a backlink gap analysis finds the domains that link to your competitors but not to you. it is the highest-leverage list in link building, because every domain on it already links to your category and you are simply the one they have not found yet. the catch has always been that the feature lives behind a $100+ per month ahrefs or semrush plan. it does not have to. here is how to run one for free in 2026, and exactly where the free path stops and the paid one starts.
what is a backlink gap analysis?
a backlink gap analysis compares the referring domains of two or more competitors against your own and returns the domains that link to them but not to you. ahrefs calls its version link intersect; semrush calls it backlink gap. the underlying idea is identical: a site that links to several of your rivals and not to you is a pre-qualified prospect, because it has already shown it will link to sites exactly like yours.
a domain linking to three of your competitors and not you is worth ten domains that link to only one. the more competitors a site links to, the more it is a category linker and the more obvious your absence is. always rank the gap by overlap first, authority second.
how do you find sites that link to your competitors but not you?
the mechanic is a set subtraction. list every domain linking to each competitor, union those lists, then remove every domain that already links to you. what remains is your gap. the part that turns a raw gap into a usable outreach sheet is ranking: sort by how many competitors each domain links to, then by authority, then strip the platform and cdn noise (think wordpress.com, amazonaws.com, youtube.com) that links to everyone and means nothing.
you can assemble this by hand from any backlink export, or have a tool compute the overlap for you. either way the output you want is a short list where the top rows link to all of your competitors and none of them link to you yet.
the single most useful link-building artifact is a list of domains that link to every competitor you have and not to you. that list is your next month of outreach.
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can you do a backlink gap analysis for free?
yes. the data exists in the open. the common crawl webgraph maps which domains link to which across roughly 120 million domains and 4.4 billion edges, refreshed every quarter. that is enough to compute a real gap without paying for a proprietary index. the free gap-analysis tool runs exactly this: enter your domain and up to three competitors and it returns your top gap domains, already ranked by overlap and authority and with the platform noise filtered out.
the honest limit: free shows you the top of the list, which is usually all a small team needs to start outreach. the full ranked list, csv export, and a public api for scripting the whole thing sit behind a one-time $99 lifetime plan, not a monthly subscription. so the free path covers the actual workflow, and you only pay once if you want the complete export or to automate it.
free vs paid: what you actually give up
the paid suites are not a scam. they buy you a fresher, deeper index and a pile of adjacent features. but for the gap analysis itself, here is the honest trade.
| ahrefs / semrush | free gap analysis | |
|---|---|---|
| gap / link intersect feature | yes, top tier | yes, free |
| price to run a gap | $100+/mo | $0 |
| index freshness | daily-ish | quarterly (common crawl) |
| index depth | very deep | broad, smaller |
| ranked by competitor overlap | ✓ yes | ✓ yes |
| platform / cdn noise filtered | manual | automatic |
| full export + api | metered / credits | $99 once (lifetime) |
| methodology | proprietary | open (common crawl) |
the short version: if you need daily-fresh data on a huge index, pay for a suite. if you need the gap itself, to build a prospect list and run outreach, the free path gets you most of the way and the lifetime plan removes the limits for less than a month of ahrefs.
the free workflow, step by step
whether you do it by hand or with a tool, the steps are the same:
1. pick 2 to 3 real competitors, the ones who rank for the terms you want.
2. pull every referring domain for each of them.
3. remove the domains that already link to you.
4. rank what is left by how many competitors each domain links to, then by authority, and drop the platform and cdn noise.
5. pitch the top of the list first, leading with the fact that they already link to your category.
the only step that is tedious by hand is the overlap and noise filtering at step 4, which is exactly the part a tool should do for you. the rest is judgment and outreach, which no tool can replace.
common questions
is the free data good enough? for finding prospects, yes. you are looking for which domains link to your competitors, not a perfectly current count. a quarterly snapshot of the open web surfaces the same category linkers a paid index does for this use case.
how many competitors should i use? two or three. one competitor gives you a long, weakly-sorted list. three lets you rank by overlap, which is what makes the top of the list genuinely warm.
what do i do with the list? outreach. each prospect already links to sites like yours, so lead with that: name the competitors they link to and give them a specific reason you belong on the same page. reply rates on a gap list beat a cold list because the relevance is built in.
ready to see your own gap? run it free on the gap-analysis tool and start with the domains that link to all of your competitors and none of them link to you yet.
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