livegrep Code Search

livegrep is an open-source, interactive, real-time code search tool that provides fast regex search across large repositories. Originally developed at Nelson Elhage and used internally at Square (now Block), livegrep has over 1,400 stars as of 2026. Unlike traditional grep that searches files sequentially, livegrep pre-indexes repositories into a global index that supports instant regex searches with results updating as you type, providing a Google-instant-like search experience for source code. Key features include: instant search (results appear in real-time as you type, with sub-100ms query latency even across millions of lines of code via a pre-built inverted index), regex support (full POSIX regex syntax with case-sensitive and case-insensitive modes, supporting capturing groups, character classes, anchors, and quantifiers), multi-repository search (indexing and searching across multiple repositories simultaneously, with repository name filtering and result grouping), web interface (a responsive web UI displaying search results with syntax highlighting, file names, line numbers, and contextual code snippets), gRPC and HTTP API (programmatic access for integrating code search into IDEs, bots, and developer tools), repository management (adding, updating, and removing repositories from the index, with automatic re-indexing on repository updates), Git integration (cloning and indexing Git repositories directly, supporting GitHub, GitLab, Bitbucket, and any Git remote), file type filtering (searching only within specific file extensions or directories), code preview (browsing full file contents from the search results without leaving the interface), and high performance (written in C++ with a custom index format optimized for read-heavy workloads).