Shaping the Future of Payments in the Browser

Part 1: Setting up Our Experiment with the Payment Request API

By Anna Gyergyai and Krystian Czesak

At Shopify, the leading multi-channel commerce platform that powers over 600,000 businesses in approximately 175 countries, we aim at making commerce better for everyone. This sometimes means investing in new technologies and giving back what we learned to the community, especially if it’s a technology we think will drastically change the status quo. To that end, we joined the World Wide Web Consortium's (W3C) Web Payments Working Group in 2016 to take part in shaping the future of native browser payments. Since then, we’ve engaged in opinionated discussions and participated in a few hack-a-thons (Interledger Payment App as an example) as a result of this collaborative and innovative working environment.

The W3C aims to develop protocols and guidelines that ensure the long-term growth of the Web. The Web Payments Working Group’s goal is to make payments easier and more secure on the Web. The first specification they introduced was Payment Request: a javascript API that replaces traditional checkout forms and vastly simplifies the checkout experience for users. The first iteration of this specification was recently finalized and integrated into a few browsers, most notably Chrome.

Despite being in Candidate Recommendation, Payment Request’s adoption by platforms and developers alike is still in the early stages. We found this to be a perfect opportunity to test it out and explore this new technology. The benefits of such an initiative are threefold. We gather data that helps the W3C and browser vendors grow this technology, continue to contribute to the working group, and encourage participation through further experimentation.

Defining the Project

To present detailed findings to the community, we first needed a properly formulated hypothesis. We wanted to have at least one qualitative and one quantitative success metric, and we came up with the following:

We believe that Payment Request is market ready for all users of our platform (of currently supported browsers). We’ll know this to be true when we see that the checkout completion rate for select merchants remains unchanged or gets better, and the purchase experience is better and faster.

This was our main driving success metric. We define checkout completion rate (CCR) as the number of people that completed a purchase vs the total number of people that demonstrated an intent to purchase. An intent to purchase is indicated by buyers who clicked the “checkout” button on the cart page. In addition, we monitored time to completion of the purchase and drop-off rates.

For our qualitative metric, we spent time comparing Payment Request’s checkout experience with Shopify’s existing purchase experience. This metric was mostly driven by user experience research and was less of a data-driven comparison. We’ll cover this in a follow-up post.

We set off to launch an A/B experiment with a group of select merchants that showed interest in the potential this technology had to offer. We built this experiment outside of our core platform because a few key benefits allowed us to:

  • Iterate fast and in isolation
  • Leverage our own platform’s existing APIs
  • Release the app to our app marketplace for everyone to use, if valuable

Payment Request API Terminology

The Payment Request API has interesting value propositions: it surfaces more than one payment method, it’s agnostic of the payment method used, and it can indicate back upstream if the buyer is able to proceed with a purchase or not. This last feature is referenced as the canMakePayment() method call, which returns a boolean value indicating that the browser supports any of the desired payment methods indicated by the merchant.

Most browsers that implement Payment Request allow processing credit card payments through it (this payment method is referenced as basic-card in the specification). At the time of writing, basic-card was the only payment method widely implemented in browsers, and as a result, we ran our experiment with credit card transactions in mind only.

In the case of basic-card, canMakePayment() would return true if the end user already had a credit card provisioned. As an example on Chrome, the method returning true would mean that the user had already a credit card on file in their browser either through one of Chrome’s services, autofill or from having already gone once through the Payment Request experience.

Payment Request demo on Chrome Android
Payment Request demo on Chrome Android

Finally, the UI presented to the buyer during their purchase journey through Payment Request is called the payment sheet. Its implementation depends on the browser vendor, which means that the experience might differ from one browser to another. As seen in the demo above, it usually contains the buyer’s contact information, shipping address and payment method. Once the shipping address is selected, the buyer is allowed to select their shipping method (if applicable).

Defining our A/B Experiment

Our A/B experiment ran on select merchants and tested buyer behaviour. The conditions of the experiment are as follows:

Merchant Qualification

Merchant Qualification

Since most Payment Request implementations in browsers only support the basic-card payment method, we were limited to merchants who accept direct credit card payments as their primary method of payment. With this limitation, one of the primary merchant qualifications was the use of a credit card based payment processor.

