Installation

Requirements

• CS-Cart or CS-Cart Multi-Vendor 4.17.2 – 4.21.x (tested on CS-Cart Ultimate 4.17.2 with PHP 8.1, Multi-Vendor 4.17.2 with PHP 8.1 and Multi-Vendor 4.21.2 with PHP 8.3).
• PHP 7.2.5 – 8.3, as supported by your CS-Cart version.
• At least one way to write WebP or AVIF with PHP: the GD extension with WebP support (standard on most hosts), or Imagick. AVIF needs PHP 8.1 or newer with AVIF in GD, or Imagick with AVIF. The add-on checks this for you (see Server support).
• No external programs and no exec(): hosts that disable shell functions are fine.
• The images of the store on the server’s file system (the default). A CDN in front of the store works.
• Disk space for the copies: roughly half to two thirds of the size of your images/ folder for WebP and AVIF together (copies that would not be smaller are not kept).
• No other add-on is required.

Install

1. Go to Add-ons → Manage add-ons, click the gear button and choose Manual installation.
2. Upload kv_image_optimizer_webp-<version>.zip and click Upload & install.
3. On the License tab of the settings, enter your license key and save. If you bought the add-on on the CS-Cart Marketplace and entered the license number in Add-ons → Manage add-ons, you can skip this step. Until a key is verified, the add-on works for 14 days (see License).
4. Open Website → Image optimizer and click Optimise now. The page scans the images/ folder and converts the images in short batches with a progress bar. You can leave the page at any time: the work continues later.
5. Recommended for larger catalogs: add the cron line shown on the page (for example every 15 minutes). Without cron, the add-on works in short background batches while an administrator uses the admin panel.

Installation creates one table (cscart_kv_iow_files, the list of images with their sizes and status). The copies go to images/kv_image_optimizer_webp/, work files and backups to var/kv_image_optimizer_webp/. No core files, core tables or original images are changed.

Right after installing, the storefront still shows the original images: an image gets its WebP/AVIF sources as soon as its copies exist. Lazy loading and the priority of the main product image work at once.

Upgrade

Upload the new package over the installed add-on (same steps as installing). On the next admin page load the add-on brings its table, settings and language variables up to date by itself. The copies, the statistics and the backups of compressed originals are kept.

Disable

Disabling the add-on (status Off) makes the storefront show the original images again without any change to the markup. The copies stay on disk and are used again when you turn the add-on back on. To keep the add-on active but stop serving the copies, set Serve optimised images to Off.

Uninstall

Add-ons → Manage add-ons → Image Optimizer (WebP/AVIF & Lazy Load) → gear → Uninstall:

1. puts every original that Compress original images rewrote back from its backup (an image you replaced since then is kept as it is);
2. deletes all WebP and AVIF copies (images/kv_image_optimizer_webp/) and the work files (var/kv_image_optimizer_webp/);
3. removes the table, the settings and the language variables.

Your original images, thumbnails and all other store data are never deleted. For a very large number of compressed originals, run Restore originals on the image optimizer page first, so the uninstall itself has little to do.