Software Engineering at Google

Chapter 17. Code Search

Written by Alexander Neubeck and Ben St. John

Edited by Lisa Carey

Code Search is a tool for browsing and searching code at Google that consists of a frontend UI and various backend elements. Like many of the development tools at Google, it arose directly out of a need to scale to the size of the codebase. Code Search began as a combination of a grep-type tool¹ for internal code with the ranking and UI of external Code Search.² Its place as a key tool for Google developers was cemented by the integration of Kythe/Grok,³ which added cross-references and the ability to jump to symbol definitions. 

That integration changed its focus from searching to browsing code, and later development of Code Search was partly guided by a principle of “answering the next question about code in a single click.” Now such questions as “Where is this symbol defined?”, “Where is it used?”, “How do I include it?”, “When was it added to the codebase?”, and even ones like “Fleet-wide, how many CPU cycles does it consume?” are all answerable with one or two clicks.

In contrast to integrated development environments (IDEs) or code editors, Code Search is optimized for the use case of reading, understanding, and exploring code at scale. To do so, it relies heavily on cloud-based backends for searching content and resolving cross-references.

In this chapter, we’ll look at Code Search in more detail, including how Googlers use it as part of their developer workflows, why we chose to ...