A:

A file with the OTD file extension is an Octoparse file. It's a file that used to store an Octoparse rule, created by Octoparse developers.

You use Octoparse, a free web scraping tool to make a crawler for collecting data from websites, to make a rule for one web scraping task. By creating a rule in Octoparse, you just point and click the web elements on the web pages and thus Octoparse will generate the rule semi-automatically.

A task in Octoparse contains one web scraping rule, and a rule is stored in one OTD file. 

How To Open an OTD File

Unless you've purposely installed Octoparse to your computer that can open OTD files, then double-clicking on one won't do anything useful. Instead, you MAY need to have Octoparse Client on your computer that can recognize the OTD file.

Octoparse is the only software program used to open an OTD file and edit an OTD file, you can install the Octoparse to open, edit, save, import and export OTD files.

Click HERE to download Octoparse Client.

Check out these tutorials about web scraping with Octoaprse

How Octoparse works to scrape dynamic websites?

How to use Octoparse Smart Mode to scrape websites?