Black Friday eCommerce Checklist: What Breaks and How to Prepare

• Most Black Friday incidents aren't caused by traffic. They come from last-minute changes: a new app, a discount set up the night before, a rushed banner, a new tracking script.
• Peak minutes are expensive. Shopify merchants sold $5.1 million a minute at the Black Friday 2025 peak, and US shoppers spent $16 million a minute online at the Cyber Monday peak. An hour of broken checkout never costs more than it does that weekend.
• The usual suspects: checkout apps, API limits, bots, custom checkout logic rebuilt on Shopify Functions, search and filter vendors, third-party scripts, content changes, late releases, and the order flow after checkout.
• The fix is boring and it works. Test every discount and Shopify Function with real orders, freeze code and apps, protect pages from failing scripts, map what happens after checkout, and have someone on call at 2am on Saturday.

Every year we spend Black Week on call for our Shopify Plus clients. And every year the pattern repeats. The store handles the traffic, and something small breaks it anyway. An app that shows as disabled but is still active in checkout. A cookie banner that crashes product pages for one country.

Marketing checklists will tell you what to promote and when to send the emails. This one is about making sure the store is still standing when they go out. It's built from incidents our engineers have handled for fashion, apparel and tech brands, anonymized, and the week-by-week routine we now run to prevent them.

Black Week is when a minute of downtime is priced highest. Here is how much money moves through those days, and how much of it leaks when the site misbehaves.

Sources: Shopify BFCM 2025, Adobe Cyber Monday 2025, Baymard Institute, Deloitte for Google, Milliseconds Make Millions.

To price it for your own store, add up three things: your peak hourly revenue times the hours the problem lasts, the ad spend that keeps running while it lasts, and the margin you lose on orders that do go through.

A simple example. Take a brand that books $30,000 an hour on Black Friday and loses checkout for 8 hours, as the fashion brand in problem 1 did. That's about $240,000 in missed orders, while every paid campaign keeps sending traffic to a store that can't take payment. And not every loss shows up as an outage. Orders that go through but never reach the warehouse system turn into late shipments and support tickets. A page that slows down under sale load loses conversion on every session, and no alert fires.

These are the nine problems we see most. Most come with an incident we've handled, and each comes with the prevention we now run as standard.

1. Checkout or cart breaks

Zero revenue until it's fixed, while paid traffic keeps burning. This is the most expensive failure on the list, and the one where every minute counts.

What we've seen: a fashion brand lost checkout for over 8 hours. A cross-border app's checkout extension was still active, even though the app showed as disabled in the admin.

Prevention: a full test run of cart and checkout before the event, checkout monitoring, and one named person who escalates to Shopify and the app vendor.

2. Too many requests to Shopify or other APIs

Product or category pages error out, exactly at peak. Shopify and most vendors limit how often you can call them, and sale traffic multiplies every call your pages make.

What we've seen: an apparel brand's product pages all returned errors on a sale weekend. Shopify throttled an endpoint the page called too often.

Prevention: audit API calls per page, cut background prefetching, and make sure one failing service can't take the whole page down.

3. Bot traffic and sudden spikes

A slow site, and hosting or CMS bills that jump. Bots arrive before the sale too, checking prices and stock.

What we've seen: a tech brand got about 10x its normal bot traffic ten days before Black Friday. That caused around 50 million cache rebuilds.

Prevention: bot protection, cache and usage alerts, and vendor quotas confirmed for the event window.

4. Custom checkout logic after the move to Shopify Functions

This is the first Black Friday without Shopify Scripts. Shopify stopped running them on 30 June 2026, so every custom discount, shipping and payment rule now runs on Shopify Functions. For many brands that logic was rebuilt this year and has never seen sale traffic.

What to watch: tiered discounts, bundles, free shipping rules and payment rules ported from Scripts. A rule rebuilt as a Function doesn't always behave exactly like the Script it replaced, and you find out on the first order that hits the edge case.

Prevention: list every rule that moved from Scripts, test each one with real orders across products, customer groups and markets, and check how it stacks with your Black Friday codes before the freeze.

5. Search or filters fail

Missing filters, and empty or wrong category pages. Shoppers can't find the sale, so they leave.

What we've seen: a search vendor that didn't update inventory in real time. A backup filter setup that worked on staging but not in production. Filters that failed for shoppers arriving from email links.

Prevention: a fallback for the peak window. When the external search tool can't keep up, the site switches to Shopify's own API. Some errors still happen, but category pages stay up, and that's the point. Test the fallback in production, and test campaign links with their tracking parameters before every send.

6. A third-party script or app breaks pages

Often only for some visitors, some countries, or ad-blocker users. So it hides from your own team, who are logged in, in one country, with cookies accepted.

What we've seen: a consent tool change locked some visitors out for a week. A cookie banner crashed every product page for EU visitors who hadn't accepted cookies. A vendor's script was compromised and served malicious code.

Prevention: no new apps or scripts during the freeze, guards so a failing script can't crash the page, and a review of the consent setup in every market.

7. A content or campaign change breaks the layout

Your homepage looks broken to the biggest audience of the year.

What we've seen: an old promo banner left live in two markets. Sale navigation that didn't render.

