are "rigid," requiring special procedures or supermajorities to amend.1

Regardless of classification, no written constitution is entirely exhaustive; all are supplemented by practices, judicial interpretations, and political norms.1