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 1,320,418

174,846

India 439,882

77,587

United Kingdom 404,005

65,581

Brazil 411,231

43,920

Germany 391,462

63,127

France 311,727

54,266

Italy 291,018

56,155

Canada 298,167

46,748

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, Aug 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