Robots.txt and canonical tag
-
In the SEOmoz post - http://www.seomoz.org/blog/robot-access-indexation-restriction-techniques-avoiding-conflicts, it's being said -
If you have a robots.txt disallow in place for a page, the canonical tag will never be seen.
Does it so happen that if a page is disallowed by robots.txt, spiders DO NOT read the html code ?
-
Thanks Ryan for explaining things very clearly.
-
What we know is there have been many cases where a page that is blocked in robots.txt has appeared in search results. The explanation provided is that robots.txt blocks crawlers during normal site visits, but not necessarily on visits where they are following links from other sites.
-
If spiders follow links to an article on my site, will they read the contents then ? If the canonical tag is on article page itself, will canonical tag will be seen ?
-
Daylan offered a great answer but I would like to add one exception. When crawlers from the major SEs visit your site they will honor your robots.txt file but sometimes they will follow links from other sites to an article on your site, and during that particular visit they will not see the robots.txt file and index your page.
This is one of the reasons why your robots.txt file should be used as minimally as possible, and when it is used you should have a backup process in place such as the canonical or noindex tag on a page.
-
Thanks Daylan for your quick response. I just wanted a second opinion that canonical tag will never be seen if a page is disallowed.
-
Thats correct in most cases:
It works likes this: a robot wants to vists a Web site URL, say http://www.example.com/welcome.html. Before it does so, it firsts checks for http://www.example.com/robots.txt, and finds:
User-agent: *
Disallow: /The "User-agent: *" means this section applies to all robots. The "Disallow: /" tells the robot that it should not visit any pages on the site.
Robots can ignore your /robots.txt. Especially malware robots that scan the web for security vulnerabilities, and email address harvesters used by spammers will pay no attention.
More information available here about:
Got a burning SEO question?
Subscribe to Moz Pro to gain full access to Q&A, answer questions, and ask your own.
Browse Questions
Explore more categories
-
Moz Tools
Chat with the community about the Moz tools.
-
SEO Tactics
Discuss the SEO process with fellow marketers
-
Community
Discuss industry events, jobs, and news!
-
Digital Marketing
Chat about tactics outside of SEO
-
Research & Trends
Dive into research and trends in the search industry.
-
Support
Connect on product support and feature requests.
Related Questions
-
Canonical Tags Before HTTPS MIgration
Hi Guys I previously asked a question that was helpfully answered on this forum, but I have just one last question to ask. I'm migrating a site tomorrow from http to https. My one question is that it was mentioned that I may need to "add canonical tags to the http pages, pointing to their https equivalent prior to putting the server level redirect in place. This is to ensure that you won't be causing yourself issues if the redirect fails for any reason." This is an e-commerce site with a number of links, is there a quick way of doing this? Many Thanks
Technical SEO | | ruislip180 -
Robots.txt Disallow: / in Search Console
Two days ago I found out through search console that my website's Robots.txt has changed to User-agent: *
Technical SEO | | RAN_SEO
Disallow: / When I check the robots.txt in the website it looks fine - I see its blocked just in search console( in the robots.txt tester). when I try to do fetch as google to the homepage I see its blocked. Any ideas why would robots.txt block my website? it was fine until the weekend. before that, in the last 3 months I saw I had blocked resources in the website and I brought back pages with fetch as google. Any ideas?0 -
Is a canonical tag required for already redirecting URLs?
Hi everyone, One of our websites was changed to non-www to www. The non-www pages were then redirected to avoid duplicate issue. Moz and Screaming Frog flagged a number of these redirected pages as missing canonical tags. Is the canonical tag still required for pages already redirecting? Or is it detecting another possible duplicate page that we haven't redirected yet? Also, the rankings for this website isn't improving despite having us optimising these pages as best as we could. I'm wondering if this canonical tag issue may be affecting it. Thank you.
Technical SEO | | nhhernandez0 -
Do you need a canonical tag for search and filter pages?
Hi Moz Community, We've been implementing new canonical tags for our category pages but I have a question about pages that are found via search and our filtering options. Would we still need a canonical tag for pages that show up in search + a filter option if it only lists one page of items? Example below. www.uncommongoods.com/search.html/find/?q=dog&exclusive=1 Thanks!
Technical SEO | | znotes0 -
Robots.txt | any SEO advantage to having one vs not having one?
Neither of my sites has a robots.txt file. I guess I have never been bothered by any particular bot enough to exclude it. Is there any SEO advantage to having one anyways?
Technical SEO | | GregB1230 -
Robots.txt
I have a client who after designer added a robots.txt file has experience continual growth of urls blocked by robots,tx but now urls blocked (1700 aprox urls) has surpassed those indexed (1000). Surely that would mean all current urls are blocked (plus some extra mysterious ones). However pages still listing in Google and traffic being generated from organic search so doesnt look like this is the case apart from the rather alarming webmaster tools report any ideas whats going on here ? cheers dan
Technical SEO | | Dan-Lawrence0 -
'External nofollow' in a robots meta tag? (advertorial links)
I believe this has never worked? It'd be an easy way of preventing any penalties from Google's recent crackdown on paid links via advertorials. When it's not possible to nofollow each external link individually, what are people doing? Nofollowing and/or noindexing the whole page?
Technical SEO | | Alex-Harford0 -
Robots.txt and robots meta
I have an odd situation. I have a CMS that has a global robots.txt which has the generic User-Agent: *
Technical SEO | | Highland
Allow: / I also have one CMS site that needs to not be indexed ever. I've read in various pages (like http://www.jesterwebster.com/robots-txt-vs-meta-tag-which-has-precedence/22 ) that robots.txt always wins over meta, but I have also read that robots.txt indicates spiderability whereas meta can control indexation. I just want the site to not be indexed. Can I leave the robots.txt as is and still put NOINDEX in the robots meta?0