Magento 2 Update Product Stock Inventory by Rest API.

You can Update Product Stock related information by REST API with the use of endpoint URL /V1/products/:productSku/stockItems/:itemId.

You can manage Stock Inventory related data with REST API with the given payload as below.

Action: PUT

Header: Authorization: Bearer <ADMIN_TOKEN>

URL<BASE_URL>/V1/products/:productSku/stockItems/:itemId
(Example, https:/magento246.test/rest/V1/products/24-MB01/stockItems/90)

You can fetch itemId by calling the GET Product StockItems API. Product Stock Item by REST API V1/stockItems/:SKU Magento 2?

PAYLOAD:

{
  "stockItem": {
    "product_id": 12,
    "stock_id": 1,
    "qty": 1030,
    "is_in_stock": true,
    "is_qty_decimal": true,
    "use_config_min_qty": true,
    "min_qty": 0,
    "use_config_min_sale_qty": 0,
    "min_sale_qty": 0,
    "use_config_max_sale_qty": true,
    "max_sale_qty": 0,
    "use_config_backorders": true,
    "backorders": 0,
    "use_config_notify_stock_qty": true,
    "notify_stock_qty": 0,
    "use_config_qty_increments": true,
    "qty_increments": 0,
    "use_config_enable_qty_inc": true,
    "enable_qty_increments": true,
    "use_config_manage_stock": true,
    "manage_stock": true,
    "low_stock_date": "",
    "is_decimal_divided": true,
    "stock_status_changed_auto": 0,
    "extension_attributes": {}
  }
}

All the fields are self-explanatory. You can set qty, is_in_stock to set your product In stock and Qty value.

RESPONSE: Item Id.