# Notifications

When initializing or running the engine, certain operations may take considerable time to complete.
You can receive progress notifications for these operations using a callback function.

Progress notifications are supported for model downloads, cache loads, and inference runs.

Below is an example of using the callback function with the image-to-text model:

```javascript
const { createEngine } = ChromeUtils.importESModule("chrome://global/content/ml/EngineProcess.sys.mjs");

// options needed for the task
const options = {taskName: "moz-image-to-text" };

// We create the engine object, using options and a callback
const engine = await createEngine(options, progressData => {
  console.log("Received progress data", progressData);
});
```

In the code above, **progressData** is an object of type `ProgressAndStatusCallbackParams` containing the following fields:

- **progress**: A float indicating the percentage of data loaded. Note that 100% does not necessarily mean the operation is complete.

- **totalLoaded**: A float indicating the total amount of data loaded so far.

- **currentLoaded**: The amount of data loaded in the current callback call.

- **total**: A float indicating an estimate of the total amount of data to be loaded.

- **units**: The units in which the amounts are reported.

- **type**: The name of the operation being tracked. It will be one of `ProgressType.DOWNLOAD`, `ProgressType.LOAD_FROM_CACHE`, `ProgressType.INFERENCE`.

- **statusText**: A message indicating the status of the tracked operation, which can be:

  - `ProgressStatusText.INITIATE` Indicates that an operation has started. This will be used exactly once for each operation uniquely identified by `id` and `type`.
  - `ProgressStatusText.SIZE_ESTIMATE` Indicates an estimate for the size of the operation. This will be used exactly once for each operation uniquely identified by `id` and `type`, updating the `` total` `` field.
  - `ProgressStatusText.IN_PROGRESS` Indicates that an operation is in progress. This will be used each time progress occurs, updating the `` totalLoaded` `` and `` currentLoaded` `` fields.
  - `ProgressStatusText.DONE` indicating that an operation has completed.

- **id**: An ID uniquely identifying the object/file being tracked.

- **ok**: A boolean indicating if the operation was succesfull.

- **metadata**: Any additional metadata for the operation being tracked.