Wix font-display and the Core Web Vitals

Here, a site counts under every font-display value present in its @font-face rules. Sites with at least one matching rule have a good LCP: swap at 94%, auto at 88%. Why does swap (94%) sit right next to auto (88%)? Three in four sites that load Google Fonts with swap also load icon or theme fonts with block or auto. Those multi-font pages count under both values.

Here, a site counts under every font-display value present in its @font-face rules. Sites with at least one matching rule have a good CLS: auto at 98%, swap at 98%. Why does swap (98%) sit right next to auto (98%)? Three in four sites that load Google Fonts with swap also load icon or theme fonts with block or auto. Those multi-font pages count under both values.

Across 5,619 Wix sites that declare web fonts, swap accounts for 98.6% of all @font-face rules, auto for 1.1%, block for 0.3%, fallback for , and optional for . At the site level, 15.1% of sites mix swap with blocking rules on the same page, 0.1% use only blocking rules (auto, block, or fallback), and 84.8% use swap or optional on every font rule.

When each site is counted once by its full rule mix, sites that keep every font on swap or optional have a good LCP on 95% of sites, against 100% for blocking-only sites and 88% for mixed sites. Mixed sites load a median of 6 font files across 56 @font-face rules (usually Google Fonts plus Font Awesome or theme icon fonts). Pure swap sites load a median of 5 font files across 41 rules.

When each site is counted once by its full rule mix, sites that keep every font on swap or optional have a good CLS on 98% of sites, against 100% for blocking-only sites and 97% for mixed sites. Mixed sites load a median of 6 font files across 56 @font-face rules (usually Google Fonts plus Font Awesome or theme icon fonts). Pure swap sites load a median of 5 font files across 41 rules.

Comparing sites that load the same number of font files separates font-display from font count. With 1 to 2 font files, sites on pure swap have a good LCP on 96% of sites, against 80% for sites with any block rule. On pages loading 8 or more font files, pure swap reaches 94% against 79% for sites with block.

Comparing sites that load the same number of font files separates font-display from font count. With 1 to 2 font files, sites on pure swap have a good CLS on 98% of sites, against 80% for sites with any block rule. On pages loading 8 or more font files, pure swap reaches 98% against 89% for sites with block. At every font count, pure swap matches or beats block on field CLS.

On React, 99% of declared @font-face rules use font-display: swap, 1% use auto, and 0% use block. 94% of React sites have a good LCP.

On React, 99% of declared @font-face rules use font-display: swap, 1% use auto, and 0% use block. 98% of React sites have a good CLS.

Framework@font-face rules on its sitesGood LCP

Wix sites with font-display 5,619 sitesswap 99%94%

React 5,618 sitesswap 99%94%

swap auto (browser default) block fallback optional

Does the framework explain the font-display gap?

On React, 95% of sites that keep every font on swap or optional have a good LCP, compared with 100% for blocking-only sites and 88% for React sites that mix swap with blocking rules. Within React, keeping every font on swap beats mixing rules by 7 percentage points.

On React, 98% of sites that keep every font on swap or optional have a good CLS, compared with 100% for blocking-only sites and 97% for React sites that mix swap with blocking rules. Within React, pure swap and mixed sites have a good CLS about equally often.

How font-display affects LCP and CLS during page load

When text is the LCP element, font-display: block and font-display: auto hide it for up to 3 seconds while the font file downloads. If the font arrives late, that wait delays LCP directly. With font-display: swap, the browser paints the fallback system font right away so LCP is recorded on first render, then swaps in the web font once it downloads. Swapping an unadjusted fallback font can shift text lines. Even so, pure swap sites match or beat blocking sites on field CLS at every font count (98% good CLS).