> ## Documentation Index
> Fetch the complete documentation index at: https://docs.cognite.com/llms.txt
> Use this file to discover all available pages before exploring further.

# About the Cognite OPC Classic extractor

> Read time series and asset information via OPC DA and HDA protocols and stream datapoints to Cognite Data Fusion (CDF).

<Warning>
  The features described in this section are in [public preview](/cdf/product_feature_status#public-preview) and may change.
</Warning>

The extractor copies the OPC hierarchy to CDF, then streams datapoints to time series in CDF. The OPC Classic extractor supports the following:

* **Connecting to multiple OPC servers** over DCOM or COM+.
* **Extracting string and numeric datapoints** from OPC tags.
* **Reading historical data** from OPC HDA, storing progress in a local or remote state store.
* **Starting from a local JSON file** instead of reading the server on each startup, improving performance.