It seems common wisdom that using
meta robots with
robots.txt to block a URL from being indexed "can cause issues", e.g.:
meta robotson a URL is redundant because they are equivalent, and using both
robots.txtand either of the others for a URL can cause issues because
robots.txtblocks crawling, and crawling is required for a bot to even see either of the other ones since they are document-level directives.
However, I cannot see what the "issue" is. Suppose I have a URL
/foo.html for which crawling is blocked using
robots.txt. Then the bot will not crawl the page, but it might still be indexed if
foo.html is followed from another site. However, if we add a
meta robots in
foo.html, indexing will be blocked when the bot reaches the page from another site, independently of what happens to be in
Therefore, while it might be redundant to use both methods, I am not sure why doing so can cause
foo.html to be indexed.