Prevention: preview every content change in every market, and have an engineer on hand for urgent banner swaps.

8. A last-minute release or upgrade

A small change takes down a core flow.

What we've seen: a dependency update sent shoppers from the country selector to a 404 page. A CMS limit change took a site down for 2.5 hours after a routine deploy.

Prevention: a code freeze, smoke tests on key flows after any change, and a rollback plan.

9. Orders go through, then get stuck after checkout

The storefront is fine and checkout works. The problem sits behind it. Sale volume backs up webhook queues, the ERP or warehouse sync falls behind, and custom order emails go out hours late.

What it looks like: inventory that doesn't sync fast enough, so you oversell. Stale stock or prices on the site. Order confirmations delayed. Bot and fraud orders that get through checkout and have to be cancelled by hand. For one streetwear brand we built a tool that helps their team handle those orders after purchase.

Prevention: map every step after checkout: webhooks, ERP and warehouse sync, order emails, fraud review. Find the weakest link, usually an external connection, a third-party vendor or a custom endpoint. Load-test that path, or at least know what happens when it slows down and how you catch up.

Work back from the sale date. Everything risky happens before the freeze. Everything after it is testing and watching.

4 weeks before

• List every campaign, discount, bundle and gift-with-purchase planned for Black Week, with dates and markets
• Audit apps and scripts: remove what you don't use, and check that "disabled" apps have no checkout extensions, Functions, pixels or theme app embeds still active
• Audit API calls per page (Shopify, search, reviews, CMS)
• Turn on bot protection and set cache and usage alerts with your hosting and CMS vendors
• Confirm event-window quotas and support contacts with every critical vendor
• List every custom discount, shipping and payment rule that moved from Scripts to Shopify Functions this year

2 to 3 weeks before

• Test every discount and Shopify Function with real orders: right products, right stacking with your Black Friday codes, right customer groups, every market
• Test search and filters in production, including the fallback to Shopify's API if your search vendor fails
• Review the consent setup and cookie banner in every market, with and without consent given
• Add guards so a failing third-party script can't crash a page
• Map the order flow after checkout (webhooks, ERP, warehouse, order emails, fraud review) and load-test the weakest link
• Agree the code freeze dates and an escalation sheet: who to call, who approves what

Week before: freeze

• Code freeze and app freeze: no new apps, scripts, themes or dependency updates
• Full test run of cart and checkout in every market and payment method
• Test every campaign email link, with tracking parameters, through to checkout
• Preview homepage, navigation and sale pages in every market
• Write the rollback plan for each planned content change

Day before

• Dry run of every sale that launches tomorrow
• On-call rota confirmed: engineer per shift, backup, and escalation to a tech lead
• Shared channel open with the brand team, engineers and key vendors
• Shopify support route ready: the Plus priority phone line if you're on Plus, and Shopify's status page bookmarked

When something breaks at 2am, the first question is how bad it is. Not everything is an emergency, and treating a banner glitch like a checkout outage pulls engineers off the problem that costs money. This is the model we run on call.

Three habits matter more than the table:

1. One shared channel where anyone, from the brand team to the engineers, can flag a problem.
2. One person who talks to Shopify support and the app vendors, so nobody is waiting on three separate tickets.
3. No fix goes live without a smoke test, even at 3am. A rushed fix is a last-minute release, and that's problem number 8.

Shopify support is part of your on-call team

Every Shopify plan includes 24/7 support, so help is there at 2am on Black Friday. In our experience the team responds fast and knows the platform well. They can see what's happening on the platform side and help you work out whether the cause is Shopify, an app or your own code, which makes triage much quicker.

On Shopify Plus you get priority 24/7 phone support (Shopify pricing), so your case goes to the front of the queue when it matters most.

Write it down within a week, while people still remember the details. Every incident, how fast it was answered, uptime, and what to fix before the next peak. Most of next year's checklist comes from this list.

Is Shopify down on Black Friday or Cyber Monday?

Rarely, but it happens. On Cyber Monday 2025 a login problem locked some merchants out of their Shopify admin and disrupted POS for much of the day. Shopify said checkout and storefronts stayed online (Engadget). In the incidents we've handled, the cause was almost always on the store's side: an app, a script, custom checkout logic or a last-minute change. So check Shopify's status page first, then look at your own stack.

How much does downtime cost on Black Friday?

Multiply your peak hourly revenue by the hours affected, then add the ad spend that kept running and the cost of orders you later cancel, refund or ship late. For a brand doing $30,000 an hour at peak, an 8-hour checkout outage is about $240,000 in missed orders before ad spend.

When should we start preparing for Black Friday?

Four weeks out at the latest. Discounts, apps and integrations need testing before the code freeze, and the freeze should start about a week before the sale.

What is a code freeze?

A period before a big sale when no new code, apps, scripts or theme changes go live, except fixes for real incidents. It removes the most common cause of peak-weekend failures.

Do we need 24/7 support for Black Week?

If a few hours of broken checkout would cost more than the cover, yes. Incidents often hit at night and at weekends, when normal support is closed.

Our retainer clients get engineers on call 24/7 in their Slack for Black Friday or the whole of Black Week, with a readiness check the week before and a report after. If you're not a client yet and want a second pair of eyes on your setup before 27 November, talk to us.