CS-Cart and Multi-Vendor Upgrades That Keep Your Add-ons, Theme and Customizations
We upgrade your CS-Cart store to the current version together with the parts that usually break in an upgrade: third-party add-ons, the UniTheme2 theme, core modifications and integrations. The price depends mostly on how much custom work built for your store has to be upgraded by hand.
Free estimate · from $240 with no custom code · done on a copy of your store
- CS-Cart 4.21.2released September 22, 2026current
- CS-Cart 4.12–4.20still getting security updatestime to plan
- CS-Cart 4.11 and olderno patches since January 1, 2024unsupported
- PHP 8.3from CS-Cart 4.19.1, supported until the end of 2027target
- PHP 8.2security updates until the end of 2026until year-end
- PHP 8.1 and olderno security updatesunsupported
When it is time to upgrade CS-Cart
Four signs that the upgrade should not wait.
Version 4.11 or older
CS-Cart has released no security patches for it since January 1, 2024: every vulnerability found stays open.
Your host is retiring old PHP
PHP 8.1 no longer gets security updates, and 8.2 gets them only until the end of 2026. PHP 8.3 runs only with CS-Cart 4.19.1 and later.
New add-ons will not install
New add-ons and integrations need a current core: many of our add-ons require CS-Cart 4.17.1 or later.
Payment and shipping APIs change
Payment gateways and shipping carriers move to new API versions, and add-ons for old CS-Cart versions do not keep up.
What a CS-Cart upgrade includes
Upgrading the core is easy. The real work is everything around it.
CS-Cart and Multi-Vendor core
Through the Upgrade Center, version by version, on a copy of your store. Built-in add-ons and language packs are upgraded together with the core.
Cart-Power add-ons
We install the ready versions for the new core. Add-ons written for your store are adapted to the API and hook changes.
Add-ons from other developers
AlexBranding, eCom Labs and others: if there is a version for the new core, we install it and you buy the license. If not, we adapt the add-on or replace it with a built-in one.
Theme
We upgrade UniTheme2 and its companion add-ons as a package and carry your template changes over to the new theme version.
Core modifications
We find each one by comparing your files with the original distribution of your version, and carry it over so the upgrade does not overwrite it.
Integrations and server
ERP and accounting sync, payments, shipping, cron jobs, PHP version and server settings: we check them and carry them over.
How this differs from an upgrade by CS-Cart
An upgrade is also part of CS-Cart's own technical support. The difference is in what it leaves out.
CS-Cart support
Installs the new version under a support subscription. But, as the vendor itself states, it does not fix issues with third-party add-ons, themes and customizations that come up after the upgrade.
Cart-Power
That is exactly what we take on: third-party add-ons, the theme and customizations. After the upgrade your store works the same as before, only on the new version.
What we find when we inspect a store
Five findings from our 2026 estimates. Each one would have broken the store in a blind upgrade.
About 830 redirects in index.php
Manual 301 redirects lived right in a core file. The upgrade would have overwritten it, and the old URLs would have started returning 404. We move them where the upgrade cannot touch them.
18 of 27 add-ons were custom-built
Ready-made Cart-Power add-ons are upgraded by installing the new version. Add-ons written for the store are upgraded by hand, and they took two thirds of the add-on work.
“Customized” shipping add-ons
Copies of two shipping add-ons looked modified, but the comparison showed no real changes. We switched them to the standard versions: less work now and fewer problems later.
The store will not start on PHP 8.3
CS-Cart 4.18 checks the PHP version at startup and shows a blank white screen across the whole site on 8.3. If the host upgrades PHP on its own, the store goes down.
The hosting panel reset the settings
When the PHP version changed, the panel recreated the pool: 5 processes instead of 20, and the form field limit was gone. Without it, the admin panel cannot save products with many options.
We will check your store
We find spots like these before the upgrade, not after it. The inspection and estimate are free.
Send two screenshots and we will estimate your upgrade
Your add-on list and the File changes detector screen show how much custom work needs a manual upgrade. Estimate within 1–2 business days.
How a CS-Cart upgrade works
Your live store keeps selling while we work on a copy.
Third-party add-ons, core and theme modifications, PHP version, integrations. The result is an estimate for each add-on.
The core version by version, then add-ons, the theme and modifications. We check them against the APIs and hooks of the new version.
Catalog, search, cart, payment, shipping, customer account and ERP sync, following your store's own scenarios.
At night, with a fresh backup and a rollback plan. The store closes only for the final switchover.
What makes up the upgrade price
The cost of a CS-Cart upgrade has three parts. Two are predictable; the third depends on how much in the store was written specifically for you.
Licenses
The CS-Cart upgrade subscription, the theme and add-ons from other developers. You pay their authors at their prices, and we tell you what to renew.
at the developers' prices
+ Platform and data transfer
Core and built-in add-ons, the theme and ready-made add-ons, data and settings transfer, testing and go-live. Depends little on the store.
from $240
+ Manual upgrade of custom code
Add-ons and modifications written for your store: we adapt each one by hand. Usually 1–3 hours per add-on, with a separate estimate for each.
from $30 per add-on
How much a CS-Cart upgrade costs
Four stores from our practice: the more custom work in the store, the more the upgrade costs.
Scroll the table sideways →
| Upgrade | What the store has | Upgraded by hand | Cost of work |
|---|---|---|---|
| 4.18 → 4.21 | UniTheme2 theme and 30 AlexBranding add-ons, 4 third-party add-ons | 1 add-on and 2 core modifications | $320 |
| 4.13 → 4.21 | UniTheme2 theme and 16 AlexBranding add-ons; an older version means more intermediate steps | 1 core modification | $520 |
| 4.17 → 4.21 | 15 Cart-Power add-ons, the theme and 29 AlexBranding add-ons, 20 add-ons from other developers | 6 custom features for the store | $850 |
| 4.15 → 4.21 | 35,000 products, ERP sync, 9 ready-made Cart-Power add-ons | 18 add-ons built for the store | $1,750 |
Prices cover the work only, excluding licenses. You buy the licenses (the CS-Cart upgrade subscription, the theme and other developers’ add-ons) directly from their authors.
Upgrades we have done
Two projects where the upgrade was the main task.
Herbariasoap
We upgraded the store to CS-Cart 4.18 with no loss of data or customizations and reworked outdated templates along the way. Two rounds of testing before go-live.
K9 Shop
We have supported this store for many years and upgrade it as new versions come out: from CS-Cart 4.1.3 to 4.16.1, with customizations for the client's business.
Your store could be next
Send us screenshots of your add-ons and we will come back with an estimate.
Questions about CS-Cart upgrades
Answers to what clients ask before ordering.
The price is made up of licenses, the platform upgrade with data transfer (from $240) and the manual upgrade of custom code: each add-on written for your store usually adds 1–3 hours. We prepare an estimate for your store free of charge.
A store on 4.18 with a theme and about thirty add-ons takes 4–7 business days; one on 4.17 with integrations, 8–12. Older versions with customizations take longer, and the estimate states the timeline.
Yes. Upgrades are included in the license for the first year; after that CS-Cart sells a subscription. You buy it, and we tell you which one you need.
Yes, in a single project: we install the intermediate versions one by one on a copy and move only the final result to production. That is how we upgraded stores from 4.4 and 4.13 to 4.20.
If the developer has a version for the new core, we install it and you buy the license. If not, we adapt the add-on ourselves or replace it with a built-in one.
Yes. The data stays in the same database and the URLs do not change. We find manual redirects and modifications during the inspection and carry them over.
Only within what your version supports: PHP 8.2 from CS-Cart 4.18.1, PHP 8.3 from 4.19.1. An old version will not start on a newer PHP.
Yes. For Multi-Vendor we also check the vendor panel, commissions and payouts; for multiple storefronts, each theme and the storefront settings.
Yes. We find out at which step and why the Upgrade Center stopped, restore the store from a backup if needed and complete the upgrade on a copy.
Yes, all work is done on a copy. The store closes only for the final switchover: at night, with a fresh backup and a rollback plan.
Client reviews
What store owners write about our work and our add-ons on the CS-Cart Marketplace.
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a CS-Cart upgrade
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