Definition
A license key is a unique string a software vendor issues to a paying customer to prove that an installation is authorized. The application validates the key with the vendor's licensing server, which returns an entitlement - typically the plan tier, active add-ons, and a seat count describing how many installations are allowed. Modern license systems cache entitlements locally so the software works offline and only re-checks periodically.
License keys differ from API keys in purpose: a license key unlocks features for a customer, while an API key authenticates an integration call. License keys are rarely secret in the same way - leaking one allows unauthorized use of a paid product, but does not grant access to private data.
How SheetLinkWP relates to License Key
SheetLink Forms license keys look like slkey_ followed by 32 hexadecimal characters. When you enter one under SheetLink > License, the plugin contacts SheetLinkWP, registers the site against your seat count, and caches the returned entitlement for 12 hours. The entitlement tells the plugin which add-ons to enable (CRM Fan-Out, Two-Way Sync, WooCommerce Sync, White-Label, etc.) and which UI elements to show. If you move a site to a new URL, you can deactivate the old site from the customer portal to free up the seat. See the license activation guide for full details.