Bootstrap vs Flat UI
Head-to-head usage across the sites we track.
Top sites by authority
Bootstrap · Flat UI · how many of each technology's sites sit in the web's highest authority tiers
Open Page Rank 9+
184
1
Open Page Rank 8+
3,816
13
Open Page Rank 7+
18,496
25
Open Page Rank 6+
38,723
35
Open Page Rank 5+
71,693
50
Open Page Rank scores 0 to 10 from the open web link graph; 9+ covers only a few hundred domains worldwide.
By country
Bootstrap · Flat UI · share of sites in each country using one or the other
United States
758,929
311
India
368,409
205
Germany
277,428
145
United Kingdom
255,833
219
Brazil
241,343
119
France
234,434
120
Italy
222,549
131
Spain
183,194
145
Audience countries from the Chrome UX Report, top markets of either technology.
Real user performance
| Metric | Bootstrap | Flat UI |
|---|---|---|
| LCP | 1.8 s | 2 s |
| INP | 75 ms | 75 ms |
| CLS | 0 | 0 |
| TTFB | 800 ms | 900 ms |
Median site's p75 values from the Chrome UX Report, Sep 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.
Bootstrap to Flat UI
| Domain | When |
|---|---|
| fondofasa.it | Aug 2026 |
| wisconsinhealthnews.com | Nov 2025 |
Flat UI to Bootstrap
| Domain | When |
|---|---|
| fondofasa.it | Aug 2026 |
| wisconsinhealthnews.com | Nov 2025 |