>> I don't know if Nutch has a built-in support for this, >> language-detector >> seems to be dedicated only to another task. >You can use the field value added by the language detector to reject the page >from being indexed. Create a custom indexing filter, skipping all documents >you don't need.
Thanks Markus. I'm new to Nutch. I can do that by means of setup files, or you mean it better to write a new plugin ?