Audience Eligibility

Our experiment audience is buyers. A buyer is eligible to be part of the experiment if their browser supports Payment Request. At the time of writing, Payment Request is available with the latest Chrome (on all devices), Microsoft Edge on desktop and Samsung Browser (available on Samsung mobile devices). We were only able to gather experiment data on Chrome. We experienced minimal browser traffic through Samsung Browser, and Microsoft Edge's Payment Request implementation only supports North American credit cards.

Experiment Segmentation

From the qualified buyers, when they clicked the “checkout” button on the cart page, 50% of them are placed in a control group and the other 50% in an experiment group. The control group are buyers that won’t see the payment sheet and continue through our regular checkout. The buyers that go through the Payment Request purchase experience and see the payment sheet are the experiment group.

Payment Request Platform Integration

In order to build our experiment in an isolated manner, we leveraged our current app ecosystem. The experiment ran in a simple ruby app that uses our existing rails engine for Shopify Apps. We used our existing infrastructure to quickly deploy to Google Cloud (more on our move to the cloud here). In conjunction with our existing ShipIt deployment tool, we were able to setup a pipeline in a matter of minutes, making deployment a breeze.

After setting up our continuous delivery, we then shifted our focus towards the app lifecycle, which can be better explained in 2 phases: merchant facing app installation and the buyer’s storefront experience.

App Installation

The installation process is pretty straightforward: once the merchant gives permission to run the experiment on their storefront, we then install our app in their backend. Upon installation, our app injects a script tag on the merchant’s storefront. This javascript file contains our experiment logic and would run for every buyer visiting that merchant’s shop.

Storefront Experience

The buyer’s storefront experience is split into two processes: binding the experiment logic and surfacing the right purchase experience.

Storefront Experience - Binding the Experiment LogicBinding the experiment logic

Every time a buyer visits the cart page, our front-end logic first determines if the user is eligible for our experiment. If so, the javascript code pings our app backend, which in turn gathers the shop’s information through our REST Admin API. This ping determines if the shop still has a credit card based processor and if the merchant supports discount codes or gift cards. This information determines the shop’s eligibility for the experiment and displays the proper alternative flow if gift cards or discount codes are accepted. When both the buyer and the merchant are eligible for the experiment, we override the “checkout” button on the cart page. We usually discourage this practice, as it can cause the checkout experience to be adversely affected. For our purposes, we allowed it for the duration of the experiment only.

Surfacing the Purchase ExperienceSurfacing the purchase experience

Upon clicking the Checkout button, buyers in our control group would get redirected to Shopify’s existing web checkout. Buyers in our experiment group would enter the Payment Request experimental flow via the Payment sheet, and the javascript would interact with Shopify’s Checkout API to complete a payment.

Alternative Payment Flows

Since the majority of merchants on the Shopify platform accept discount codes and gift cards as part of their purchase flow, it was important to not negatively impact the merchants’ business during this experiment due to the Payment Request API not supporting discount code entry.

Shopify only supports this feature on the regular checkout flow, and implementing this feature on the cart page prior to checkout would involve a non-trivial effort. Therefore, we needed to provide an ability for buyers to opt out of the experiment if they wanted to provide a discount code. We included a link under the checkout button that read: “Discount or gift card?”. Clicking this link would redirect the buyer to our normal checkout flow, where they could use those items, and they would never see the payment sheet.

Finally, if the buyer cancelled the payment sheet purchase flow or an exception occurred, we’d show a link under the checkout button that reads: “Continue with regular checkout”.

What’s Next

The Payment Request API can provide a better purchase experience by eliminating checkout forms. Shopify is extremely interested in this technology and ran an experiment to see if Payment Request was market ready. Now that we've talked about how the experiment was set up, we’re excited to share experiment data points and lessons in the second part of Shaping the Future of Payments in the Browser. It will include breakdowns in time to completion times, user flow learnings in buyer interactions and Payment Request’s overall effect on the purchase experience (both quantitative and qualitative).

Part 2: The Results of Our Experiment with Payment Request API

In Part 1, we dove into how we ran an experiment in order to test the readiness of Payment Request. The goal was to invest in this new technology and share what we learned back to the W3C and browser vendors, in order to improve web payments as a whole. Regardless of the conclusion of the experiment on our platform, we continue to invest in the current and future web payments specifications.

As a reminder, our hypothesis was as follows:

We believe that Payment Request is market ready for all users on our platform (of currently supported browsers). We’ll know this to be true when we see that the checkout completion rate for select merchants remains unchanged or gets better, and the purchase experience is better and faster.

We define checkout completion rate (CCR) as the number of people that completed a purchase vs the total number of people that demonstrated an intent to purchase. An intent to purchase is indicated by buyers who clicked the “checkout” button on the cart page.

In this post, we investigate and analyze the data gathered during the experiment, including checkout completion rates, checkout completion times, and drop-off rates. This data provides insight on future Payment Request features, UX guidelines, and buyer behaviour.

Data Insights

We ran our experiment for over 2 months with 30 merchants participating. At its peak, there were around 15,000 payment sheet opens per week. The sample size allowed us to have high confidence in our data and our standard error is ±1%.

Time to Completion

Time to Completion

Form Factor


10th percentile Median time 90th percentile
Desktop true 0:54 2:16 6:23
Desktop false 1:33 3:13 7:57
Mobile true 0:56 2:35 6:29
Mobile false 1:35 3:22 8:08

Time to completion by device form factor

The time to completion is defined as the time between when the buyer clicks the “checkout” button until their purchase is completed (i.e. they’re on the order status page). The value of canMakePayment() determines if the buyer has a credit card provisioned or not. As an example on Chrome, the method returning true would mean that the buyer had already a credit card on file in their browser; either through one of Chrome’s services, autofill, or from having already gone once through the Payment Request experience.

The median time for buyers with canMakePayment() = false is 3:17 whereas the median time for buyers with canMakePayment() = true is 2:25. This is promising, as both medians are faster than our standard checkout. We can also take a look at the 10th percentile with canMakePayment() = true and see that the checkout completion times are under a minute.

Checkout Completion Rates

As mentioned previously, we define checkout completion rate (CCR) as the number of people that completed a purchase vs the total number of people that demonstrated an intent to purchase. Comparing the control group to the experiment group, we saw a average 7% drop of CCR (with a standard error of ±1%), regardless of canMakePayment().

It is important to put this 7% into perspective. The Payment Request API is still in its infancy: the purchase experience it’s leveraging (through the payment sheet) is something buyers are still getting accustomed to. A CCR drop in the context of our experiment is to be expected, as buyers on our platform are familiar with a very specific and tailored process.

Our experiment did not adversely affect the merchants overall CCR, being that it only ran on a very small subset of buyer traffic. Looking at all eligible merchants, the experiment represented roughly 5% of their traffic, as seen in the following graph:

Overall experiment traffic relative to normal site traffic

We started by slowly ramping up the experiment to select eligible merchants. This explains the low traffic percentage at the beginning of the graph above.

User Flow Analysis

The graph below documents the buyer’s journey through the payment sheet by listing all possible events, in the order they occurred during the purchase session. An event is a user interaction like the user clicking the checkout button or selecting a shipping method. All the possible events can be seen on the right side of the graph below. Not shown on the graph, is that 10% of buyers prefer clicking the provided “Discount or gift card?” link rather than on the “checkout” button, before entering into the experiment.

The ideal user flow for the experiment is:

  1. The buyer clicks the “checkout” button
  2. The payment sheet opens
  3. The buyer selects a shipping address
  4. The buyer selects a shipping method
  5. The buyer clicks “pay”
  6. The payment is successful

The number at the top of the bars indicate the percentage of events that occurred at that step relative to step 1. For example, by step 6, a total of 43% of events were emitted compared to step 1.

Payment sheet event breakdown by order of occurrence
Payment sheet event breakdown by order of occurrence

Here are some ways the user flows break down:

  • [Step #1 to Step #2] Not all buyers who click the button will see the payment sheet. This is due to the various conflicting Javascript on the merchant’s storefront, leading to exceptions
  • [Step #3] Upon seeing the payment sheet, 60% of buyers will drop out without interacting with their shipping contact information or provided shipping methods
  • [Step #4] Once they exited the sheet, 35% of buyers prefer clicking on one of the other links provided. 84% of these will click the “Discount or gift card?” link while the rest will click on the “Continue with regular checkout” link. A small percentage of buyers will retry the payment sheet.
  • [Step #5] 32% of buyers will initiate a payment in the payment sheet by clicking the “Pay” call to action
  • [Step #6] At this point, 28% of buyers are able to complete their checkout. The rest will have to retry a payment because of a processing error such as an invalid credit card, insufficient funds, etc...

Of the buyers that don’t go to through the payment sheet, only 30% of them will retry one or two times to go through Payment Request again and 7% of buyers will retry two or more times.

Furthermore, we don't know why 60% of buyers drop out of the payment sheet, as the Payment Request API doesn’t provide event listeners on all sheet interactions. However, we think that the payment sheet being fairly foreign to buyers might be part of the cause. This 60% drop out rate certainly accounts for the 7% CCR drop we mentioned earlier. This is not to say that the purchase experience is subpar; rather, that it will take time for buyers to get accustomed to. As this new specification gains traction and adoption broadens, we think that the number of buyers that drop out will significantly decrease. Our merchant feedback seems to support our hypothesis:

“I found the pop-up really surprising and confusing because it doesn't go with the rest of our website.”

“[...] it comes up when you are still on the cart page even though you expect to be taken to checkout. It's just not what you are used to seeing as a standard checkout process [...]”

“My initial thoughts on it is that the UI/UX is harshly different than the rest of our site and shopify [...]”

Merchants were definitively apprehensive of Payment Request, but were quite excited by the prospect of a streamlined purchase experience that could leverage the buyers information securely stored in the browser. This is best reflected in the nuanced feedback we received after our experiment ended:

"I just wanted to check in and see if there was any update with this. We’d really love to try out the new checkout again."

“[...] I love the test, it’s just a pretty drastic change from what online shoppers are used to in terms of checkout process.”

Finally, to better understand merchant feedback, we performed user experience research on the different payment sheet UIs implemented by browser vendors. We’ll share specific research insights with the concerned browser vendors, but the lessons listed below can be applied to all payment sheets and are recurring throughout implementations.

We found that in order to create more familiarity with the buyer as they navigate from the storefront to the payment sheet, it’s useful to surface the merchant’s name or logo as part of it. Furthermore, it’s important to keep “call to actions” with negative connotations (i.e. cancel or abort) in the same area in every payment sheet screen. This helps to set the proper expectations for the buyer. An example is having the “Pay” call to action in the bottom right of the very first screen, then having a “Cancel” call to action in the bottom right of the next screen.

As for the user experience, it’s preferred not to surface grayed out fields unless they are preselected. An example is surfacing a grayed out shipping address to the buyer on the very first screen of the payment sheet, without it being preselected. The buyer might think that they don’t have to select a shipping address as it’s already presented to them. This leads to confusion for the buyer and relates well to merchant feedback we’ve received:

“When this pops up, it's really unclear how to proceed so much so that it was jarring to see "Pay" as the CTA button [...]”

Finally, to prevent unnecessary back and forth between screens, surface validation errors as soon as possible in the flow (ideally in the form, near the fields).

Experiment Conclusion

Reiterating our initial hypothesis:

We believe that Payment Request is market ready for all users on our platform (of currently supported browsers). We will know this to be true when we see that the checkout completion rate for select merchants remains unchanged or gets better, and the purchase experience is better and faster.

Event though merchants were interested in the prospect of Payment Request, we don’t believe that Payment Request is a good fit for them yet. We pride ourselves on offering a highly optimized checkout across all browsers. We constantly tweak it by running extensive UX research, testing it against multiple devices, and regularly offering new features and interesting value propositions for merchants and buyers alike. These include Google Autocomplete for Shopify, Shopify Pay or Dynamic Checkout, which allow us to streamline the purchase experience.

As buyer recognition of the feature grows and browsers tweak their UI to improve the payment sheet, we believe that the aforementioned 7% Checkout Conversion Rate drop and the 60% drop of buyers at the payment sheet will greatly diminish. Paired with the very promising time to completion medians, we are excited to see how the specification will grow in the upcoming months.

What’s next

Payment Request has a bright future ahead of it as both the W3C and browser vendors show interest in pushing this technology forward. The next major milestone for Payment Request is to accept third party payment methods through the new Payment Handler API, which will definitely help adoption of this technology. It was, up until recently, only available behind a feature flag in Chrome but Google has officially rolled it out as part of v68. We’ve already started experimenting with this next specification and are quite excited by its possibilities. You can find several demos we recorded for the W3C here: Shopify Web Payments Demos. We chose Affirm and iDeal as payment methods for the exploration, and the results are promising.

Shopify’s excited to be part the Web Payments Working Group and thrilled to hear your comments. We invite you to explore the specification by implementing it on your own website. Then join the discussion over at the Web Payments Slack group or over at W3C’s wiki page, where you’ll find resources to comment, discuss and help us in developing this new standard.

We do believe Payment Request has great potential and will shift the status quo in web payments. We’re excited to see the upcoming changes to Payment Request. Shopify is very keen on the technology and remains active in W3C discussions regarding web payments.