Uncompressed Size

Uncompressed Size is the total file size of web assets (HTML, CSS, JavaScript, images) before any compression algorithms like Gzip or Brotli are applied.

Meaning & Context

This metric represents the raw size of resources that browsers must parse and process after decompression, even though they're transmitted in compressed form. While compressed size affects network transfer time, uncompressed size impacts parsing, compilation, and execution performance. The ratio between compressed and uncompressed size indicates compression efficiency, typically ranging from 3:1 to 10:1 for text-based assets.

Why It Matters

In A/B testing, tracking uncompressed size helps identify variants that add significant JavaScript or CSS overhead, which can slow down page interactivity even with good network performance. Large uncompressed files require more CPU time to parse and execute, particularly impacting mobile devices with limited processing power. This metric is especially important when testing variants that include additional tracking scripts, personalization engines, or interactive features.

Example

A test variant that adds a new recommendation widget appears to load quickly due to good compression, but analysis reveals 450KB of uncompressed JavaScript that causes a 2-second delay in Time to Interactive on mobile devices, leading to lower engagement despite successful initial loading.