Backlink gap analysis: find the sites that link to your competitors

A backlink gap analysis finds sites that link to your competitors but not to you. Those sites already link to pages like yours, so they are a better starting list for link building than a cold search for "sites in my niche".

This post shows how to run one in Claude, ChatGPT, or Cursor with CalmSEO, how to pick competitors, and how to sort the results into a short list worth contacting. The example uses a real run on our own site, calmseo.com, from November 2026.

How a backlink gap works

You give a backlink tool your domain and one or more competitor domains. It looks up the sites linking to each competitor, keeps the ones that link to all of them, and removes any that already link to you. What is left is the gap.

CalmSEO's find_backlink_gaps tool does this with the DataForSEO Backlinks API, which is built on DataForSEO's own crawled backlink index. Each result row is a linking site with its rank (a 0 to 100 strength score from DataForSEO) and the number of backlinks it has to each competitor. Results are sorted by rank, strongest first.

Step 1. Pick your competitors

The competitors that matter here are the sites that rank for the searches you want, which are not always your business competitors. A quick way to find them is to check who ranks for your main queries:

Use CalmSEO to check the top 10 Google results in the United States for "your main query" and "your second query".
List the domains that appear for both, excluding big sites like Wikipedia, Reddit, and YouTube.

Each SERP check costs 1 credit, about $0.03. A few rules of thumb for the final pick:

• Start with one to three competitors. The tool returns sites that link to every competitor you list, so each extra competitor narrows the list. One competitor gives the broadest and noisiest list. Two or three keep sites that link to several players in your space, which tend to be lists, comparisons, and roundups. The tool accepts up to 20.
• Pick sites close to your size or a little bigger. Very large sites get links from everywhere, so the overlap with them is mostly generic.
• Pick sites with a similar audience. A competitor that serves a different audience brings in links you have no reason to get.

Step 2. Run the gap

Use CalmSEO to find backlink gaps for example.com against competitor-a.com and competitor-b.com.
Return the top 100 linking sites by rank, with the backlink count to each competitor.

Up to 100 rows costs 5 credits, about $0.17. Up to 1,000 rows costs 15 credits, about $0.50. Add dofollow links only to the prompt to count only dofollow links, which drops sites that link to your competitors only with nofollow.

Worked example: calmseo.com

We ran the gap for calmseo.com against two SEO data providers, dataforseo.com and serpapi.com. The tool found 567 sites that link to both and not to us. These were the top five by rank:

This is raw output. We have not vetted these sites, and a high place in the list does not mean a site is a good prospect. A few things the numbers already tell us:

• 567 is too many to review by hand. With two competitors in a crowded space, the list is broad. Adding a third competitor or the dofollow filter would shorten it.
• The top sites link hundreds of times. Each of the top five links to at least one competitor more than 190 times. Counts like 676 or 388 from one site usually mean a sitewide link or a site with many pages that mention the competitor, such as a directory or a docs section. A site with one or two links is more likely an editorial mention in a single article.
• Some counts are lopsided. agricidaniel.github.io links to dataforseo.com 388 times and to serpapi.com twice. A site that heavily favors one competitor may be built around that product, which makes it a weaker prospect for a different one.

Step 3. Qualify the prospects

Rank sorts the list, but it is only one of several checks. Work through the top of the list with these:

Relevance

Does the site cover your topic, and would a link to you make sense to its readers? A relevant site with a modest rank is usually worth more than a strong site on an unrelated topic. To check quickly without leaving the chat, ask the assistant to audit the homepage with audit_page (5 credits, about $0.17), which returns the title, meta description, and H1.

Rank

Rank is DataForSEO's 0 to 100 score based on the links pointing to the site. Use it to compare prospects with each other. It uses its own scale, so do not compare it with scores from other tools.

Spam

The gap results do not include spam scores. For the sites on your shortlist, run a backlink summary, which reports the site's spam score and the average spam score of its own backlinks:

Get a backlink summary for each of these five domains and show their rank, referring domains, and spam scores in one table.

Each summary costs 5 credits, about $0.17, so save this check for the shortlist rather than the whole list.

Dofollow

If you only care about links that pass value, rerun the gap with dofollow links only. A site that disappears from the dofollow run links to at least one of your competitors only with nofollow.

Why they linked

The gap tool returns linking sites, not the linking pages. To see the page, pull the competitor's backlinks and look for the shortlisted domains:

Use CalmSEO to list up to 1,000 backlinks to competitor-a.com, one per linking site.
Find the rows from my shortlisted domains and show the linking page, anchor text, and whether the link is dofollow.

That call costs 15 credits, about $0.50 and covers the competitor's 1,000 strongest linking sites, so it finds the page for prospects in that range. Once you see the page, the reason is usually clear: a tool list, a comparison, a review, a tutorial, or an integration. That reason tells you what to pitch, or whether there is anything to pitch at all.

Step 4. Build the outreach list

CalmSEO does not find contacts or send emails. The assistant can turn the qualified rows into a working list for you:

Make a table of the prospects we kept, with domain, rank, spam score, linking page, why they link to the competitor, and a one-sentence pitch for example.com. Format it as CSV.

Keep the pitch specific to the page that links to your competitor. "You list three tools for X. Here is a fourth that does Y." is a far easier yes than a generic request for a link.

Competitor backlink analysis beyond the gap

The gap shows where competitors have links you lack. Two other checks round out a competitor backlink analysis:

• Compare profiles. Run a backlink summary for you and each competitor to compare referring domains and rank side by side.
• Watch their new links. List a competitor's backlinks sorted by newest to see where they got links recently. It shows where they are getting links now.

Get backlink summaries for example.com, competitor-a.com, and competitor-b.com and compare referring domains, rank, and nofollow share.
Then list the 50 newest backlinks to competitor-a.com and group them by type of site.

What a full run costs

A typical run on CalmSEO: one SERP check to confirm competitors (1), a 100-row gap (5), a 1,000-row competitor backlink list to find linking pages (15), and a page audit plus backlink summary for 5 shortlisted sites (50). That totals 71 credits, about $2.37 at the Lite rate of $10 for 300 credits. New accounts start with 30 free credits, enough for a 100-row gap and a few backlink summaries. Full pricing is on the backlink MCP page.

Limits

• The gap works at the site level and only knows about links in DataForSEO's index, which is smaller than Ahrefs'. Some prospects will be missing, and counts will differ from other tools.
• There is no history. You see the current gap, not how it changed over time.
• A site linking to your competitors does not mean it accepts new links. Qualifying and outreach are still manual work.
• For link building at agency scale, Ahrefs and Semrush have deeper backlink features. See the Ahrefs MCP alternative and Semrush MCP alternative pages for how CalmSEO compares.

To check your own links first, see how to check backlinks. For the full tool list, see the backlink MCP page and the docs.