The State of Web Vitals

Script origin (1P/3P)

First-party vs third-party scripts - counts and bytes.

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

At a glance the headline numbers for Script origin (1P/3P)

First-party vs third-party scripts - counts and bytes.

2
Categories
In the distribution
78.8%
Fleet share
Top: first_party
97.4%
Sites with any
Of first_party

21.2% of scripts come from third parties.

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

The script origin (1P/3P) mix who uses what, and how stable each group is

Median CLS (sites using feature)
0
0.10
0.20
0.30
0.40
0.50
First party0.0079% of sites
Third party0.0021% of sites
VariantShare of requestsMedian
First party
79%
0.00
Third party
21%
0.00

Script origin (1P/3P). On the fleet: 78.8% first party, 21.2% third party. 97.4% of sites use at least one first_party.

By count first party leads (78.8%); by bytes it is third party (56.1%). computed

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
3

Passing CLS per bucket every category and count level at once - color is the pass rate

1
2
3
4
5
6
7
8
9
10
11
First party 78.8%
87
88
87
89
91
90
89
88
90
87
75
Third party 21.2%
91
90
87
89
89
88
86
85
88
89
84
← few of this category on the pagemany →
60%95%+ of sites passing CLS Faded cells: under 100 sites

Each row is a category, each column its own count bucket (few on the left, many on the right); the cell is the share of those sites passing CLS.

First party swings the hardest: 87% of sites pass CLS with few, 75% with many. computed

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

Few vs many - does quantity cost CLS? the pass rate with few vs many of each category

60%70%80%90%100% few → many
First party 78.8% 87% → 75%
Third party 21.2% 91% → 84%
% of sites passing CLS · hollow ring = pages with few, solid dot = pages with many

Per category: the pass rate among pages with FEW of it (hollow ring) against pages with MANY (solid dot), worst trend first. Thin buckets are excluded from the endpoints.

More First party costs the most: the CLS pass rate falls from 87% with few to 75% with many. computed

The State of Web Vitals · Q1 2026 · 94,910 sites · phone field datacorewebvitals.io/state-of-cwv
5

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

First-party script is in your bundle, your build, your deploy. Third-party script arrives from someone else's server at whatever size and shape it has today. Both run on the same main thread. Only one of them is yours to fix.

A high third-party share is a ceiling on your INP work: optimize your own code all you want, the tags still run between your visitor's clicks. Past that ceiling the fix list changes. Fewer vendors, deferred loading, facades instead of always-on embeds.

How does this affect the Core Web Vitals?

The choice barely moves the INP: 93% pass at best, 92% at worst. This signal does not separate passing sites from failing ones.

Go fix it The case for limiting analytics and tracking scripts → Defer scripts until needed → Chat widgets with perfect Core Web Vitals →
Related signals Script initiator → Image dimensions set → Scripts per page → Stylesheets per page → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured