Keystone fits any store and any sector: electronics, fashion, home, beauty, sport, toys, books and marketplaces.
One design, your look: pick one of twelve colour schemes and fine-tune any colour in the native Theme Editor, every part of the storefront follows. Choose the Market, Classic or Showcase layout in one click; all three are normal Block Manager layouts. The demo store is a complete electronics shop.
One design, twelve colour schemes
Keystone is one design. Each colour scheme recolours the whole storefront from the Theme Editor colours: menu bar, buttons, badges, hero and footer. Open any of them in the live demo.
Mega menu with icons, labels, brands, deals and banners
Vertical catalog beside the hero
Promo cells inside the product grid, per category
Product of the day and promotions with days left
Colour swatches of variations on every card
Active filter chips and show more products
Quick view, wish list, compare, one-tap add
Mobile Buy and Filter bars
Full page cache safe, text contrast of at least 4.5:1
How it works
Install the package in Add-ons and activate Keystone in Website, Themes. The next admin page adds a demo store, so every section is filled at once.
Open Website, Keystone theme: click a layout (Market, Classic, Showcase) and a colour scheme. Sections, banners and menus are normal blocks: move them in the Block Manager, give a category its own promo cells, add icons and labels to menu items with a class, hide card elements per device in the settings.
Features
One modern classic design for every sector
Twelve colour schemes including a dark one
Every colour follows the native Theme Editor
Three layouts: Market, Classic and Showcase
Installs with full demo content: every section and demo products are ready after activation
Mega menu with category pictures or line icons, labels, top brands, best deal and banners
Vertical catalog with flyouts and a sticky header
Live search with pictures, prices, stock and categories
Promo cells inside the product grid: banner, countdown promotion, article or video popup
Cells one or two columns wide, set per category
Product of the day with a countdown
Active promotions carousel with days left
Category tiles, mosaic banners and subcategory chips
Product tabs, deal countdown band, promo banners and shop the set
Stickers: sale, new, bestseller and core labels
Colour swatches of product variations on cards
Product code and stock status on cards
Card elements hidden per device in the settings
Active filter chips and a show more button
Product videos in the gallery and a trust block
Frequently bought together with one add-to-cart button
Mobile Buy bar, filter sheet, drawer menu and bottom bar
Multi-Vendor shop header and shops row
Installs with a full demo store
Child of Responsive: add-on hooks keep working
CS-Cart and Multi-Vendor 4.17.2 to 4.21.x
What you get
Package
kv_theme_keystone-1.0.0.zip: the theme and its wrapper add-on, installed through Add-ons → Manage add-ons. Activate it in Website → Themes, then pick a layout and a colour scheme in Website → Keystone theme.
Editions
CS-Cart, CS-Cart Ultimate, Multi-Vendor and Multi-Vendor Ultimate 4.17.2 – 4.21.x, one package. A child theme of Responsive: no core files are changed and add-on templates keep working.
Updates & support
12 months included. Updates keep the theme files you changed; your layouts are never replaced.
License
1 production installation; subdomains, staging, dev and localhost are free. The theme checks its license for your domain once a day from the admin panel. Without a valid license the storefront shows the standard Responsive look instead of the Keystone design; cart, checkout and orders keep working. How licensing works
Compatibility
We list only the builds we install and test on. “Tested” means the full test plan was run on that build; “Supported” means the build is inside the supported range and uses the same hooks.
CS-Cart version and edition compatibility
CS-Cart version
CS-Cart
CS-Cart Ultimate
Multi-Vendor
Multi-Vendor Ultimate
4.22 and later
Testing next
Testing next
Testing next
Testing next
4.21.2
Supported
Supported
Tested
Supported
4.20.x
Supported
Supported
Supported
Supported
4.19.x
Supported
Supported
Supported
Supported
4.18.x
Supported
Supported
Supported
Supported
4.17.2
Tested
Supported
Tested
Supported
Before 4.17.2
Not supported
Not supported
Not supported
Not supported
Last tested build: Multi-Vendor 4.21.2, Oct 29, 2026Tested on: CS-Cart 4.17.2, Multi-Vendor 4.17.2, Multi-Vendor 4.21.2
Requirements
Platform
CS-Cart or Multi-Vendor 4.17.2 to 4.21.x (Ultimate editions included)
PHP
PHP 7.4 to 8.3
Platform
Standard CS-Cart add-ons used by the homepage: Banners (hero, side banners, promo banners, menu banners, promo
Core changes
None. Hooks and template overrides only
1.0.0
Oct 29, 2026
Latest
Added 10
Keystone theme: one modern classic storefront design for every sector (child of Responsive), CS-Cart and Multi-Vendor 4.17.2 to 4.21.x.
