The State of Web Vitals

Iframe loading

Iframe loading attributes: lazy vs default.

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

At a glance the headline numbers for Iframe loading

Iframe loading attributes: lazy vs default.

2
Categories
In the distribution
93.9%
Fleet share
Top: default
40.5%
Sites with any
Of default

6.1% of iframes are lazy-loaded.

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

The iframe loading 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
Default0.0194% of sites
Lazy0.006% of sites
VariantShare of sitesMedian
Default
94%
0.01
Lazy
6%
0.00

Iframe loading. On the fleet: 93.9% default, 6.1% lazy. 40.5% of sites use at least one default.

Lowest-share bucket: CLS 0.00. Highest-share bucket: CLS 0.01. r = +0.35.

The State of Web Vitals · Q1 2026 · 94,910 sites · all devices 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
Default 93.9%
90
86
86
84
83
82
82
79
74
Lazy 6.1%
88
86
85
83
82
83
← 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.

Default swings the hardest: 90% of sites pass CLS with few, 74% with many. computed

The State of Web Vitals · Q1 2026 · 94,910 sites · all devices 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
Default 93.9% 90% → 74%
Lazy 6.1% 88% → 83%
% 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 Default costs the most: the CLS pass rate falls from 90% with few to 74% with many. computed

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

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

An iframe is a whole page inside your page: its own HTML, scripts and resources. An embed below the fold that loads eagerly spends bandwidth and CPU on something the visitor may never scroll to, and its work competes with your page at the busiest moment of the load.

loading=lazy on iframes defers all of that until the visitor approaches. For YouTube embeds and maps the better pattern is a facade: a static preview that becomes the real embed on click. The page pays for the embed only when someone wants it.

How does this affect the Core Web Vitals?

Of the 2 categories, Lazy separates passing sites from failing sites the most. Where Lazy is rare: 83% pass the LCP. Where it is common: 71%.

Go fix it Perfect YouTube Core Web Vitals → Google Maps with 100 percent PageSpeed → Speed up a Calendly integration →
Related signals Image format mix → Fonts per page → Font source → Script loading mix → Chrome field data from 94,910 sites, representing millions of real page loads · How we measured