Controlling Search Engine Crawlers for Better Indexation and Rankings

When should you disallow search engines in your robots.txt file, and when should you use meta robots tags in a page header? What about nofollowing links? In today's Whiteboard Friday, Rand covers these tools and their appropriate use in four situations that SEOs commonly find themselves facing.

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Video transcription

Howdy Moz fans, and welcome to another edition of Whiteboard Friday. This week we're going to talk about controlling search engine crawlers, blocking bots, sending bots where we want, restricting them from where we don't want them to go. We're going to talk a little bit about crawl budget and what you should and shouldn't have indexed.

As a start, what I want to do is discuss the ways in which we can control robots. Those include the three primary ones: robots.txt, meta robots, and—well, the nofollow tag is a little bit less about controlling bots.

There are a few others that we're going to discuss as well, including Webmaster Tools (Search Console) and URL status codes. But let's dive into those first few first.

Robots.txt lives at yoursite.com/robots.txt, it tells crawlers what they should and shouldn't access, it doesn't always get respected by Google and Bing. So a lot of folks when you say, "hey, disallow this," and then you suddenly see those URLs popping up and you're wondering what's going on, look—Google and Bing oftentimes think that they just know better. They think that maybe you've made a mistake, they think "hey, there's a lot of links pointing to this content, there's a lot of people who are visiting and caring about this content, maybe you didn't intend for us to block it." The more specific you get about an individual URL, the better they usually are about respecting it. The less specific, meaning the more you use wildcards or say "everything behind this entire big directory," the worse they are about necessarily believing you.

Meta robots—a little different—that lives in the headers of individual pages, so you can only control a single page with a meta robots tag. That tells the engines whether or not they should keep a page in the index, and whether they should follow the links on that page, and it's usually a lot more respected, because it's at an individual-page level; Google and Bing tend to believe you about the meta robots tag.

And then the nofollow tag, that lives on an individual link on a page. It doesn't tell engines where to crawl or not to crawl. All it's saying is whether you editorially vouch for a page that is being linked to, and whether you want to pass the PageRank and link equity metrics to that page.

Interesting point about meta robots and robots.txt working together (or not working together so well)—many, many folks in the SEO world do this and then get frustrated.

What if, for example, we take a page like "blogtest.html" on our domain and we say "all user agents, you are not allowed to crawl blogtest.html. Okay—that's a good way to keep that page away from being crawled, but just because something is not crawled doesn't necessarily mean it won't be in the search results.

So then we have our SEO folks go, "you know what, let's make doubly sure that doesn't show up in search results; we'll put in the meta robots tag:"

<meta name="robots" content="noindex, follow">

So, "noindex, follow" tells the search engine crawler they can follow the links on the page, but they shouldn't index this particular one.

Then, you go and run a search for "blog test" in this case, and everybody on the team's like "What the heck!? WTF? Why am I seeing this page show up in search results?"

The answer is, you told the engines that they couldn't crawl the page, so they didn't. But they are still putting it in the results. They're actually probably not going to include a meta description; they might have something like "we can't include a meta description because of this site's robots.txt file." The reason it's showing up is because they can't see the noindex; all they see is the disallow.

So, if you want something truly removed, unable to be seen in search results, you can't just disallow a crawler. You have to say meta "noindex" and you have to let them crawl it.

So this creates some complications. Robots.txt can be great if we're trying to save crawl bandwidth, but it isn't necessarily ideal for preventing a page from being shown in the search results. I would not recommend, by the way, that you do what we think Twitter recently tried to do, where they tried to canonicalize www and non-www by saying "Google, don't crawl the www version of twitter.com." What you should be doing is rel canonical-ing or using a 301.

Meta robots—that can allow crawling and link-following while disallowing indexation, which is great, but it requires crawl budget and you can still conserve indexing.

The nofollow tag, generally speaking, is not particularly useful for controlling bots or conserving indexation.

Webmaster Tools (now Google Search Console) has some special things that allow you to restrict access or remove a result from the search results. For example, if you have 404'd something or if you've told them not to crawl something but it's still showing up in there, you can manually say "don't do that." There are a few other crawl protocol things that you can do.

And then URL status codes—these are a valid way to do things, but they're going to obviously change what's going on on your pages, too.

If you're not having a lot of luck using a 404 to remove something, you can use a 410 to permanently remove something from the index. Just be aware that once you use a 410, it can take a long time if you want to get that page re-crawled or re-indexed, and you want to tell the search engines "it's back!" 410 is permanent removal.

301—permanent redirect, we've talked about those here—and 302, temporary redirect.

Now let's jump into a few specific use cases of "what kinds of content should and shouldn't I allow engines to crawl and index" in this next version...

