Backlink Gap: Finding Sites That Link to Competitors but Not You

Semrush’s Backlink Gap tool compares your domain’s backlink profile against competitors’ and lists referring domains that link to them but not to you. It’s the closest thing link building has to a treasure map: sites that link to content in your niche — they haven’t met you yet. The honest caveat: it’s a prospect list, not a link guarantee.

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Key takeaways

Backlink Gap finds proven linkers in your niche — sites already linking to your competitors are the warmest outreach prospects you’ll ever get.
Vet by relevance first, metrics second. A relevant link from a modest site beats an irrelevant link from a giant, every time.
The gap list is a starting point, not a finish line. Every prospect needs a reason to link to you — better content, a new angle, a relationship.
The Link Building Tool is Semrush’s in-platform next step for managing the outreach once you’ve chosen targets.
Start with competitors near your level. Gap analysis against giants produces prospects you can’t realistically win yet.

How Backlink Gap works

You enter your domain and up to a handful of competitor domains. Semrush compares the referring-domain lists and shows the overlap: sites linking to everyone, sites linking to some competitors, and the money view — sites linking to competitors but not to you.

Why is that last group so valuable? Link building’s hardest problem was never finding sites — it was finding sites that actually link to content like yours. Every domain on the gap list has cleared that bar: an editor there already decided your niche was worth linking to. Your job is to give them a reason to link to you too — better content, a new angle, a relationship.

Mechanics worth knowing: it compares referring domains, not individual links (one domain = one row, matching how you should think — relationships, not URLs); you can filter and sort by how many competitors each prospect links to, by authority-style metrics, by link attributes; and the data is only as fresh as the link index — re-run periodically rather than treating one export as permanent. Semrush updates its interface — if a label moved, search Semrush’s help center for the current name.

Setting up the analysis: choosing your competitors

The gap list is only as good as the competitors you feed in.

Pick competitors you can realistically learn from — sites one or two levels above you in the same niche. Enter giants and the list becomes enormous and mostly unwinnable: sites linking to authorities aren’t waiting for your email.

Pick true topical competitors. The tool can’t tell whether a competitor serves your audience. A site sharing a few keywords but serving different readers produces irrelevant prospects. Use the shortlist from your competitor analysis.

Include 3–4 competitors, not one. With one, the list is just “their links minus yours” — noisy. With three or four, prospects linking to multiple competitors rise to the top. A site linking to three rivals is practically raising its hand; one linking to a single competitor might be a fluke or a personal relationship you can’t replicate.

Add one aspirational peer. A site slightly above your weight class — not a giant, but the niche leader you’d like to resemble in a year. Their gap entries are stretch targets: harder to win, worth more when you do.

If you haven’t yet, run your own domain through the Backlink Analytics tutorial first — knowing your profile’s shape keeps your expectations realistic.

Reading the gap results

Start with the multi-competitor prospects. Filter for domains linking to the most competitors but not you — your Tier 1 targets. There are usually fewer than you’d expect, which is good: a short list of warm prospects beats a long list of cold ones.

Then scan the single-competitor links with judgment. Ask of each: is this a type of site that would plausibly link to me? Industry blogs, resource pages, tool directories, niche news — yes. A competitor’s friend’s blog, a client site, a sponsorship — probably not replicable.

Watch for patterns, not just names. Ten gardening blogs linking to competitors is a category insight: gardening bloggers link to this kind of content. Even if you can’t win those exact ten, you know the category to pitch — and hundreds more like them exist. The gap list teaches you where your niche’s links live.

Note the link context. A prospect linking to a competitor’s data study tells you data studies earn links here; one linking to their free tool tells you tools earn links. Match the content type, then build the better version before you pitch.

De-duplicate against your own history. If you’ve pitched a site before — or they already link to you from a page not yet indexed — strike them. Nothing burns goodwill like pitching a site that’s already said yes.

Vetting prospects: relevance first, metrics second

Sort the gap list by the biggest authority number and start at the top? Don’t. A link’s value comes overwhelmingly from relevance, with metrics as a secondary filter. The vetting order:

1. Topical relevance. Open the prospect. Is it in your niche or adjacent? Would your readers plausibly visit it? If not, skip it regardless of metrics — an irrelevant link from a strong domain is at best ignored by search engines, at worst a pattern that looks purchased.

2. Real site, real audience. Genuine content for real readers: recent posts with real dates, an about page with actual humans, signs of engagement. Thin sites with spun content and “write for us” pages selling links are hazards, not prospects.

3. Link context sanity. Where would your link plausibly go? Resource lists, editorial mentions, data citations — natural slots. Author bios of long-closed guest-post programs or sponsored sections — illusions.

4. Metrics last. Now glance at authority-style metrics to prioritize among the relevant, real, sane survivors. A relevant modest site beats an irrelevant giant every time. Metrics order your effort; relevance decides your list.

