In software development, obfuscation is the practice of creating source or machine code that is intentionally difficult for humans or computers to understand. Similar to obfuscation in natural language, code obfuscation may involve using unnecessarily roundabout ways to write statements. Programmers may obfuscate code to conceal its purpose, logic, or embedded values. The primary reasons for doing so are to prevent tampering, deter reverse engineering, or to create a puzzle or recreational challenge to deobfuscate the code, a challenge often included in crackmes. While obfuscation can be done manually, it is more commonly performed using obfuscators.

The architecture and characteristics of some languages may make them easier to obfuscate than others. C, C++, and the Perl programming language are some examples of languages easy to obfuscate. Haskell is also quite obfuscatable despite being quite different in structure.

The properties that make a language obfuscatable are not immediately obvious.

Types of obfuscations include simple keyword substitution, use or non-use of whitespace to create artistic effects, and self-generating or heavily compressed programs.

According to Nick Montfort, techniques may include:

A variety of tools exist to perform or assist with code obfuscation. These include experimental research tools developed by academics, hobbyist tools, commercial products written by professionals, and open-source software. Additionally, deobfuscation tools exist, aiming to reverse the obfuscation process.

While most commercial obfuscation solutions transform either program source code or platform-independent bytecode, i.e. portable code (as used by Java and .NET), some also work directly on compiled binaries.

Writing and reading obfuscated source code can be a brain teaser. A number of programming contests reward the most creatively obfuscated code, such as the International Obfuscated C Code Contest and the Obfuscated Perl Contest.