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Bulk Keyword Difficulty (Legacy)
Note that the structure of DataForSEO Labs API requests and responses was updated on 2022-03-19. However, we will continue supporting the legacy version documented here. You can review the documentation of the new version by this link.
 
This endpoint will provide you with the Keyword Difficulty metric for a maximum of 1,000 keywords in one API request. Keyword Difficulty stands for the relative difficulty of ranking in the first top-10 organic results for the related keyword. Keyword Difficulty in DataForSEO API responses indicates the chance of getting in top-10 organic results for a keyword on a logarithmic scale from 0 to 100.  
You can learn more about how we calculate this metric in this help center article.