Fastify vs Express: source lines of code compared
As of 2026-07-27, fastify/fastify contains 14,751 total lines (10,978 code) across 81 files, while expressjs/express contains 9,401 total lines (2,617 code) across 70 files as of 2026-07-13. fastify/fastify is about 4.2x the size of expressjs/express by code lines. Code size is not code quality: a larger count only means more source material, not a better or worse project.
Top languages in fastify/fastify: JavaScript (74.4% of code), TypeScript (23.4% of code), JSON (2.1% of code). Top languages in expressjs/express: JavaScript (90.4% of code), JSON (3.8% of code), Handlebars (2.7% of code). JavaScript, JSON appear in both top language lists; TypeScript, Shell, Markdown appear only in fastify/fastify's top languages; Handlebars, CSS, HTML appear only in expressjs/express's top languages.
Methodology: both counts come from cached OctoCounts reports generated with tokei. fastify/fastify was counted at ref main (commit 325682c9e5ab) on 2026-07-27; expressjs/express was counted at ref master (commit ae6dd37680e3) on 2026-07-13. See the counting methodology for ignored directories and analysis options.
Evidence and next steps:
Note: code size is not code quality. OctoCounts only reports reproducible line counts and makes no claim that either project is better.