94% of e-commerce sites have a JavaScript problem
According to the Noibu 2025 study, 94% of e-commerce sites have at least 5 unresolved JavaScript errors in production at any given time. These are errors users feel, beyond console warnings: forms that won't submit, carousels that block scrolling, buttons that stop responding.
The Contentsquare 2026 Digital Experience Benchmark backs this up: JavaScript errors account for 17.8% of all frustrations detected on e-commerce sites. They are the second biggest source of frustration after load times.
Worse, only 10% of users who hit a bug bother to report it. The other 90% close the tab and go to a competitor.
The gap between technical monitoring and business impact
Tech teams have tools to track JavaScript errors: Sentry, Bugsnag, LogRocket. These tools do their job well: capturing stack traces, pinpointing the source file, measuring frequency.
But they don't answer the CMO's question: "How much is this costing us?"
A JavaScript error that hits 0.3% of sessions on the FAQ page doesn't have the same impact as an error that hits 0.3% of sessions at checkout. Sentry treats them the same way. Your P&L doesn't.
The three families of JS errors that cost money
Three categories of JavaScript errors have a direct, measurable financial impact:
1. Errors that break conversion pixels
A JavaScript conflict can stop the Meta, Google Ads or TikTok pixel from firing. The tag is in GTM, the container loads, but the purchase event is never sent.
Impact: bidding algorithms lose their conversion signal. ROAS collapses artificially. The CMO cuts budget on a channel that is actually converting.
2. Errors that block the purchase
A third-party script that clashes with the credit card form. A React component that crashes on submit. A TypeError: Cannot read property of undefined error that prevents cart validation.
Impact: traffic comes in, users add to cart, but checkout is blocked. Revenue drops to zero while paid campaigns keep running.
3. Errors that degrade performance
An unoptimized script that blocks the main thread for 800 ms. An event listener that triggers a full page re-render. An infinite loop in a third-party component.
Impact: LCP degrades, bounce rate rises, Core Web Vitals turn red. Google demotes the pages in Shopping results.
The real cost
For an e-commerce site with €500,000 in monthly revenue and a €30,000 paid budget, here is what undetected JavaScript errors cost:
| JS error type | Business consequence | Typical frequency | Estimated monthly cost | Korvus alert |
|---|---|---|---|---|
| Conflict with the Meta pixel | Dead pixel, ROAS at 0 | 1-2 times/month | €3,000 - €8,000 | pixel_dead |
| Script blocking checkout | Zero purchases, normal traffic | 2-4 times/month | €5,000 - €15,000 | checkout_zero |
| Component degrading LCP | Rising bounces on paid traffic | Ongoing if undetected | €2,000 - €5,000 | perf_drop |
| Error on a sponsored product page | Invisible CTA, add-to-cart impossible | Variable | €1,000 - €3,000 | sponsored_oos |
| Corrupted dataLayer | Wrong conversion values | 1-2 times/month | €2,000 - €6,000 | checkout_zero |
Estimated total: 5 to 10% of revenue is silently affected by JavaScript errors in production. On €500,000/month, that's €25,000 to €50,000 in lost revenue.
Why Sentry isn't enough
Sentry is an excellent debugging tool. But for a CMO, it has three structural limits:
1. No financial prioritization. Sentry ranks errors by frequency and technical severity. It doesn't know that a rare error on the checkout is worth 100 times more than a frequent error on the "About" page.
2. Too much noise. An average e-commerce site generates hundreds of JavaScript errors a day: browser extensions, bots, third-party scripts. The tech team ends up ignoring the alerts.
3. No link to paid traffic. Sentry doesn't distinguish an organic visitor from a visitor who cost €1.20 in CPC. The error carries the same "weight" in both cases. Your budget doesn't see it that way.
The Korvus approach: watch the consequences, not the causes
Korvus doesn't replace Sentry. It monitors the financial consequences of JavaScript errors rather than the errors themselves.
The logic is flipped:
- Sentry says: "TypeError at line 847 of checkout.bundle.js, 23 occurrences in 1 hour"
- Korvus says: "No purchases for 18 minutes despite 280 active sessions. Estimated loss: €2,100"
The tech team uses Sentry to find the cause. The CMO uses Korvus to know that something is costing money, and how much. The two tools complement each other, but only one of them triggers action on the business side.
Warning signs to watch
Even without a dedicated tool, some signals in your existing data should raise a flag:
- A widening gap between sessions and transactions: if the sessions-to-purchases ratio drops with no marketing reason, a bug is probably blocking the funnel
- A spike in exit pages on checkout: GA4 shows exit pages, and a sudden spike on
/checkoutor/paymentis a strong signal - ROAS crashing on a single channel: if Meta ROAS drops from 4 to 0.5 in 24 hours with no campaign change, the pixel is probably dead
- GA4 conversions diverging from your backend: if GA4 shows 50% fewer conversions than your database, a script is stopping events from going out
Key takeaways
- 94% of e-commerce sites have unresolved JavaScript errors in production
- These errors cost 5 to 10% of revenue, silently, with no alert
- Sentry sees stack traces but not the financial impact: errors are ranked by frequency, not by cost
- Korvus watches the financial consequences of JS errors: dead pixel, blocked checkout, degraded performance
- The most effective approach: Sentry for technical diagnosis, Korvus for business prioritization