Backlink Gap
Compare your domain with up to a few competitors and surface the websites that link to them but have never linked to you.
A backlink gap analysis answers a narrow, practical question: which sites already link to businesses like yours, yet do not link to you? Those sites have shown they are willing to reference companies in your space, which makes them far warmer prospects than a cold list built from search operators.
Enter your own domain plus a comma-separated list of competitors. The request opens on app.search.co, which compares the referring domains for each site using DataForSEO's backlink index and returns the domains linking to the competitors that are missing from your profile. Running one comparison requires no account; a free search.co account unlocks any after that.
The value of the output depends almost entirely on which competitors you choose and how you filter the result, so most of this page is about those two steps and about turning a raw gap list into prioritized outreach.
What the gap report shows.
The core output is a list of linking domains that point at one or more of the competitors you entered and do not point at your domain in the index. For each gap domain you can generally see which competitors it links to, which is the most important column in the report, along with index-level context about the domain itself.
Think of the result as a set comparison. If you enter three competitors, a gap domain might link to one of them, two of them, or all three. The more competitors a domain links to, the more it behaves like a general resource for your category rather than a one-off relationship with a single company.
The comparison is only as complete as the index behind it. A domain can appear as a gap even though it links to you, if that link has not been crawled yet. Spot-check a few results before sending outreach to anyone.
Choosing the right competitors to compare.
Your business competitors and your search competitors are often different sites. A national retailer might lose most of its category rankings to a review publisher and two niche specialists, none of which its sales team would name. For gap analysis, use the domains that actually rank for the keywords you want, which you can confirm with the keyword gap tool or by checking the results pages directly.
Avoid mixing very different site types in one run. Comparing a local plumber with a national home improvement magazine produces a gap list dominated by publisher links the plumber will never realistically earn. Group competitors by type: run local peers together, then run publishers separately if content-led links are part of the plan.
Two or three competitors is usually the sweet spot (the tool takes up to three). One competitor gives you that company's relationships; more starts to blur the signal with links that belong to brand size rather than category relevance.
Filtering a gap list into a short list.
A raw gap list for an established category can run to thousands of domains. The fastest filter is overlap: start with domains linking to every competitor you entered, then those linking to all but one. These intersections are where category resources, trade associations and recurring roundups tend to show up.
After overlap, sort by the type of opportunity, because each type needs a different approach. Open the linking page on a sample of each group so you can see how competitors were included.
| Opportunity type | How competitors got the link | Your approach |
|---|---|---|
| Resource or tools page | Listed as a useful provider or tool | Ask for inclusion with a specific reason your page fits the list |
| Roundup or comparison article | Reviewed or ranked alongside peers | Pitch the author for the next update with something new to evaluate |
| Association or membership directory | Paid or earned membership | Decide whether membership is worth it on its own merits |
| News or trade press | Quoted, covered or cited for data | Offer expert commentary or original data, not a link request |
| Partner or integration page | A business relationship | Only pursue if the relationship is real or can become real |
| Sponsorship or event page | Paid sponsorship, usually sponsored | Treat as marketing spend, not link acquisition |
Example: scoping a gap campaign.
These figures are invented to illustrate the process. A B2B software company runs its domain against three search competitors and gets a gap list of 1,800 domains. Of those, 140 link to all three competitors and another 260 link to two.
Reviewing the 140 in full shows roughly a third are software review and listing sites, a quarter are integration partner pages from platforms the company also integrates with, and the remainder are trade publications and a handful of conference sites. The integration pages are the quickest wins, because the relationship already exists and only the listing is missing. The review sites need profiles. The publications become a medium-term digital PR target.
The 1,800 headline number never needed to be worked. A focused list of a few hundred domains, segmented by approach, was the real campaign.
From gap list to outreach.
For each prospect, the competitor link is your research. Read how the page describes the competitor, what format the inclusion took and when it was last updated. A pitch that says "you list three providers, and here is the specific gap our page fills" performs far better than a generic request, and it is only possible because the gap report told you where to look.
Before outreach, verify that the gap is real: run your domain in the referring domains checker or search the linking page for your brand. Then make sure the page you want linked actually deserves the link. If your equivalent resource is thinner than what competitors offer, improve it first, because editors compare.
Where gap analysis goes wrong.
- Copying links that were bought: if a competitor's link sits on a pay-to-play site with no editorial standard, replicating it adds risk, not value.
- Chasing the whole list: working every domain wastes outreach on low-fit sites; intersections and opportunity types should cut the list hard.
- Using business rivals instead of search rivals: the companies you compete with for deals may not be the ones winning the rankings you want.
- Skipping verification: emailing a site that already links to you damages credibility and wastes a contact.
- Ignoring why competitors earned links: many gaps exist because a competitor published data or a tool. The fix there is a comparable asset, not more emails.
Running a backlink gap analysis.
Pick search competitors
Choose three or four domains that rank for your target keywords and are similar in type to your site.
Run the comparison
Enter your domain and the competitors, separated by commas, and open the gap list.
Filter by overlap
Start with domains linking to every competitor, then those linking to all but one.
Segment and verify
Group prospects by opportunity type, confirm each one does not already link to you, and plan the approach for each group.
Backlink gap questions.
How many competitors can I enter?
Why does a site that links to me appear in the gap list?
Is a backlink gap the same as a keyword gap?
Should I try to get every link my competitors have?
Does the tool find the contact person for each site?
Is my first comparison free?
Have a gap list and no time to work it?
SEO.co's link building team turns competitor gap lists into researched, personalized outreach and reports every placement it earns.