Reference
Competitor backlink gap checker: parameters and reading rules
A gap check compares inlets, not totals. This reference lists the parameters, the order of calls, and what an overlap does and does not tell you.
A gap study asks where rivals have inlets that you lack. In flow terms, it is a comparison of two river systems.
Start with the overlap, because shared inlets are the ones most likely to be a normal feature of your niche. Then look at what sits outside it.
Be careful about the conclusion. A link on a rival's page is a fact about their site, and copying the pattern does not copy the reason for it. Our entry-page method is the better way to see why a source linked.
Parameters you will use
| Parameter | Applies to | Meaning |
|---|---|---|
action | all | Which operation to run, for example intersect |
q | single-domain actions | The domain to look up |
domains | bulk_dr, intersect | Several domains; intersect takes 2 to 10 |
key or Bearer header | paid actions | sk_... key from your account page |
page, per | list actions | Paging; per accepts 10 to 5000 |
sort, order | list actions | Sort column and asc or desc |
Order of operations
Run the overlap first. intersect takes 2 to 10 domains and costs 2 credits, so a first pass over you and nine rivals is $0.0002.
Then take the single-domain actions on the one or two rivals that look most useful. refdomains gives you the sources, anchors shows the words, and toppages shows which of their URLs hold the inlets.
Keep the date of each pull. The index refreshes roughly once a month, so two pulls a week apart will mostly agree, and two pulls a quarter apart will not.
A gap study done in October 2026 is a picture of October 2026. Name the file that way, and you will not mistake it for current data later in the year.
The three-call gap study
Six credits in total, which is $0.0006.
curl "https://linkisflow.com/api.php?action=intersect&domains=you.com,rival-a.com,rival-b.com&key=sk_live_..."
curl "https://linkisflow.com/api.php?action=refdomains&q=rival-a.com&per=1000&key=sk_live_..."
curl "https://linkisflow.com/api.php?action=anchors&q=rival-a.com&key=sk_live_..."How to read what comes back
Overlap is the baseline
Domains that link to several rivals are probably directories, associations or tools your niche shares.
Exclusive inlets are leads
A source that links to one rival only may have a reason you can match, or a relationship you cannot.
Anchors show intent
If a rival's anchors are all commercial phrases, ask whether you want that footprint at all.
Entry pages show structure
Run toppages on both sites and compare which types of page take the links.
We would not export a rival's list and mail every domain on it. Link relationships come from having something worth linking to, and the list only tells you who has linked to similar things before.
Limits of this kind of study
A gap list has blind spots. It cannot see links that were removed before the last refresh. It also cannot see why a source linked. Editorial links, directory listings and paid mentions look alike in a table.
For that reason we use the output as a prompt for reading, not as a to-do list. Open the pages. Judge them as a reader would, and note the ones you would be proud to be listed on. A cost table helps you plan how many of these studies you can afford each month.
If you are comparing against a very large site, remember that DR is a log scale: round(100 · log(ref_domains+1) / log(2·10^7)). Going from 50 to 60 takes far more domains than going from 10 to 20, so compare rivals with that in mind.