core-js vs Underscore.js

Head-to-head usage across the sites we track.

Top sites by authority

core-js · Underscore.js · how many of each technology's sites sit in the web's highest authority tiers

Open Page Rank scores 0 to 10 from the open web link graph; 9+ covers only a few hundred domains worldwide.

By country

core-js · Underscore.js · share of sites in each country using one or the other

United States 1,479,835

196,685

India 495,926

88,983

United Kingdom 457,421

74,584

Germany 439,161

71,501

Brazil 420,075

48,901

France 369,824

65,402

Italy 336,371

65,347

Canada 341,001

53,918

Audience countries from the Chrome UX Report, top markets of either technology.

Real user performance

Median site's p75 values from the Chrome UX Report, Jun 2026. Lower is better; green meets Google's "good" threshold. This describes the sites that use each technology, not the technology's own overhead.

Sites that switched

Domains that dropped one technology and adopted the other within about a year, data nobody else gives away free.

All core-js sites · All Underscore.js sites