The plugin is a normal WooCommerce shipping method. It calculates rates through the standard shipping API and stays out of everything else, which is what makes it compatible with most of the ecosystem by default. The details below cover the questions that do come up.
Versions
Weight Based Shipping 6.18, released 1 day ago, is tested with:
WooCommerce 11.1 (requires 7.0+)
WordPress 7.1 (requires 5.8+)
PHP 7.3+, 8.x
Every release is tested against the current versions of all three. If a requirement is not met the plugin does not load, and says which one is missing rather than failing quietly.
New WooCommerce major releases occasionally change shipping internals. We track them, but on a live store it is sensible to let a new major version settle for a week or two before updating, as with any plugin.
Block cart and checkout
The block-based Cart and Checkout are supported. Rates reach them through the WooCommerce Store API, the same source the block checkout uses for every shipping method, so options, prices, and titles appear as they do in the classic templates.
Two differences are worth knowing while you test. The block Cart has no address fields and lists only the first option, so the checkout is the page to work from. And the per-shipment breakdown under a combined option is printed by a classic template hook, so it does not appear in the blocks.
HPOS (High-Performance Order Storage)
HPOS is supported and declared, so the plugin does not hold WooCommerce back from the modern order tables.
Translations
Two different things get called translation here.
The admin interface — column headings, buttons, editor labels — is English only. It is not prepared for translation, and there is no translation file to work from.
The shipping option titles that customers see are different: you type them yourself, in whatever language you like, and they are translatable with the usual multilingual plugins because WooCommerce exposes shipping method titles as translatable strings. Polylang and WPML both work this way. With WPML, enable String Translation and its automatic string registration, then load the cart or checkout once so that each title is actually produced — a title that has never been shown cannot be caught for translation. After that the titles appear among the translatable strings.
If you only need a different wording rather than several languages, rename the table or the rule title. That is the label customers see.
Multi-currency
Currency conversion belongs to your currency plugin: it converts product prices and the shipping cost alike. What the plugin adds in the Pro edition is conversion of Value thresholds, so a $100 free-shipping rule stays a $100 rule for a customer browsing in another currency. The common switchers are detected automatically.
Caching
Two caches matter. WooCommerce caches calculated shipping rates for a customer's session, so prices do not recompute on every page load. Saving your rules clears that cache; editing a product's weight does not, which is why a test cart can show a stale price after a product change. Turning on WooCommerce → Settings → Shipping → Shipping settings → Enable debug mode switches that cache off while you work. Turn debug mode off again when you are done; it is not meant for a live store.
Page caches are the other one. Cart and checkout must never be cached as static pages; every caching plugin excludes them by default, and a custom configuration that does not is worth checking when customers report prices that belong to somebody else's basket.
Other plugins
Other shipping plugins coexist without trouble: each contributes its own options and none can suppress another's. Payment gateways that filter on shipping method work normally, since the plugin's rates follow the standard WooCommerce identifier convention.
Marketplace and multi-vendor setups are only partly covered: rules are configured by the store owner rather than by each vendor, so the practical handle for per-vendor pricing is to give each vendor a shipping class.
Conflicts, when they happen, are nearly always about the admin screen rather than the rates. Another plugin printing a notice or an error into the settings page can leave the rules editor blank or unable to save. The fastest diagnosis is the standard one: deactivate other plugins, switch to a default theme, confirm the problem disappears, then restore them one at a time.
Running two copies
The free and Pro editions are the same plugin in different packages, and only one of them runs at a time. Activating one deactivates any other copy and shows a notice explaining what happened, so an accidental double install is a tidiness problem rather than a broken site. See Free vs Pro for the upgrade procedure.
For developers
Rates are added with the standard WooCommerce shipping API under the method identifier wbsng, so the usual filters apply — including woocommerce_package_rates for adjusting or removing rates before they reach the customer, and the per-method availability filter. The plugin exposes no hooks of its own; rule configurations live in WordPress options, one per shipping method instance, in the same structure the editor copies to the clipboard as JSON.