Codification is the defining feature of civil law jurisdictions. In common law systems, such as that of English law, codification is the process of converting and consolidating judge-made law into statute law.   
Ancient Sumer's Code of Ur-Nammu was compiled circa 2050–1230 BC, and is the earliest known surviving civil code. Three centuries later, the Babylonian king Hammurabi enacted the set of laws named after him.
Besides religious laws such as the Torah, important codifications were developed in the ancient Roman Empire, with the compilations of the Lex Duodecim Tabularum and much later the Corpus Juris Civilis. These codified laws were the exceptions rather than the rule, however, as during much of ancient times Roman laws were left mostly uncodified.
The first permanent system of codified laws could be found in China, with the compilation of the Tang Code in AD 624. This formed the basis of the Chinese criminal code, which was then replaced by the Great Qing Legal Code, which was in turn abolished in 1912 following the Xinhai Revolution and the establishment of the Republic of China. The new laws of the Republic of China were inspired by the German codified work, the Bürgerliches Gesetzbuch.  A very influential example in Europe was the French Napoleonic code of 1804.
Another early system of laws is Hindu law framed by Manu and called as Manu Smriti, dating back to the 2nd century BC. The use of civil codes in Islamic Sharia law began with the Ottoman Empire in the 16th century AD.
Civil law jurisdictions rely, by definition, on codification. A notable early example were the Statutes of Lithuania, in the 16th century. The movement towards codification gained momentum during the Enlightenment, and was implemented in several European countries during the late 18th century (see civil code). However, it only became widespread after the enactment of the French Napoleonic Code (1804), which has heavily influenced the legal systems of many other countries.
Common law has been codified in many jurisdictions and in many areas of law: examples include criminal codes in many jurisdictions, and include the California Civil Code and the Consolidated Laws of New York ( New York State).
The English judge Sir Mackenzie Chalmers is renowned as the draftsman of the Bills of Exchange Act 1882, the Sale of Goods Act 1893 and the Marine Insurance Act 1906, all of which codified existing common law principles. The Sale of Goods Act was repealed and re-enacted by the Sale of Goods Act 1979 in a manner that revealed how sound the 1893 original had been.  The Marine Insurance Act (mildly amended) has been a notable success, adopted verbatim in many common law jurisdictions. So, it is surprising that the British Parliament has failed to continue this proven practice of taking settled common law and converting it into an up-to-date handy booklet, accessible to practitioners and the general public alike. Nor has Parliament even bothered to update either the Sale of Goods Act 1979 nor the Marine Insurance Act, instead passing blockbuster statutes such as the Consumer Rights Act 2015 and the Insurance Act 2015 which (respectively) modify the codifying statutes without bringing out "new editions" thereof. It follows that the only easy way to keep up to date on existing legislation is to use either the internet or books of materials which publish the statutes (as amended).
Most of England's criminal laws have been codified, partly because this enables precision and certainty in prosecution. However, large areas of the common law, such as the law of contract and the law of tort remain remarkably untouched. In the last 80 years there have been statutes that address immediate problems, such as the Law Reform (Frustrated Contracts) Act 1943 (which. inter alia, coped with contracts rendered void by war), and the Contracts (Rights of Third Parties) Act 1999, which amended the doctrine of Privity. However, there has been no progress on the adoption of Harvey McGregor's "Contract Code" 1993, even though the Law Commission, together with the Scots Law Commission, asked him to produce a proposal for the comprehensive codification and unification of the contract law of England and Scotland. Similarly, codification in the law of tort has been at best piecemeal, a rare example of progress being the Law Reform (Contributory Negligence) Act 1945.
In the United States, acts of Congress, such as federal statutes, are published chronologically in the order in which they become law – often by being signed by the President, on an individual basis in official pamphlets called " slip laws", and are grouped together in official bound book form, also chronologically, as " session laws". The "session law" publication for Federal statutes is called the United States Statutes at Large. Any given act may be only a single page, or hundreds of pages, in length. An act may be classified as either a "Public Law" or a "Private Law".
Because each Congressional act may contain laws on a variety of topics, many acts, or portions thereof are also rearranged and published in a topical, subject matter codification by the Office of the Law Revision Counsel. The official codification of Federal statutes is called the United States Code. Generally, only "Public Laws" are codified. The United States Code is divided into "titles" (based on overall topics) numbered 1 through 54.  Title 18, for example, contains many of the Federal criminal statutes. Title 26 is the Internal Revenue Code. 
Even in code form, however, many statutes by their nature pertain to more than one topic. For example, the statute making tax evasion a felony pertains to both criminal law and tax law, but is found only in the Internal Revenue Code.  Other statutes pertaining to taxation are found not in the Internal Revenue Code but instead, for example, in the Bankruptcy Code in Title 11 of the United States Code, or the Judiciary Code in Title 28. Another example is the national minimum drinking age, not found in Title 27, Intoxicating liquors, but in Title 23, Highways, §158.
Further, portions of some Congressional acts, such as the provisions for the effective dates of amendments to codified laws, are themselves not codified at all. These statutes may be found by referring to the acts as published in "slip law" and "session law" form. However, commercial publications that specialize in legal materials often arrange and print the uncodified statutes with the codes to which they pertain.
In the United States, the individual states, either officially or through private commercial publishers, generally follow the same three-part model for the publication of their own statutes: slip law, session law, and codification.
Rules and regulations that are promulgated by agencies of the Executive Branch of the United States Federal Government are codified as the Code of Federal Regulations. These regulations are authorized by specific enabling legislation passed by the legislative branch, and generally have the same force as statutory law.
Following the First World War and the establishment of the League of Nations, the need for codification of international law arose. In September 1924, the General Assembly of the League established a committee of experts for the purpose of codification of international law, which was defined by the Assembly as consisting of two aspects:
- Putting existing customs into written international agreements
- Developing further rules
In 1930 the League of Nations held at the Hague a conference for the purpose of codification of rules on general matters, but very little progress was made.
Following the Second World War, the International Law Commission was established within the United Nations as a permanent body for the formulation of principles in international law.
Recodification refers to a process where existing codified statutes are reformatted and rewritten into a new codified structure. This is often necessary as, over time, the legislative process of amending statutes and the legal process of construing statutes by nature over time results in a code that contains archaic terms, superseded text, and redundant or conflicting statutes. Due to the size of a typical government code, the legislative process of recodification of a code can often take a decade or longer.
- Yale article on codification 
- Lord Scarman on codification 
- Sauveplanne article on codification 
- Chinese law
- For the most part, the Sale of Goods Act 1979 retains the wording and section numbers of its 1893 predecessor.
- Public Law No: 113-287, To enact title 54, United States Code, "National Park Service and Related Programs", as positive law.
- USC table of contents
- see 26 USC 7201