Minification Measurements

Why This Matters: Data Over Opinions

This project provides real-world context to the extended Twitter thread about JavaScript bundle sizes and minification. While opinions from famous developers are interesting, actual metrics tell the real story.

Why initial download size matters:

• First impressions count: First Contentful Paint (FCP) directly impacts user perception and bounce rates
• Mobile networks: Many users worldwide still rely on 3G/4G with data caps and slower speeds
• Core Web Vitals: Google uses Largest Contentful Paint (LCP) as a ranking factor, which is affected by JavaScript download time
• Parse/compile time: Larger files take longer to parse and execute, blocking the main thread
• Cache misses: First-time visitors and cache invalidation mean the full download happens more often than we think

It's surprising when library authors who advocate for simplicity don't prioritize minification. While philosophies like "locality of behavior" and sending HTML over the wire are excellent for reducing complexity, why not also reduce the bytes? A 63.5% size reduction (or 50% with brotli) is significant, especially when every millisecond counts for user experience.

The measurements on this site show that minification isn't just a "nice to have" — it's a substantial optimization that can dramatically improve load times, especially on slower connections. When choosing libraries, both architecture AND delivery optimization matter.

Note on methodology: All test pages are intentionally written in raw JavaScript without any framework dependencies. This attempts to eliminate any potential cache bias that could occur from using the libraries being tested to build the test harness itself, trying to show clean and accurate measurements.

The Universal Truth About Performance

This video about game optimization makes most of the arguments for me. While it's targeted at game development, the same ideas are 100% applicable to web development. Whether you're shipping game assets or JavaScript libraries, the principles remain constant: smaller downloads mean faster loads, better user experience, and broader accessibility.

The video highlights how even small optimizations compound into significant performance gains. In web development, this translates directly: a 63.5% reduction in file size isn't just a number — it's the difference between a user staying on your site or bouncing, between passing Core Web Vitals or failing, between accessibility for users on limited data plans or exclusion.