Best SEO Software 2021

SEMrush, Ahrefs, Deepcrawl: What’s the difference?

Once you've decided that online search is a priority for your business, it's critical that you find the right software to get the job done. SEMrush, Ahrefs and Deepcrawl is a very popular combination of search tools that digital marketers leverage to help their companies grow.

There is no shortage of seo software. Trying to understand what each tool does, how it's different than others, and which one is the best for your use case is overwhelming. In this article, we'll outline the three primary categories of software created to help digital marketers excel in online search, and recommend our favorite tool in each category. Our goal is that after reading this article, you're able to parse the noisy landscape of search tools and select the best piece of software to for your business.

Note: We assume the audience for this article has a strong foundational knowledge of organic and paid search. If you'd like a refresher on the foundational concepts of each, you can read our article, What is the Difference Between Organic Search and Paid Search?

The three categories of online search tools & our top picks

There are hundreds of tools created to help online marketers with organic and paid search, and it can be hard to force some tools into only one category. However, it's possible to define three primary categories of online search tools, and to sort all tools into these categories based upon what they do best. The three categories of search tools are:

  • Search intelligence tools
  • Backlink software
  • Website crawlers

You'll notice that each software category corresponds to a different component of Google's search technology! Together, they provide a comprehensive set of information that you can leverage to master online search.

  • Search intelligence tools :: Google's search results
  • Backlink software :: Google's map of the Internet
  • Website crawlers :: Google's webcrawler

Search intelligence tools

Search intelligence tools provide data about what's happening in Google's search results. They capture and organize tremendous detail on search engine result pages (SERPs) for millions of daily searches. As you'll read below, this includes valuable insights on everything from keyword search volume & difficulty, keyword ranking by domain, SERP features, ad copy, ads by domain, and more.

These tools are a vital resource for both paid and organic search, and save digital marketers hours of work relative to free or cheap alternatives. Let's take a look at the top use cases for search intelligence tools.

Identifying target keywords

There are many ways to identify target keywords. We'll highlight our two favorite methods that search intelligence tools enable.

Keyword research: Search intelligence tools simply the process of finding promising keywords for you to target through SEO or paid campaigns. Google's Keyword Planner tool is a solid free option to accomplish this, however, it is more time consuming than paid alternatives. The key difference is that paid tools allow you to enter one keyword and see the necessary data for numerous related keywords. This allows you to enter one keyword (e.g. "therapists near me") and instantly see search volume, keyword difficulty, CPCs and more for related keywords (e.g. "therapists in my area", "counselors near me", "therapists", etc.).

Gap analyses: Another highly useful application of search intelligence tools is the ability to compare two or more website domains, and identify keywords that one domain ranks for and the other does not. This analysis can be used to compare your website to your closest competitors and identify keywords you should target through SEO or paid search campaigns.

Keyword position tracking

Another major use case of search intelligence tools is the ability to track the organic search ranking of a basket of your keywords across time. You upload your desired keywords, and the tool pings Google's search API with each keyword each day to capture its ranking. This creates a valuable signal of your SEO performance over time, which you can segment by type of keyword (e.g. branded keyword performance). It is particularly useful for detecting shocks in your organic search performance when Google releases an algorithm change.

Competitive analysis

By recording public data on millions of Google searches each day, search intelligence tools can provide an amazing level of detail on your competitors' marketing programs. With these tools it is possible to see:

  • What keywords your competitors are targeting with paid campaigns
  • The copy they are using in ads over time
  • Images of their display ads

There are many ways to utilize this information. One massive time-saver is the ability to see and learn from the iterations of your competitors ads for specific keywords. If you'd like to begin targeting the same keyword, you can instantly leverage the learning that took your competitor months to uncover. You can also see they keywords and ads that are bringing your competitors the most traffic.

Our search intelligence pick: SEMrush

SEMrush is an extremely popular search tool among digital marketers. As its name suggests, its roots are in search engine marketing. As the tool has matured, it has added features to compete with SEO-first software. The tool offers over 28 features, but the three highlighted above stand out as the most impactful.

SEMrush Pricing
The cost of SEMrush's three plans are below. All prices are for one user:

  • Pro Plan: $119.95 per month
  • Guru Plan: $229.95 per month
  • Business Plan: $449.95 per month

Read our in-depth review of SEMrush, or our guide to SEMrush competitors.

Backlink software

Backlink software crawls the Internet to build and maintain a map of the web's connections. These technologies trace the links connecting billions of websites to build a backlink profile for your website, and conveniently, your competitors' sites.

Backlink profile

One of the most important use cases for backlink software is the ability to get an accurate backlink profile for your website. Backlinks remain a critical component in Google's search algorithm. As a result, monitoring your backlink profile over time is a great KPI for tracking the overall success of your SEO efforts.

Understanding which sites already link to yours is critical to figuring out what backlink campaigns you should run. For example, you might notice that you have 99% backlinks from URLs with very poor authority, or no backlinks from .gov websites. Alternatively, you might realize that you're doing extremely well acquiring backlinks from .edu websites, and that you should double-down on the efforts that helped you acquire those backlinks. Finally, you might realize that you have 100,000 backlinks, but 98% are no follow.

New and lost backlinks

Your new and lost backlinks provide a valuable immediate signal into your SEO performance. For example, you can launch a new backlink campaign and see the number of new backlinks you secured the following day. This fast feedback allows you to iterate backlink campaigns in a timely manner. On the other hand, it's important to quickly detect the loss of quality backlinks. The sooner you detect lost backlinks, the faster you're able to address the root issue.

