transpile

Transpile is a portmanteau of transform and compile. In software development, it refers to translating source code written in one programming language into source code in another language at the same or a higher abstraction level, rather than compiling to machine code directly. The goal is to allow developers to write code using newer language features or different syntax and run it in environments that do not natively support them. A transpiler typically performs a source-to-source transformation: the input is parsed into an abstract syntax tree, various transformations are applied, and new source code is generated in the target language. Unlike a traditional compiler that produces executable machine code, a transpiler often targets another high-level language or a form of intermediate representation that can be further processed.

Common use cases include converting modern JavaScript (ES6+) into widely supported JavaScript versions for older runtimes, enabling experimental or domain-specific languages, and porting code between language ecosystems (for example TypeScript to JavaScript, CoffeeScript to JavaScript, or Kotlin to JavaScript). Transpilers may preserve semantics while adapting features, or they may replace unsafe constructs with safer equivalents; some perform optimizations or polyfills to emulate missing standard library features.

Criticism of transpilers includes potential loss of readability, debugging difficulties, and reliance on tooling. Proponents argue transpilers extend longevity of codebases and enable progressive enhancement of language features. Modern toolchains often integrate transpilation with bundling, linting, and testing.