The State of Web Vitals

Stylesheet origin (1P/3P)

First-party vs third-party stylesheets - 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 Stylesheet origin (1P/3P)

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

2
Categories
In the distribution
92.2%
Fleet share
Top: first_party
97.9%
Sites with any
Of first_party

7.8% of stylesheets load from servers their site does not control.

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

The stylesheet 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 party0.0092% of sites
Third party0.008% of sites
VariantShare of requestsMedian
First party
92%
0.00
Third party
8%
0.00

Stylesheet origin (1P/3P). On the fleet: 92.2% first party, 7.8% third party. 97.9% of sites use at least one first_party.

First party leads by count (92.2%) and by bytes (92.2%). 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
First party 92.2%
92
90
90
89
88
89
89
88
86
85
Third party 7.8%
89
88
87
86
87
88
87
87
88
79
← 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.

Third party swings the hardest: 89% of sites pass CLS with few, 79% 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
Third party 7.8% 89% → 79%
First party 92.2% 92% → 85%
% 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 Third party costs the most: the CLS pass rate falls from 89% with few to 79% 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

A third-party stylesheet is render-blocking content on someone else's server. Your first paint waits on their TTFB and their availability. Font CSS is the classic case, widget styles the second.

CSS files are small and change rarely, so there is no good reason not to self-host them. This is the SPOF (single point of failure) case with the highest stakes: when that server is slow, it is not a feature that waits, it is rendering.

How does this affect the Core Web Vitals?

The choice barely moves the LCP: 82% pass at best, 80% at worst. This signal does not separate passing sites from failing ones.

Go fix it Self-host Google Fonts → Eliminate render-blocking resources →
Related signals Bytes by resource type → Image source mix → Stylesheet loading mix → Uses @import → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured