Email marketing impact React sites
Performance impact by email_marketing provider.
1
At a glance the headline numbers for Email marketing impact
Performance impact by email_marketing provider.
3
Providers ranked
After min-sites filter
290
Sites in sample
Combined across all items
0.04
Best CLS (p75)
Klaviyo
The State of Web Vitals · October 2026 · React sites (9,570) · all devices field datacorewebvitals.io/state-of-cwv
2
The ranking sorted by CLS at p75, fastest first
| # | Provider | CLS p75 | Passing | Sites | |
|---|---|---|---|---|---|
| 1 | Klaviyo | 0.04 | 88.4% | 70 | |
| 2 | HubSpot | 0.07 | 80.9% | 90 | |
| 3 | Mailchimp | 0.07 | 80.6% | 130 |
The State of Web Vitals · October 2026 · React sites (9,570) · all devices field datacorewebvitals.io/state-of-cwv
3
Passing CLS per provider which group passes the CLS most often
ProviderSitesPassing CLSp75
Salesforce Marketing Cloud 0.1% 8 0.09
Klaviyo 0.7% 70 0.04
HubSpot 0.9% 90 0.07
Mailchimp 1.4% 130 0.07
ActiveCampaign 0.2% 15 0.08
Good Needs Improvement Poor Sorted best-passing first · median colored by its own rating · pass = good CLS (0.1 at p75) · one value per site
The State of Web Vitals · October 2026 · React sites (9,570) · all devices field datacorewebvitals.io/state-of-cwv
4
All five vitals at once the whole category without toggling - cell is the pass rate, small number the p75
LCP
INP
CLS
FCP
TTFB
Mailchimp 1.4%
483.2s
97108ms
810.07
432.7s
242.5s
HubSpot 0.9%
643.3s
96120ms
810.07
582.6s
422.0s
Klaviyo 0.7%
732.6s
97128ms
880.04
702.0s
431.8s
ActiveCampaign 0.2%
642.6s
100156ms
790.08
572.2s
291.9s
Salesforce Marketing Cloud 0.1%
1002.0s
25278ms
1000.09
631.8s
50932ms
60%95%+ passing Cell: pass rate, small number = p75 · faded rows: under 100 sites
One row per provider, one column per vital - the cell is the share of sites passing, the small number the p75. No toggling needed to see where the category actually differs.
The State of Web Vitals · October 2026 · React sites (9,570) · all devices field datacorewebvitals.io/state-of-cwv
Related signals Font services (4) → Session recording (11) → CMS (17) → Search (6) → 210,902 crawled sites with Chrome field data, representing millions of real page loads · How we measured
210,902 crawled sites with Chrome field data, representing millions of real page loads. How we measured.