Set absolute on-hand inventory quantities for a product variant across Shopify locations using the inventorySetQuantities Admin GraphQL mutation

In-depth guide

Steps

1. Query `inventoryItem(id: $inventoryItemId)` or `productVariant.inventoryItem` to retrieve the inventory item ID for the variant you want to update
2. Fetch the current `on_hand` quantities per location via `inventoryLevel.quantities(names: ["on_hand"])` on the inventory item to get current values for compare-and-swap
3. Call `inventorySetQuantities(input: { name: "on_hand", reason: "correction", quantities: [{ inventoryItemId: $id, locationId: $locationId, quantity: 50, compareQuantity: 45 }] })` — the `compareQuantity` acts as an optimistic lock to prevent overwriting concurrent updates
4. Check `inventorySetQuantitiesPayload.userErrors`; a `compareQuantity` mismatch error means another process updated the inventory between your read and write — re-fetch and retry
5. Use `reason` values such as `correction`, `received`, or `damaged` to annotate the reason for the quantity change; this appears in the inventory history log
6. For bulk updates across many variants and locations, batch multiple `quantities` entries in a single mutation call rather than making one call per variant