The State of Web Vitals

Third-party domains

How many distinct third-party domains the page contacts.

Field data PhoneDesktopAll Scope All sites Q1 2026 edition · Phone field outcomes
Metric LCP INP CLS
1

At a glance the headline numbers for Third-party domains

How many distinct third-party domains the page contacts.

7
on the typical site
half of sites sit at or below
11
1 in 4 sites exceed this
the top quarter
36
the heaviest 1%
the long tail
94,910
sites measured
phone field data

The typical site contacts 7 third-party domains. The heaviest 1% contact 36 or more.

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
2

Distribution & median CLS site count and median CLS at each level of third-party domains

0.00 0.04 0.08 0.11 0.15
0.1
0 10040 20080
0 1 2 3 4 5 6–8 9–11 12–15 16–21 22–29 >p98
Good (≤0.1) Needs improvement Poor (>0.25) Site count
The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
3

Passing CLS by third-party domains which level passes the CLS most often

Third-party domainsSitesPassing CLSCLS
1 7,695 94% 0.00
2 7,681 91% 0.00
3 7,611 91% 0.00
4 7,704 89% 0.00
5 7,147 92% 0.00
6–8 20,080 89% 0.00
9–11 14,993 88% 0.00
12–15 10,704 87% 0.00
16–21 6,507 85% 0.00
22–29 2,900 84% 0.01
>p98 1,885 81% 0.02
Good Needs Improvement Poor Faded rows: under 100 sites

Third-party domains 7. p75 11. p99 36. Spearman with CLS r = +0.30. At the low end (1): CLS 0.00. At the high end (>p98): CLS 0.02. computed

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
4

Why this matters for the Core Web Vitals, and where to start fixing it

Third-party domains are a common Core Web Vitals issue. First of all, each third-party domain needs a new connection. That means time is lost on a DNS lookup, a TCP handshake and a TLS negotiation. If you had served those resources from your main domain, the browser could have re-used the connection that is already open (that is why you want HTTP/3: one fast, re-usable connection for everything you control). When that domain serves a font or a stylesheet, the browser cannot render before the connection is ready. The connection setup delays the LCP.

Also, third-party resources are usually out of your control. They can become a SPOF (single point of failure) when their server is slow or down. They can also change in size or behaviour without your knowledge, and your Core Web Vitals change with them. Self-hosting fixes both problems at once. Preconnect only hides part of the connection cost.

How do third-party domains affect the Core Web Vitals?

Third-party domains correlate with the LCP. With a single third-party domain, 88% of sites pass the LCP. Among the sites with the most third parties, 80% do. The decline is gradual. There is no point where sites suddenly start failing.

The effect is bigger on CLS. With a single third-party domain, 94% of sites pass it. Among the sites with the most third parties, 81% do. Third parties inject ads, embeds and consent banners, and injected content moves the layout after the page looks done.

Go fix it Self-host Google Fonts → The case for limiting analytics and tracking scripts → Guide to resource prioritization →
Related signals Responsive image markup → Stylesheet loading mix → Image format mix → Images per page → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured