Some changes are uncertain: nobody knows whether a new layout will help. Others aren’t: a button that doesn’t work on some phones is costing you orders, and nobody needs a test to know it. Treating the second kind like the first is one of the most expensive habits in conversion work.

What goes straight on the fix list

• Errors and bugs. In Baymard Institute’s survey of US shoppers, 17% said they’d abandoned an order because of website errors or crashes Reported. Check the checkout on every major phone and browser you get traffic from, every month.
• Slowness. Google’s Core Web Vitals give the thresholds for a good experience, measured on 75% of page loads: the main content loads within 2.5 seconds, the page responds to a tap within 200 milliseconds, and the layout doesn’t jump around, a shift score of 0.1 or less Published. Shopify’s own help pages name installed apps as one of the biggest factors in store speed, and note that uninstalling an app doesn’t automatically remove its code from your theme Published.
• Missing answers. Anything your five sessions or your survey show people looking for and not finding: the delivery date, the total cost, the returns policy, the sizing. Chapter 9.
• Unnecessary steps. Baymard finds the average US checkout shows 23.48 form elements, where 12 to 14 would do, and that the average large site could raise its conversion rate by 35.26% through better checkout design Reported. That’s an estimate from their benchmarking, not an experiment, but the direction of every item on it is clear: fewer fields, guest checkout, express wallets.

Speed, with the evidence sorted

Speed is where the evidence is most often overstated, so sort it. The strongest example is Vodafone’s: a true A/B test in Italy, with half the traffic sent to an optimized landing page. Its main content loaded 31% sooner, by the measure Google calls Largest Contentful Paint, and sales rose 8% Reported. The widely quoted Deloitte study for Google, which found that a 0.1-second improvement went with 8.4% more retail conversions, is observational: it watched speed vary naturally across 37 brands Reported. And the old line that 53% of mobile visits are abandoned after three seconds comes from 2016 Google data with thin methods; it’s too dated and loosely sourced to plan around. Speed matters. Measure your own before and after.

If five of five people trip on it, fix it. Save your traffic for questions you can’t answer by watching.

When a fix should still be tested

A few “obvious” fixes have real downsides and deserve a test or a holdout: anything that changes price or what the customer pays for shipping, anything that removes information some shoppers rely on, and anything that trades conversion for margin. Everything else, fix.

And fix before you test anything else on the same page. A test run on top of a broken baseline credits the new version with the repair. Log each fix with its date, so the before-and-after in chapter 6 has something to read.

Do this

• Make the fix list from your funnel, your five sessions and a speed check of your top three pages on a phone. Ship the top three fixes this sprint, each logged with the date it went live.