PrestaShop 9 migration and new theme for Tellknives
A Swiss online knife store with 10,000 products, moved from PrestaShop 8.1 to 9.1, with a Hummingbird child theme true to its brand guidelines, a catalogue synchronised with its management tools and VAT handled correctly for Switzerland and export. 12,800 customers and 17,900 orders carried over, with no data migration on launch day.
The Challenge
Tellknives sells knives, tools and outdoor equipment from Switzerland, in French, German, Italian and English. The catalogue holds more than 10,000 products and nearly 7,000 combinations, fed automatically from the product management tool and from the suppliers' stock files. The store takes orders every day, by card and by TWINT.
It ran on PrestaShop 8.1 with a Falcon-based theme that was no longer maintained, 80 modules, some of them written by former agencies, and core overrides that PrestaShop 9 no longer accepts. The site applied almost none of the brand's visual guidelines.
The brief came down to four points: move to PrestaShop 9, modernise the design while respecting the brand guidelines, keep all data and all flows (catalogue, payment, shipping, stock imports) and keep selling throughout.
It ran on PrestaShop 8.1 with a Falcon-based theme that was no longer maintained, 80 modules, some of them written by former agencies, and core overrides that PrestaShop 9 no longer accepts. The site applied almost none of the brand's visual guidelines.
The brief came down to four points: move to PrestaShop 9, modernise the design while respecting the brand guidelines, keep all data and all flows (catalogue, payment, shipping, stock imports) and keep selling throughout.
Our Solution
The whole project was carried out on a full staging copy, hosted on the same server, with e-mails cut off, payments in test mode and robots excluded. Every night it received a fresh copy of the live store: 232 tables copied and checked, zero differences, in two minutes. The client was therefore always working on her real data.
PrestaShop 9 removes 56 classes and 90 public methods from version 8. Every override and every module was reviewed against that list: the useful overrides were realigned with PrestaShop 9, those no longer needed were removed, and the old theme's modules were replaced by their native equivalent where one existed.
The design starts from the brand guidelines: Tellknives red, military green and the Outfit typeface. The mock-up approved by the client was built into a child theme of Hummingbird, the official PrestaShop 9 theme, keeping what the old theme did well (mega menu, "Ask our experts" block, gift card). With lighter fonts and 27,000 images converted to WebP, pages weigh 5 to 10 times less, load twice as fast and make 35% fewer requests.
Where no existing module fitted, we wrote our own, native to PrestaShop 9. Sharp Users is the space for the brand's ambassadors, with their profiles, articles submitted and reviewed before publication, and participation levels. The export VAT module applies the 8.1% Swiss VAT to Switzerland and Liechtenstein, lets other countries order without VAT and shows an estimate of import VAT from the cart onwards. A last module translates the catalogue into the four languages, with DeepL or AI.
The 9,811 catalogue prices were converted to prices excluding VAT, and a sample of 80 prices was checked identical before and after. The customers' 522 wishlists (9,043 products) were carried over, PostFinance Checkout moved to version 2 and the euro was added alongside the Swiss franc. This work is as much custom development as it is e-commerce.
The store is monitored by PrestaSecure, our security solution dedicated to PrestaShop, on its Serenity plan: our team watches the store and steps in itself when an alert is raised. Files and modules are analysed on every scan, and any unexpected change is reported. A web application firewall filters requests before they reach PrestaShop. Any back-office login from a new location must be confirmed with a code, sent to a trusted address chosen by the client. Modules written by former agencies were reviewed and hardened before launch. The configuration was carried over and adjusted for PrestaShop 9 on switchover day.
PrestaShop 9 removes 56 classes and 90 public methods from version 8. Every override and every module was reviewed against that list: the useful overrides were realigned with PrestaShop 9, those no longer needed were removed, and the old theme's modules were replaced by their native equivalent where one existed.
The design starts from the brand guidelines: Tellknives red, military green and the Outfit typeface. The mock-up approved by the client was built into a child theme of Hummingbird, the official PrestaShop 9 theme, keeping what the old theme did well (mega menu, "Ask our experts" block, gift card). With lighter fonts and 27,000 images converted to WebP, pages weigh 5 to 10 times less, load twice as fast and make 35% fewer requests.
Where no existing module fitted, we wrote our own, native to PrestaShop 9. Sharp Users is the space for the brand's ambassadors, with their profiles, articles submitted and reviewed before publication, and participation levels. The export VAT module applies the 8.1% Swiss VAT to Switzerland and Liechtenstein, lets other countries order without VAT and shows an estimate of import VAT from the cart onwards. A last module translates the catalogue into the four languages, with DeepL or AI.
The 9,811 catalogue prices were converted to prices excluding VAT, and a sample of 80 prices was checked identical before and after. The customers' 522 wishlists (9,043 products) were carried over, PostFinance Checkout moved to version 2 and the euro was added alongside the Swiss franc. This work is as much custom development as it is e-commerce.
The store is monitored by PrestaSecure, our security solution dedicated to PrestaShop, on its Serenity plan: our team watches the store and steps in itself when an alert is raised. Files and modules are analysed on every scan, and any unexpected change is reported. A web application firewall filters requests before they reach PrestaShop. Any back-office login from a new location must be confirmed with a code, sent to a trusted address chosen by the client. Modules written by former agencies were reviewed and hardened before launch. The configuration was carried over and adjusted for PrestaShop 9 on switchover day.
Results
On 2 November 2026, no data had to be migrated: the staging copy, already up to date, became the store. Maintenance started at 10:11 and the store reopened to the public at 11:39, after acceptance testing carried out with the client.
The first PrestaSecure scan of the new store gave a security score of 100 out of 100.
The Tellknives team's feedback was handled the same day, as they tested: manual stock, Swiss Post labels, supplier stock imports, customer service. The next morning, a review of the logs revealed a catalogue synchronisation, written by a former agency, that was not compatible with PrestaShop 9. It was fixed within the hour, and the previous day's updates were replayed with no loss.
Another PrestaShop 9 migration carried out with the same method: the Ammerlaan Import store.
The first PrestaSecure scan of the new store gave a security score of 100 out of 100.
The Tellknives team's feedback was handled the same day, as they tested: manual stock, Swiss Post labels, supplier stock imports, customer service. The next morning, a review of the logs revealed a catalogue synchronisation, written by a former agency, that was not compatible with PrestaShop 9. It was fixed within the hour, and the previous day's updates were replayed with no loss.
Another PrestaShop 9 migration carried out with the same method: the Ammerlaan Import store.
Gallery
Project Details
- Client Tellknives
- Year 2026
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Technologies
PrestaShop 9 Migration Thème sur mesure Hummingbird Modules sur mesure Multilingue Reprise de données Sécurité
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