CWV pass rate for stores with and without a pay-later option, by platform
| Platform | Pass with pay-later | Pass without | Median JS with | Median JS without | Stores with (CrUX) | Stores without (CrUX) |
|---|---|---|---|---|---|---|
| Shopify | 60.4% | 57.3% | 3.38 MB | 2.93 MB | 6,850 | 38,407 |
| WooCommerce | 23.8% | 36.2% | 1.61 MB | 0.99 MB | 399 | 20,143 |
| Other store platforms | 35.3% | 41.6% | 1.81 MB | 1.39 MB | 1,353 | 19,135 |
| All stores | 54.7% | 48.0% | 3.05 MB | 1.87 MB | 8,602 | 77,685 |
Source: PageSpeed Matters, HTTP Archive top 1M crawl and CrUX, Sept 2026.
Summary
Buy now, pay later options are now a standard part of online checkout, and the providers compete hard for space on product and cart pages. We wanted two answers: which pay-later tools stores actually install, and whether the extra scripts cost those stores speed.
On adoption, one provider dominates. Shop Pay Installments appears on 27,943 of 40.3 million homepages crawled, against 3,143 for Klarna, 1,881 for Afterpay and 1,583 for Affirm. That is roughly nine times Klarna. On speed, the picture depends on the platform, and the simple headline comparison is misleading.
What we measured
We used two separate samples, and the numbers from each should be read on their own.
Adoption counts cover 40.3 million homepages crawled between January and October 2026. We counted homepages that carry each provider's widget markup or load its scripts.
Speed figures come from the HTTP Archive crawl of the top 1M sites from September 2026, on mobile. We flagged store homepages that load a pay-later integration and joined them to Chrome UX Report (CrUX) field data at the 75th percentile. A store passes Core Web Vitals when loading, responsiveness and visual stability are all good.
Shop Pay Installments leads by a wide margin
Across 40.3 million homepages, Shop Pay Installments is on 27,943. Klarna is on 3,143, Afterpay on 1,881 and Affirm on 1,583. Klarna, Afterpay and Affirm combined reach 6,607 homepages, still less than a quarter of Shop Pay Installments' count.
The lead comes from distribution. Shop Pay Installments is built into Shopify's checkout and can be switched on from the admin, so it reaches stores without a separate app install.
The top 1M crawl gives a different view, because it only covers the most visited sites and detects integrations differently. There, Klarna is detected on 6,564 store homepages, Affirm on 687, SeQura on 554, Sezzle on 510 and Scalapay on 497. Because the two samples are built differently, the counts from one should not be compared directly with the other.
The headline speed gap is platform mix
At first glance, pay-later stores look faster. Top 1M stores with a pay-later integration pass Core Web Vitals 54.7% of the time (8,602 stores with CrUX data), against 48.0% of stores without one (77,685). That is despite loading a median 3.05 MB of JavaScript, against 1.87 MB for stores without pay-later.
The gap is mostly about which platform those stores run on. 77.2% of the 9,255 stores with a pay-later integration run on Shopify, against 47.2% of stores without one. Shopify stores pass Core Web Vitals more often than stores on most other platforms, so a group that is mostly Shopify will look faster whatever widgets it carries. Pay-later tools do not make stores faster.
Platform by platform, the picture changes
Comparing stores on the same platform removes most of that effect. On Shopify, stores with a pay-later option pass 60.4% of the time (6,850 with CrUX data) against 57.3% without (38,407). The gap shrinks to about 3 points, with a median of 3.38 MB of JavaScript against 2.93 MB.
On WooCommerce the pattern reverses. Stores with a pay-later integration pass only 23.8% of the time (399 with CrUX data), against 36.2% without (20,143). Their median LCP is 3,120 ms against 2,675 ms, and they load a median 1.61 MB of JavaScript against 0.99 MB.
On store platforms other than Shopify and WooCommerce, pay-later stores also trail: 35.3% pass (1,353) against 41.6% without (19,135). On Shopify, pay-later stores sit slightly ahead; everywhere else, they sit behind.
Source: PageSpeed Matters. HTTP Archive top 1M crawl, Sept 2026, mobile, CrUX p75.
Correlation only. Pay-later tools do not make stores faster; the overall gap reflects platform mix.
What this means for your store
Offering pay-later can help shoppers who would otherwise leave at the price, but the way it is added matters for speed. On Shopify, the built-in option adds little weight. On WooCommerce and other platforms, pay-later usually arrives as a plugin plus a third-party script and messaging widget on product and cart pages, and those stores pass Core Web Vitals less often.
If you add a pay-later option, load its messaging script only on the pages that show it, defer it until after the main content renders, and reserve space for the widget so it does not shift the layout. Then check your product pages in PageSpeed Insights before and after, so you know what the option costs in speed against what it earns in conversions.
Sources
- PageSpeed Matters analysis of 40.3M homepages crawled January to October 2026
- HTTP Archive crawl of the top 1M sites, September 2026, mobile
- Chrome UX Report (CrUX) documentation, Google: https://developer.chrome.com/docs/crux
Embed this research
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<script>window.addEventListener("message",function(e){if(e&&e.data&&e.data.psmEmbed==="bnpl-market-share"&&e.data.height){var f=document.getElementById("psm-bnpl-market-share");if(f){f.style.height=e.data.height+"px";}}});</script>
<p style="font:14px/1.5 system-ui,sans-serif">Source: <a href="https://www.pagespeedmatters.com/resources/data-studies/bnpl-market-share">BNPL Market Share 2026: Shop Pay Installments 9x Klarna - PageSpeed Matters</a></p>
Frequently asked questions
What is the most popular buy now, pay later option for online stores?
Shop Pay Installments, by a wide margin. Across 40.3 million homepages crawled since January 1, 2026, it appears on 27,943, against 3,143 for Klarna, 1,881 for Afterpay and 1,583 for Affirm.
Do pay-later widgets slow down a store?
It depends on the platform. On Shopify, stores with a pay-later option pass Core Web Vitals 60.4% of the time against 57.3% without. On WooCommerce they pass 23.8% against 36.2%, and on other store platforms 35.3% against 41.6%.
Why do pay-later stores pass Core Web Vitals more often overall?
Platform mix. 77.2% of stores with a pay-later integration run on Shopify, against 47.2% of stores without one, and Shopify stores pass more often in general. Compared platform by platform, the gap shrinks or reverses.
Pay-later messaging can lift conversions, but only if it is added in a way that does not slow down the product page. Need help with this? See our ecommerce CRO agency.