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core-js vs Day.js

Based on 2041 and 14 real audits

View core-js details | View Day.js details
Metriccore-jsDay.jsWinner
Performance3740Day.js
Accessibility8878core-js
Best Practices8683core-js
SEO9192Day.js
Security6868Tie
TTFB483ms475msDay.js
Composite7475Day.js
Performance
core-js
37
Day.js
40
Accessibility
core-js
88
Day.js
78
Security
core-js
68
Day.js
68
SEO
core-js
91
Day.js
92
Composite
core-js
74
Day.js
75

Day.js outperforms core-js in 4 of 7 categories, with a stronger composite score (75 vs 74). core-js leads in accessibility, best practices.

When to choose core-js

Choose core-js when your primary concern is accessibility and best practices. Its audit data shows consistent strength in these areas across the sampled sites.

When to choose Day.js

Choose Day.js when your primary concern is server response time and performance. Its audit data shows consistent strength in these areas across the sampled sites.

How this comparison was built

Scores are medians across 2041 audited core-js sites and 14 audited Day.js sites in the BeaverCheck database. Every audit runs the same 100+ checks — Lighthouse performance, security headers, accessibility, SEO, server response time — against a real URL. No vendor input, no sponsorship, no affiliate links. Read the full methodology →

FAQ

Which is faster, core-js or Day.js?
Based on real BeaverCheck audits, Day.js sites score higher on Lighthouse performance (40 vs 37 on average).
Which has better security, core-js or Day.js?
core-js sites score higher on security analysis (68 vs 68 on average).
Which has better accessibility, core-js or Day.js?
Accessibility scores measured by Lighthouse WCAG 2.1 checks favor core-js (88 vs 78). Both technologies can be made fully accessible with care — the difference reflects common patterns in the sampled sites, not inherent platform limits.
Which is better for SEO, core-js or Day.js?
Day.js sites score higher on Lighthouse SEO signals (92 vs 91 on average), which cover meta tags, crawlability, mobile friendliness, and structured data. Content strategy and backlinks still matter more than platform choice for ranking.
Which has faster server response (TTFB), core-js or Day.js?
Day.js sites show lower Time to First Byte (475 ms vs 483 ms on average). TTFB depends heavily on hosting and CDN setup rather than the technology itself, but the sampled sites suggest a meaningful difference in common deployment patterns.
Should I choose core-js or Day.js for my website?
Both platforms have trade-offs. Day.js scores higher on overall composite score while core-js may excel in metrics you care about most. Run a free BeaverCheck audit on a real site using each to compare the metrics relevant to your use case.
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