5. The “would I want this link if search engines didn’t exist?” test. If yes — their audience would genuinely benefit from your content — it’s worth earning. If you only want it for the metric, walk away. Links earned for humans survive algorithm updates; links earned for metrics often don’t.

You’ll typically keep a third to a half of Tier 1 prospects. That’s healthy — a vetted twenty beats an unvetted two hundred.

From prospects to outreach: the honest path

A gap list doesn’t build links; conversations do — and only if you bring something worth linking to.

First, deserve the link. Before emailing anyone, make sure your page is genuinely the best resource on its topic — more complete, more current, clearer, or with original data. If it’s a weaker version of the competitor’s page they already link to, no technique fixes that. The pitch is “we made something better”; without the “something better,” there’s no pitch.

Then find the right person and reason. The editor, the article’s author, the resource-page maintainer — with a reason tied to their content: your updated data improves their article’s accuracy, your guide covers the subtopic their readers ask about. “I wrote something, please link it” is not a reason.

Use Semrush’s Link Building Tool for structure if you want it. It’s the in-platform next step after gap analysis — collecting prospects, finding contacts, tracking outreach in one place. A spreadsheet works too; the discipline matters more than the tool: one prospect, one owner, one status, follow up once, move on.

Expect most to say nothing. Single-digit response rates are normal. Twenty vetted prospects yielding two or three genuine editorial links is a good campaign. Anyone promising more is selling something.

Never pay for links or join link schemes. Buying links, excessive exchanges, and automated blasts violate search engines’ guidelines and can get your site penalized — wiping out far more than the links were worth. The gap list is powerful because it finds earned opportunities. Keep them earned.

Common mistakes

Pitching before the content deserves it. An average page pitched to a great prospect wastes the prospect — you rarely get a second first impression with an editor.

Treating the gap list as a link guarantee. The tool finds prospects. Most will say no or nothing. The list is the beginning of work, not the end.

Chasing only the biggest metrics. The highest-authority prospects are the most pitched and least responsive. Your best ROI is usually the relevant middle tier — big enough to matter, small enough to answer email.

Ignoring why they linked. A prospect linking to a competitor’s original research won’t link to your me-too summary. Match the content type that earned the link, then exceed it.

One-and-done analysis. Competitors earn new links constantly; January’s gap list is stale by June. Re-run quarterly, and review keyword gaps alongside link gaps — the Keyword Gap tutorial plus this workflow give you the full competitive picture in one sitting.

Frequently asked questions

What does Semrush Backlink Gap do?
It compares your domain’s referring domains against up to several competitors’ and shows the overlap — especially the sites linking to competitors but not to you. Those gap prospects are valuable because they’ve already demonstrated willingness to link to content in your niche. You enter your domain plus competitor domains, filter and sort the results, vet each prospect for relevance, and then pursue the real opportunities through outreach.

How many competitors should I add to a Backlink Gap analysis?
Three to four is the sweet spot. With one competitor the list is noisy; with three or four, the prospects linking to multiple competitors rise to the top — and those multi-linker sites are your warmest targets. Choose competitors near your level in the same niche (the shortlist from your competitor analysis), plus optionally one aspirational peer for stretch targets. Avoid giants whose link profiles you can’t realistically replicate yet.

Is a Backlink Gap list a guarantee of getting links?
No — and anyone treating it as one will be disappointed. It’s a prospect list: sites that might link to you if you give them a reason. Every prospect needs vetting (relevance first, metrics second), every outreach needs a genuinely link-worthy page behind it, and most pitches will go unanswered. Twenty vetted prospects yielding two or three editorial links is a realistic good outcome. The tool finds the opportunity; earning the link is still your work.

Should I sort Backlink Gap results by Authority Score?
Not first. Sort first by how many competitors each prospect links to (multi-linkers are warmest), then vet by topical relevance, site quality, and link-context sanity — and only then use authority-style metrics to prioritize among the survivors. A relevant link from a modest site consistently outperforms an irrelevant link from a giant, and the highest-metric prospects are usually the most pitched and least responsive anyway.

What is the Link Building Tool in Semrush?
It’s Semrush’s in-platform workspace for managing outreach after prospecting: collecting link prospects (including from Backlink Gap), finding contact information, sending and tracking outreach emails, and monitoring which prospects convert into links. Think of Backlink Gap as the discovery step and the Link Building Tool as the project-management step. A well-organized spreadsheet works too — the discipline matters more than the tool.

Your concrete next step

Run a Backlink Gap analysis today: your domain plus your three closest competitors. Filter for prospects linking to at least two competitors but not you, and vet the top ten with the relevance-first checklist above. Your goal for this week isn’t twenty links — it’s five genuinely vetted prospects and one page on your site that’s truly worth pitching to them.

Educational note: HowToSemrush publishes independent educational content about using Semrush. This is educational only — not affiliated with or endorsed by Semrush. Semrush updates its features and interface over time, so verify current details on semrush.com.