The State of Web Vitals

Script initiator

What injected each script: the HTML parser, another script, or inline markup.

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 initiator

What injected each script: the HTML parser, another script, or inline markup.

4
Categories
In the distribution
40.6%
Fleet share
Top: inline
94.1%
Sites with any
Of inline

18.3% of scripts are injected by other scripts.

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

The script initiator mix who uses what, and how fast each group loads

Median INP (sites using feature)
0
100ms
200ms
300ms
400ms
500ms
Inline98ms41% of sites
Parser98ms40% of sites
Script102ms18% of sites
Other104ms1% of sites
VariantShare of requestsMedian
Inline
41%
98ms
Parser
40%
98ms
Script
18%
102ms
Other
1%
104ms

Script initiator. On the fleet: 40.6% inline, 40.2% parser, 18.3% script. 94.1% of sites use at least one inline.

By count inline leads (40.6%); by bytes it is parser (49.5%). computed

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

Passing INP 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
Inline 40.6%
87
91
93
92
93
93
95
94
94
93
83
Parser 40.2%
89
90
91
92
95
95
94
94
94
88
Script 18.3%
95
94
95
93
92
92
91
92
88
84
86
Other 1%
89
91
87
90
93
94
93
90
← few of this category on the pagemany →
60%95%+ of sites passing INP 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 INP.

Script swings the hardest: 95% of sites pass INP with few, 86% 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 INP? the pass rate with few vs many of each category

60%70%80%90%100% few → many
Script 18.3% 95% → 86%
Inline 40.6% 87% → 83%
Parser 40.2% 89% → 88%
Other 1% 89% → 90%
% of sites passing INP · 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 Script costs the most: the INP pass rate falls from 95% with few to 86% 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

How a script got onto the page predicts when it runs. Parser-discovered scripts are visible to the preload scanner from the first bytes of HTML. Script-injected scripts are invisible until their parent downloads, parses and runs. That is a chain, and every link adds a network round trip.

Tag managers build these chains by design: the manager loads, then injects tags, which inject more tags. Each hop lands late and competes with your page. Flattening one chain often helps more than minifying everything.

How does this affect the Core Web Vitals?

The choice barely moves the INP: 93% pass at best, 90% at worst. This signal does not separate passing sites from failing ones.

Go fix it Avoid chaining critical requests → The case for limiting analytics and tracking scripts → Head vs footer JavaScript →
Related signals Uses @import → Iframe dimensions set → Responsive image markup → Third-party share → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured