How can I disallow this URL:
Would these lines in my robots.txt work?
User-agent: * Disallow: /blah/assets* Disallow: /blah/assets/ico/
Both of those would work, but they would also block anything else in those directories. If you only want to block that specific URL, you could do:
Do you have a Google Webmasters Account setup? If so they have a new robots.txt test page where you can see if a URL is blocked or not based on your robots file.
EDIT: My original answer had the below. This would block all URLs that end with favicon.png since it has the $ at the end, but it's pointless in this case since only one favicon.png file can be in that directory. https://support.google.com/webmasters/answer/6062596?hl=en&ref_topic=6061961
Firstly, you shouldn't block your favicon image unless you have a very good reason.
What exactly is the 'blah' supposed to represent in your example? If the URL is as you state in the question, you should just use:
That will prevent crawling of the specific image. To block the whole ico directory, use:
In robots.txt, any path listed matches URLs starting only from the beginning, so the above matches anything beginning with
There is no such thing as a
* wildcard for Disallow in the robots.txt standard. It is a non-standard extension that according to Wikipedia is only supported by Google.