There are three types of crawling, all of which provide useful data. Internet-wide crawlers are for large-scale link indexing. It's a complicated and often expensive process but, as with social listening, the goal is for SEO experts, business analysts, and entrepreneurs to be able to map how websites link to one another and extrapolate larger SEO trends and growth opportunities. Crawling tools generally do this with automated bots continuously scanning the web. As is the case with most of these SEO tools, many businesses use internal reporting features in tandem with integrated business intelligence (BI) tools to identify even deeper data insights. Ahrefs and Majestic are the two clear leaders in this type of crawling. They have invested more than a decade's worth of time and resources, compiling and indexing millions and billions, respectively, of crawled domains and pages.
A navigational page is a simple page on your site that displays the structure of your website, and usually consists of a hierarchical listing of the pages on your site. Visitors may visit this page if they are having problems finding pages on your site. While search engines will also visit this page, getting good crawl coverage of the pages on your site, it's mainly aimed at human visitors.

* Please note our tool currently assumes Google having 90% of the search market, with Bing + Yahoo! splitting the remaining 10% of the market. Actual market conditions may vary significantly from that due to a variety of factors including: search location, search market demographics, how much marketshare mobile search has relative to desktop in that particular vertical, etc.
Most keyowrd databases consist of a small sample of the overall search universe. This means keyword databases tend to skew more toward commercial terms and the core/head industry terms, with slighlty less coverage of the midtail terms. Many rarely searched for longtail terms are not covered due to database size limitations & lack of commercial data around those terms. Plus if those terms were covered, there would be large sampling errors. Google generates over 2 trillion searches per year and claims 15% of their searches are unique. This means they generate searches for over 300 billion unique keywords each year. The good news about limited tail coverage is it means most any keyword we return data on is a keyword with some commercial value to it. And with Google's Rankbrain algorithm, if you rank well on core industry terms then your pages will often tend to rank well for other related tail keywords.

When it comes down to it, you want to choose a platform or invest in complementary tools that provide a single unified SEO workflow. It begins with keyword research to target optimal keywords and SERP positions for your business, along with SEO recommendations to help your rank. Those recommendations feed naturally into crawing tools, which should give you insight into your website and competitors' sites to then optimize for those targeted opportunities. Once you're ranking on those keywords, vigilant monitoring and rank tracking should help maintain your positions and grow your lead on competitors when it comes to the search positions that matter to your organization's bottom line. Finally, the best tools also tie those key search positions directly to ROI with easy-to-understand metrics, and feed your SEO deliverables and goals right back into your digital marketing strategy.


By 2004, search engines had incorporated a wide range of undisclosed factors in their ranking algorithms to reduce the impact of link manipulation. In June 2007, The New York Times' Saul Hansell stated Google ranks sites using more than 200 different signals.[26] The leading search engines, Google, Bing, and Yahoo, do not disclose the algorithms they use to rank pages. Some SEO practitioners have studied different approaches to search engine optimization, and have shared their personal opinions.[27] Patents related to search engines can provide information to better understand search engines.[28] In 2005, Google began personalizing search results for each user. Depending on their history of previous searches, Google crafted results for logged in users.[29]
Over the past year or two, we've also seen Google begin to fundamentally alter how its search algorithm works. Google, as with many of the tech giants, has begun to bill itself as an artificial intelligence (AI) and machine learning (ML) company rather than as a search company. AI tools will provide a way to spot anomalies in search results and collect insights. In essence, Google is changing what it considers its crown jewels. As the company builds ML into its entire product stack, its core search product has begun to behave a lot differently. This is heating up the cat-and-mouse game of SEO and sending the industry chasing after Google once again.

Difficulty scores are the SEO market's answer to the patchwork state of all the data out there. All five tools we tested stood out because they do offer some version of a difficulty metric, or one holistic 1-100 score of how difficult it would be for your page to rank organically (without paying Google) on a particular keyword. Difficulty scores are inherently subjective, and each tool calculates it uniquely. In general, it incorporates PA, DA, and other factors, including search volume on the keyword, how heavily paid search ads are influencing the results, and how the strong the competition is in each spot on the current search results page.

For traditional SEO, this has meant some loss of key real estate. For SERP results pages that once had 10 positions, it's not uncommon now to see seven organic search results below a Featured Snippet or Quick Answer box. Rather than relying on PageRank algorithm for a specific keyword, Google search queries rely increasingly on ML algorithms and the Google Knowledge Graph to trigger a Quick Answer or pull a description into a snippet atop the SERP.


Think about the words that a user might search for to find a piece of your content. Users who know a lot about the topic might use different keywords in their search queries than someone who is new to the topic. For example, a long-time football fan might search for [fifa], an acronym for the Fédération Internationale de Football Association, while a new fan might use a more general query like [football playoffs]. Anticipating these differences in search behavior and accounting for them while writing your content (using a good mix of keyword phrases) could produce positive results. Google Ads provides a handy Keyword Planner34 that helps you discover new keyword variations and see the approximate search volume for each keyword. Also, Google Search Console provides you with the top search queries your site appears for and the ones that led the most users to your site in the Performance Report35.
This is also where you can see Google's ML algorithms at work. Powered by Google Cloud Platform, the way Quick Answers and Featured Snippets are extracted gets increasingly smarter as Google introduces new innovations in deep learning and neural networks. These constantly evolving algorithms are baked into how the search engine surfaces information.
Robots.txt is not an appropriate or effective way of blocking sensitive or confidential material. It only instructs well-behaved crawlers that the pages are not for them, but it does not prevent your server from delivering those pages to a browser that requests them. One reason is that search engines could still reference the URLs you block (showing just the URL, no title or snippet) if there happen to be links to those URLs somewhere on the Internet (like referrer logs). Also, non-compliant or rogue search engines that don't acknowledge the Robots Exclusion Standard could disobey the instructions of your robots.txt. Finally, a curious user could examine the directories or subdirectories in your robots.txt file and guess the URL of the content that you don't want seen.
Rob Marvin served as PCMag's Associate Features Editor from December 2017 to December 2019. He wrote features, news, and trend stories on all manner of emerging technologies. Beats included: big tech coverage, startups, business and venture capital, blockchain and cryptocurrencies, artificial intelligence, augmented and virtual reality, IoT and aut... See Full Bio
LinkResearchTools makes backlink tracking its core mission and provides a wide swath of backlink analysis tools. LinkResearchTools and Majestic provide the best backlink crawling of this bunch. Aside from these two backlink powerhouses, many of the other tools we tested, such as Ahrefs, Moz Pro, Searchmetrics, SEMrush, and SpyFu, also include solid backlink tracking capabilities.
When Googlebot crawls a page, it should see the page the same way an average user does15. For optimal rendering and indexing, always allow Googlebot access to the JavaScript, CSS, and image files used by your website. If your site's robots.txt file disallows crawling of these assets, it directly harms how well our algorithms render and index your content. This can result in suboptimal rankings.
Another reason is that if you're using an image as a link, the alt text for that image will be treated similarly to the anchor text of a text link. However, we don't recommend using too many images for links in your site's navigation when text links could serve the same purpose. Lastly, optimizing your image filenames and alt text makes it easier for image search projects like Google Image Search to better understand your images.

An SEO expert could probably use a combination of AdWords for the initial data, Google Search Console for website monitoring, and Google Analytics for internal website data. Then the SEO expert can transform and analyze the data using a BI tool. The problem for most business users is that's simply not an effective use of time and resources. These tools exist to take the manual data gathering and granular, piecemeal detective work out of SEO. It's about making a process that's core to modern business success more easily accessible to someone who isn't an SEO consultant or expert.
Rob Marvin served as PCMag's Associate Features Editor from December 2017 to December 2019. He wrote features, news, and trend stories on all manner of emerging technologies. Beats included: big tech coverage, startups, business and venture capital, blockchain and cryptocurrencies, artificial intelligence, augmented and virtual reality, IoT and aut... See Full Bio
That's why PA and DA metrics often vary from tool to tool. Each ad hoc keyword tool we tested came up with slightly different numbers based on what they're pulling from Google and other sources, and how they're doing the calculating. The shortcoming of PA and DA is that, even though they give you a sense of how authoritative a page might be in the eyes of Google, they don't tell you how easy or difficult it will be to position it for a particular keyword. This difficulty is why a third, newer metric is beginning to emerge among the self-service SEO players: difficulty scores.
If you are using Responsive Web Design, use meta name="viewport" tag to tell the browser how to adjust the content. If you use Dynamic Serving, use the Vary HTTP header to signal your changes depending on the user-agent. If you are using separate URLs, signal the relationship between two URLs by tag with rel="canonical" and rel="alternate" elements.
The SEO tools in this roundup provide tremendous digital marketing value for businesses, but it's important not to forget that we're living in Google's world under Google's constantly evolving rules. Oh and don't forget to check the tracking data on Bing now and again, either. Google's the king with over 90 percent of worldwide internet search, according to StatCounter, but the latest ComScore numbers have Bing market share sitting at 23 percent. Navigable news and more useful results pages make Bing a viable choice in the search space as well.
All sites have a home or "root" page, which is usually the most frequented page on the site and the starting place of navigation for many visitors. Unless your site has only a handful of pages, you should think about how visitors will go from a general page (your root page) to a page containing more specific content. Do you have enough pages around a specific topic area that it would make sense to create a page describing these related pages (for example, root page -> related topic listing -> specific topic)? Do you have hundreds of different products that need to be classified under multiple category and subcategory pages?
The tools we tested in this round of reviews were judged on which do the best job of giving you the research-driven investigation tools to identify SEO opportunities ripe for growth, along with offering enterprise-grade functionality at a reasonable price. Whether one of these optimization tools is an ideal fit for your business, or you end up combining more than one for a potent SEO tool suite, this roundup will help you decide what makes the most sense for you. There's a wealth of data out there to give your business an edge and boost pages higher and higher in key search results. Make sure you've got the right SEO tools in place to seize the opportunities.

That's why PA and DA metrics often vary from tool to tool. Each ad hoc keyword tool we tested came up with slightly different numbers based on what they're pulling from Google and other sources, and how they're doing the calculating. The shortcoming of PA and DA is that, even though they give you a sense of how authoritative a page might be in the eyes of Google, they don't tell you how easy or difficult it will be to position it for a particular keyword. This difficulty is why a third, newer metric is beginning to emerge among the self-service SEO players: difficulty scores.
By relying so much on factors such as keyword density which were exclusively within a webmaster's control, early search engines suffered from abuse and ranking manipulation. To provide better results to their users, search engines had to adapt to ensure their results pages showed the most relevant search results, rather than unrelated pages stuffed with numerous keywords by unscrupulous webmasters. This meant moving away from heavy reliance on term density to a more holistic process for scoring semantic signals.[13] Since the success and popularity of a search engine is determined by its ability to produce the most relevant results to any given search, poor quality or irrelevant search results could lead users to find other search sources. Search engines responded by developing more complex ranking algorithms, taking into account additional factors that were more difficult for webmasters to manipulate. In 2005, an annual conference, AIRWeb (Adversarial Information Retrieval on the Web), was created to bring together practitioners and researchers concerned with search engine optimization and related topics.[14]
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