core-js vs Slimbox
Head-to-head usage across the sites we track.
Top sites by authority
core-js · Slimbox · how many of each technology's sites sit in the web's highest authority tiers
Open Page Rank 9+
242
3
Open Page Rank 8+
5,108
19
Open Page Rank 7+
26,213
33
Open Page Rank 6+
57,082
47
Open Page Rank 5+
109,074
70
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 · Slimbox · share of sites in each country using one or the other
United States
1,479,835
231
India
495,926
131
United Kingdom
457,421
154
Germany
439,161
592
Brazil
420,075
85
France
369,824
215
Canada
341,001
83
Italy
336,371
202
Audience countries from the Chrome UX Report, top markets of either technology.
Real user performance
| Metric | core-js | Slimbox |
|---|---|---|
| LCP | 2 s | 1.5 s |
| INP | 75 ms | 75 ms |
| CLS | 0 | 0 |
| TTFB | 800 ms | 600 ms |
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.