Twelve colour schemes (Theme Editor styles: Ocean, Graphite, Emerald, Coral, Sunrise, Ruby, Teal, Indigo, Forest, Rose, Volt, Midnight); every colour of the theme follows the Theme Editor colours.
Three Block Manager layouts (Market, Classic, Showcase) and the page Website > Keystone theme to switch layout and colour scheme.
Mega menu with category pictures or line icons, labels, top brands, the best deal and banners; vertical catalog; Catalog button; sticky header; live search.
Homepage sections: hero slider with price sticker, side banners, promises, category tiles and mosaic, product of the day, active promotions with days left, product tabs, deal countdown, promo banners, shop the set, compact products, brands, reviews, blog posts, Multi-Vendor shops.
Promo cells inside the product grid (one or two columns, countdown promotions, article and video popups), per category.
Product cards with product code, stock status, stickers, variation colour swatches, quick view, wish list, compare and one-tap add; card elements hidden per device.
Active filter chips, "Show more products", subcategory chips, filter sheet, Buy bar, drawer menu and bottom bar on phones.
Product page trust block and frequently bought together; Multi-Vendor vendor store header.
Demo content on activation: the Northwire electronics store (79 products with variations, promotions, banners, blog, reviews).
Tested on CS-Cart 4.17.2, Multi-Vendor 4.17.2, Multi-Vendor 4.21.2. First release.
Is Keystone only for electronics stores?
No. Keystone is one universal design; the demo store happens to sell electronics. Pick a colour scheme and a layout, replace the demo texts and banners with yours and it fits fashion, home, beauty, sport, toys, books or a marketplace.
Can I use my own brand colour?
Yes. Pick the closest scheme, then change the colours in Website > Themes > Theme editor (Primary button, Menu, Link, Background, Footer). Every Keystone colour follows them. Save it under a new name to keep the original scheme.
What is the difference between the three layouts?
Market has a Catalog button, a menu bar in your brand colour and the vertical catalog beside the hero; Classic has a search-led header, menu bar and a wide hero with side banners; Showcase has a one-row header and a large split hero. Products, banners and texts are shared, so you can switch any time.
Do I lose my changes when I switch layouts or schemes?
No. A layout is created once and then kept; schemes only change colours.
How do I show a different promo cell in one category?
Open the category's Layouts tab (or the per-category content of the "Grid promo cells" block in the Block Manager) and choose other banners there.
Does Keystone work with the full page cache of CS-Cart 4.21?
Yes. Pages print no visitor data; countdowns and filter chips are computed in the browser.
Does it work on Multi-Vendor?
Yes, including styled vendor store pages and a shops row on the homepage.
What happens without a licence?
The storefront shows the standard Responsive look; cart, checkout, orders and accounts keep working, and the admin shows a notice with the reason and the fix.
Can I turn the demo content off?
Yes: turn off Install the demo content when the theme is activated in the add-on settings before you activate the theme. Demo items you already have are normal products and pages; delete them in the standard admin pages.
What size should my product photos be?
At least 1200 x 1200 px. On activation Keystone sets the product page picture to 600 px and the product list picture to 360 px (Settings > Thumbnails); phones and retina screens load them at double size, and CS-Cart adds empty space around a photo that is smaller than that instead of enlarging it. Square photos on a white or transparent background look best in the light picture wells of the cards.
How do customers sign out?
The stock account menu is replaced by the labelled header icons; for a signed-in customer Keystone adds Sign out next to My account and to the account links in the footer.
A Swiss-editorial storefront theme with a shop-window homepage, oversized type and four bold styles, built on Responsive so every add-on keeps working.
A department-store theme for large catalogues: colour-coded departments, a department list beside the hero, tabbed product blocks and a sticky buy box.
