Why Website Updates Break Things (and How to Prevent It)

You asked your developer to update the pricing table. Three days later, a customer emails to say your contact form isn’t working. The two events look unrelated. They almost certainly are related.

This is a regression: a change in one part of a system that breaks something in another. It happens because modern websites are interconnected — shared CSS, shared JavaScript, shared component libraries — and a change to one element can have invisible consequences elsewhere.

Key Findings

• 1 in 4 website updates introduces a secondary problem elsewhere on the site. [Source: Sucuri Website Threat Research Report 2024] Most go undetected for days.
• The three most common regression targets are forms, mobile layouts, and navigation. These elements are most likely to be affected by shared code changes that appear targeted at something else.
• Regression testing is what separates professional maintenance from ad-hoc editing. Testing only the changed element is easy. Testing everything the change may have affected is the work most vendors don’t do.

Why Changes Break Other Things

Modern websites share infrastructure across pages and elements. When you change one piece, others can shift.

CSS changes cascade. A font size adjustment on a headline may shift the spacing of a nearby button. A new color class on a section may inherit globally and apply where it shouldn’t. A z-index change for a modal may cause a form to render underneath an invisible overlay.

JavaScript conflicts. Plugins and apps run scripts that interact with each other. When a third-party script updates, it may conflict with another script already running on the page. A checkout plugin and a live chat plugin that coexisted fine for six months can conflict when either updates.

Template inheritance. Many website platforms use shared templates. A change to the homepage template may affect every page that inherits from it — including pages you didn’t intend to touch.

Plugin and app update side effects. On WordPress and Shopify especially, platform-level updates and app updates can affect custom configurations that have been stable for years.

The Three Most Common Regression Failures

1. Forms stop submitting. A CSS change shifts a button off its click target. A JavaScript conflict prevents the submit handler from firing. A form field validation rule becomes too strict after a plugin update. The form looks fine. It doesn’t work.

2. Mobile layouts break. A responsive layout that works perfectly on desktop collapses on mobile after a change to a shared stylesheet. The tap target for a CTA moves off-screen. Navigation doesn’t open. Most founders don’t catch these because they check on desktop.

3. Navigation and overlays conflict. A z-index change for a promotional banner pushes the navigation menu behind another element. A modal overlay stops responding to the close button. These failures are immediately visible — but usually first spotted by customers.

The Testing Protocol That Prevents Regressions

After every website update, run:

1. Updated section on desktop — correct layout and content?
2. Updated section on mobile (375px, 390px, 414px) — correct layout, no overflow?
3. Surrounding sections on the same page — unaffected?
4. Any page using the same template or shared components
5. All forms on the updated page — test submission end-to-end, verify delivery
6. All primary CTAs — link to the correct destination?
7. Navigation — open, close, all links work?
8. Page load time — not degraded from baseline?

This takes 15–25 minutes per change. It prevents the two-week discovery period where your form has been broken since the last update.

What a Tuesday Engagement Looks Like

Every Tuesday change includes this regression check as a standard deliverable — not a separate request, not an add-on, not an optional extra.

Core Plan — $199/month:

• 10 change requests per month
• 48-hour standard turnaround
• Full regression QA on every change: updated section, adjacent pages, forms, mobile layouts
• Regressions introduced by Tuesday are fixed at no extra charge
• Works on Wix, WordPress, Webflow, and Shopify

Check your regression risk →

Frequently Asked Questions

Why does a text change break a form? Text changes sometimes involve CSS adjustments that affect the form’s layout. More commonly, the same deploy that ships the text change also ships a plugin or script update that was queued alongside it. The text change is visible; the plugin update is not.

How do I know if my website has a regression right now? Submit a test through every contact form. Load your homepage on mobile and check for layout issues. Try clicking every primary CTA and verifying the destination. If any of these fail, you have an active regression.

Who is responsible for fixing regressions? If the regression was introduced by a vendor’s change, the vendor should fix it at no extra charge. If it pre-dates the vendor relationship, it’s typically billed separately.

Is there a tool to check my regression risk? Yes. Tuesday’s Website Regression Risk Checker gives you an assessment of your site’s current regression exposure based on platform, change frequency, and testing history.

Is there a service that does regression testing on every change? Yes. Tuesday’s Core Plan includes full regression QA on every change request as a standard feature, starting at $199/month.

Written by the Tuesday team — specialists in website maintenance and care plans for SMBs, with 500+ sites maintained across Wix, WordPress, Webflow, and Shopify.

Find out your site’s regression risk. Check your regression risk →