[Rand moves at superhuman speed to erase the board and draw part two of this Whiteboard Friday. Seriously, we showed Roger how fast it was, and even he was impressed.]

Four crawling/indexing problems to solve

So we've got these four big problems that I want to talk about as they relate to crawling and indexing.

1. Content that isn't ready yet

The first one here is around, "If I have content of quality I'm still trying to improve—it's not yet ready for primetime, it's not ready for Google, maybe I have a bunch of products and I only have the descriptions from the manufacturer and I need people to be able to access them, so I'm rewriting the content and creating unique value on those pages... they're just not ready yet—what should I do with those?"

My options around crawling and indexing? If I have a large quantity of those—maybe thousands, tens of thousands, hundreds of thousands—I would probably go the robots.txt route. I'd disallow those pages from being crawled, and then eventually as I get (folder by folder) those sets of URLs ready, I can then allow crawling and maybe even submit them to Google via an XML sitemap.

If I'm talking about a small quantity—a few dozen, a few hundred pages—well, I'd probably just use the meta robots noindex, and then I'd pull that noindex off of those pages as they are made ready for Google's consumption. And then again, I would probably use the XML sitemap and start submitting those once they're ready.

2. Dealing with duplicate or thin content

What about, "Should I noindex, nofollow, or potentially disallow crawling on largely duplicate URLs or thin content?" I've got an example. Let's say I'm an ecommerce shop, I'm selling this nice Star Wars t-shirt which I think is kind of hilarious, so I've got starwarsshirt.html, and it links out to a larger version of an image, and that's an individual HTML page. It links out to different colors, which change the URL of the page, so I have a gray, blue, and black version. Well, these four pages are really all part of this same one, so I wouldn't recommend disallowing crawling on these, and I wouldn't recommend noindexing them. What I would do there is a rel canonical.

Remember, rel canonical is one of those things that can be precluded by disallowing. So, if I were to disallow these from being crawled, Google couldn't see the rel canonical back, so if someone linked to the blue version instead of the default version, now I potentially don't get link credit for that. So what I really want to do is use the rel canonical, allow the indexing, and allow it to be crawled. If you really feel like it, you could also put a meta "noindex, follow" on these pages, but I don't really think that's necessary, and again that might interfere with the rel canonical.

3. Passing link equity without appearing in search results

Number three: "If I want to pass link equity (or at least crawling) through a set of pages without those pages actually appearing in search results—so maybe I have navigational stuff, ways that humans are going to navigate through my pages, but I don't need those appearing in search results—what should I use then?"

What I would say here is, you can use the meta robots to say "don't index the page, but do follow the links that are on that page." That's a pretty nice, handy use case for that.

Do NOT, however, disallow those in robots.txt—many, many folks make this mistake. What happens if you disallow crawling on those, Google can't see the noindex. They don't know that they can follow it. Granted, as we talked about before, sometimes Google doesn't obey the robots.txt, but you can't rely on that behavior. Trust that the disallow in robots.txt will prevent them from crawling. So I would say, the meta robots "noindex, follow" is the way to do this.

4. Search results-type pages

Finally, fourth, "What should I do with search results-type pages?" Google has said many times that they don't like your search results from your own internal engine appearing in their search results, and so this can be a tricky use case.

Sometimes a search result page—a page that lists many types of results that might come from a database of types of content that you've got on your site—could actually be a very good result for a searcher who is looking for a wide variety of content, or who wants to see what you have on offer. Yelp does this: When you say, "I'm looking for restaurants in Seattle, WA," they'll give you what is essentially a list of search results, and Google does want those to appear because that page provides a great result. But you should be doing what Yelp does there, and make the most common or popular individual sets of those search results into category-style pages. A page that provides real, unique value, that's not just a list of search results, that is more of a landing page than a search results page.

However, that being said, if you've got a long tail of these, or if you'd say "hey, our internal search engine, that's really for internal visitors only—it's not useful to have those pages show up in search results, and we don't think we need to make the effort to make those into category landing pages." Then you can use the disallow in robots.txt to prevent those.

Just be cautious here, because I have sometimes seen an over-swinging of the pendulum toward blocking all types of search results, and sometimes that can actually hurt your SEO and your traffic. Sometimes those pages can be really useful to people. So check your analytics, and make sure those aren't valuable pages that should be served up and turned into landing pages. If you're sure, then go ahead and disallow all your search results-style pages. You'll see a lot of sites doing this in their robots.txt file.

That being said, I hope you have some great questions about crawling and indexing, controlling robots, blocking robots, allowing robots, and I'll try and tackle those in the comments below.

We'll look forward to seeing you again next week for another edition of Whiteboard Friday. Take care!