# SKU canonicalization > Normalizing product codes to one form before matching, so one product never becomes several items. Also known as: canonicalization. Category: E-commerce and workflow. Canonicalization converts identifiers to a single standard form, for example by trimming, uppercasing and removing special characters, before comparing them. Without it, sku_12345 and SKU-12345 look like different products. ## How PhotoRobot uses it Integrators canonicalize SKUs from the upstream system before importing a [shooting list](https://www.photorobot.com/glossary/shooting-list), so PhotoRobot does not create duplicate items. Covered in module [I03, Shooting List & SKU Lifecycle](https://www.photorobot.com/academy/curriculum#i03-shooting-list-sku). ## Related terms - [SKU (stock keeping unit)](https://www.photorobot.com/glossary/sku): A retailer's internal code for one distinct product variant. - [Shooting list](https://www.photorobot.com/glossary/shooting-list): The list of items to be photographed in a project, usually imported from a spreadsheet. - [Mapping table](https://www.photorobot.com/glossary/mapping-table): An integrator's table linking canonical SKUs to PhotoRobot item IDs and external IDs. - [External ID](https://www.photorobot.com/glossary/external-id): The customer's own product identifier stored with a PhotoRobot item, for syncing status back.