Best pages by backlinks

Identifying your best performing pages by backlinks is a great way to determine the types of content your team should produce going forward. Additionally, by seeing the websites that have linked to your pages, you can create a list of targets to contact during future backlink campaigns.

Broken backlinks

Fixing broken backlinks is low hanging fruit for improving your backlink profile. It's common to change the URL of a set of pages, or take some pages offline. When this happens, you run the risk of having valuable backlinks no longer point to a valid page on your website. Backlink software helps you identify these broken links, tells you which pages they are pointing to, and allows you to recapture the backlinks you've already worked hard to secure.

Competitive analysis

Similar to search intelligence software, backlink software provides tremendously valuable information on your competitors. You can use these tools to instantly identify your competitors' best performing content in terms of traffic and backlinks. You can also select any page from your competitors' websites and see which other sites backlink to them. These signals are invaluable for shaping your content marketing strategy and backlink outreach programs. You can also see how your competitors backlink profiles are performing over time, which is helpful for understanding the health of their online presence.

Our backlink software pick: Ahrefs

Ahrefs is a leader in online search software and our top choice in this category. The company was founded in 2011, and has spent the past several years building one of the most comprehensive maps of backlinks in the world. In addition to its remarkable dataset, the user-friendly tool makes it easy to pivot from one data view to another. For example, with a few clicks, you can enter a competitive website, find its page with the most backlinks, and see which domains link to that page. Ahrefs also maintains a daily backlink profile ranking for almost all websites across the internet.

Ahrefs Pricing

  • Starts at $99/month
  • Most popular package is $179/month
  • 7 day trial available for $7

To read our in-depth review of Ahrefs click here, or our guide to Ahrefs competitors.

Website crawlers

Website crawlers simulate google-bot, Google's crawler, to help webmasters understand how SEO-friendly their websites are. When deployed on your website, they capture data on the most important on-site SEO factors that you need to rank well in organic search results. We'll go through examples of some major on-site SEO factors below to give you a sense of the value that website crawlers provide.

On-page HTML elements

Getting your on-page HTML elements right is SEO 101, but without close monitoring, it's easy for errors to go undetected. Crawlers will look for missing title tags, H1s, alt tags, canonical tags, meta descriptions, and more. Crawlers will also look for HTML elements that are too short or too long. When the crawler is finished analyzing your pages, it will aggregate all detected errors into a report that is easy to share with your team.

Duplicate pages and content

If you want to confuse google-bot, feed it duplicate pages and content. There are few better ways to hurt your rankings than having two copies of the same page published online without a proper canonical reference. Similarly, having several or hundreds of pages with the same title tags or meta descriptions will also shoot your SEO efforts in the foot. Fortunately, crawlers do an exceptional job detecting duplicate pages and content for you.

Broken internal links

One of the most common SEO issues is broken internal links. No individual likes navigating a site only to discover that a link returns a 404. This is also a big issue for google-bot, as it is wasting its limited time pinging pages that do not exist. Crawlers check the internal links on your site and identify any non-200 status links for remediation.

Improper redirects

It is common to change the URL of pages on your website and redirect users to the new page. However, often times, websites use 302s to redirect traffic. 302s are meant for temporary redirects, and are not recommended for SEO. Ideally, all permanent redirects are 301s. Crawlers will detect this issue and aggregate all errors in a report.

Page speed

Page speed is a critical SEO factor. Crawlers will measure and record the page speed for each page on your website. Leading crawlers will report multiple key metrics: fetch time, load time, and first contentful paint. Identifying which sets of pages on your site are slow is a critical first step in improving your user experience, and your organic search performance.

Mobile and desktop agents

The leading crawlers allow you to crawl your site using desktop and mobile agents. This allows you to simulate Google's desktop and mobile bots so you can detect device-specific errors. This is particularly useful if your website is not mobile-responsive. Even if your site is mobile responsive, this will help you understand the differences in internal linking between your desktop and mobile experiences.

Our website crawler pick: Deepcrawl

Deepcrawl is a highly-popular crawler that allows you to audit your entire website for on-site SEO issues. It analyzes all the key SEO factors outlined above and several more. In addition, the tool's reporting is well-designed, making it easy to digest the results of each crawl. It also saves each crawl and allows you to compare your results over time to measure your on-site SEO progress.

Deepcrawl Pricing

  • Starts at $89 per month for 100,000 pages
  • Enterprise solution requires custom quote


There's hundreds of software tools built to help online marketers with search. The tools come at a wide range of price-points (we didn't even mention enterprise tools like Brightedge or Conductor), and every marketer develops their own preferences over time. In addition, many of the successful tools have significant overlaps in functionality. Please keep this in mind as you evaluate search software tools. For example, despite being our top choices in different categories, there is significant functional overlap between Ahrefs and SEMrush. If you have the budget, it's ideal to have both, but you can certainly get along fine with only one.

We hope that by digging into the three categories of search software, you were able to more clearly understand the distinct sets of functionality you will need to realize your potential as an online marketer and help your business grow. Improving your keyword targeting, strengthening your backlink profile, and optimizing your website for SEO are all critical components in maximizing the value your business can capture from online search.

Bruce Hogan

Bruce Hogan is Co-founder & CEO of SoftwarePundit. He leads the team's research and publishes content about software products and trends. Bruce has experience investing at multi-billion dollar private equity firms, leading teams at venture-backed technology companies, and launching new businesses. You can connect with Bruce on LinkedIn.

Bruce is an expert in several software categories including:

  • Dental software
  • Mental health software
  • SEO software
  • Social media software

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