Backlink Checker Tools: An Honest Comparison of Ahrefs, Semrush, Moz, and Majestic

← All guides · 10 min read · Published July 2026

TL;DR:

• No backlink checker sees the whole web. Each tool crawls independently, so link counts for the same site routinely differ by 2–3x between tools.
• Ahrefs (DR) is the de facto standard for vetting paid placements; Semrush claims the largest index and bundles a full SEO suite; Moz is the easiest to learn; Majestic is a link-only specialist with the deepest historic archive.
• Free tiers show you a thin top slice — enough for a sanity check, not enough for a full audit.
• Google Search Console is the only source of Google's own link data, but it works only for sites you own.
• For vetting a placement before you pay, the metric stack matters more than the tool: score + organic traffic + outbound link pattern, checked in one consistent index.

What is a backlink checker and how does it work?

Every backlink checker does the same three things: it crawls the web with its own bot, stores the links it discovers in a giant index, and layers proprietary metrics on top so you can judge link strength at a glance. When you type a domain into Ahrefs or Semrush, you're not querying the live web — you're querying that company's snapshot of it.

That's the single most important thing to understand about these tools. The index is the product. A checker can only show you links its crawler has found and kept, which is why the same site can show 4,000 referring domains in one tool and 2,500 in another on the same day. Neither number is "wrong" — they're answers from two different maps of the web.

The second layer is metrics. Each vendor compresses its link data into a 0–100 authority score: Domain Rating (DR) at Ahrefs, Authority Score (AS) at Semrush, Domain Authority (DA) at Moz, and Trust Flow / Citation Flow (TF/CF) at Majestic. None of these numbers comes from Google, and they aren't calibrated to each other — we've broken down the two most-quoted ones in our DR vs DA comparison.

Why do backlink checkers show different numbers?

Because every vendor crawls independently, prioritizes different parts of the web, and prunes dead links on different schedules. Crawl budget goes where each company points it; a link on an obscure forum might be in Majestic's index for years before Ahrefs sees it, or never enter Moz's at all.

The vendors' own index claims illustrate the arms race: Semrush cites a database of 43 trillion backlinks, while Ahrefs' publicly cited figures have been in the tens of trillions. Take all of these with a grain of salt — a bigger raw index isn't automatically better if it's full of dead or spammy URLs, and every vendor counts differently.

Vendor-run comparisons deserve even more skepticism. Semrush's own backlink database study — 10,000 random domains, February 2021 — found Semrush located at least one referring domain for 99.48% of tested URLs and won more head-to-heads than Moz or Majestic. Unsurprising conclusion for a Semrush study. That said, independent testing points the same general direction: a six-month test by Xamsor that seeded fresh test domains with new links found Semrush and Ahrefs substantially out-discovering Moz and Majestic on both volume and speed, with Semrush finding the most links across a 107-site sample. The honest reading: Semrush and Ahrefs currently run the two strongest discovery engines, and everything else trails.

Practical consequence: never compare a metric from one tool against a metric from another, and never judge link growth by switching tools mid-campaign. Pick one index and stay in it — consistency beats coverage. That's also rule one of any backlink analysis.

Ahrefs vs Semrush vs Moz vs Majestic: how do they compare?

Ahrefs

Ahrefs built its reputation on link data, and DR has become the currency of the link building market: sellers price placements by DR, buyers set DR floors, and blacklists get traded in DR terms. Its killer feature for link buyers isn't actually the backlink index — it's that backlink data sits next to organic traffic and keyword estimates for the same domain, in the same report. A site's DR, traffic trend, and outbound link pattern in one screen is exactly what placement vetting needs. Weaknesses: it's expensive, the entry plan meters some reports with credits, and there's no full-product free trial.

Semrush

Semrush claims the largest backlink database of the four and paired it with the broadest toolkit — rank tracking, site audits, PPC data, content tools. Its Backlink Audit module assigns a Toxicity Score, which is useful for triage but shouldn't be treated as Google's opinion — it's a vendor estimate, like every other score here. If you need one subscription for all of SEO rather than a link specialist, Semrush is the rational pick. For pure link work, its interface buries backlink detail a click or two deeper than Ahrefs does.

Moz

Moz's DA is the oldest household-name authority metric, and Moz remains the friendliest tool for people new to SEO — clear UI, good documentation, the lowest entry price of the four, and a genuinely useful Spam Score for fast triage. The trade-off is the index: both the vendor study and independent testing above found Moz discovering fewer links, more slowly, with more stale entries than Semrush or Ahrefs. Fine for tracking your own trend line; a weak foundation for competitive link research.

Majestic

Majestic is the only one of the four that does nothing but links — no keyword tools, no site audits. Its Trust Flow / Citation Flow pair is genuinely different from the others: TF measures proximity to a seed set of trusted sites, so a high-CF/low-TF gap is a classic spam fingerprint. Its Historic Index, built from crawling since the mid-2000s, is unmatched for investigating what a domain used to look like — invaluable when checking whether an "aged" domain spent 2015–2019 as a casino PBN. The interface is dated and its live-link discovery trailed the leaders in testing, which is why Majestic works better as a second opinion than a primary tool.

What free backlink checker options are actually worth using?

Free tiers all share the same design: you get real data from the real index, but only a thin top slice. Useful for a sanity check on a single prospect; useless for a full audit of an established site's profile.

• Google Search Console (Links report). The only place to see Google's own record of who links to you — free, unlimited, but strictly for sites you've verified. Google documents the report in Search Console help. It shows links and anchors but no authority metrics whatsoever.
• Ahrefs Webmaster Tools. Free access to Ahrefs' backlink and audit data for sites you own and verify. The best free option in the list, with the obvious limit that you can't point it at a competitor or a prospect.
• Ahrefs Free Backlink Checker. Point it at any domain and get DR plus a small sample of top backlinks. Enough to see whether a site has any real profile; not enough to vet it.
• Semrush free account. Roughly ten domain lookups per day with truncated result rows. Fine for occasional spot checks.
• Moz free account. A small monthly quota of Link Explorer queries with DA and Spam Score. Enough to screen a handful of prospects per month.

The pattern to notice: free tools are generous with data about your own site and stingy with data about everyone else's. That's deliberate — competitive link data is the product.

Which backlink checker should you use for vetting link placements?

For buying links, use Ahrefs as the primary tool — not because its index always wins discovery tests, but because the whole marketplace prices and negotiates in DR, and because it pairs link data with organic traffic estimates in one view. Here is the five-minute pass we run on every prospect site before it's allowed into a client campaign; it's the tool-level slice of our full backlink quality checklist:

1. DR vs referring domains sanity check. A DR 55 site with 150 referring domains deserves a closer look at who those domains are — inflated scores from a few high-DR links are the classic fake Domain Rating pattern.
2. Organic traffic and its 12-month trend. Score without traffic is the most common trap. A high-DR site with a few hundred monthly organic visits, or a traffic line that fell off a cliff at a known Google update, fails regardless of metrics. (How to read those charts: checking website traffic.)
3. Outbound linked domains. Open the site's outgoing links report. Hundreds of outbound dofollow links to casinos, CBD, and crypto on a "home décor blog" means it's a link farm wearing a costume.
4. Anchor profile. A backlink profile stuffed with exact-match commercial anchors tells you the site sells links carelessly — and that Google has probably noticed.
5. Cross-check one number in a second index. We spot-check suspicious sites in a second tool (Majestic's TF/CF gap or Semrush's traffic estimate). A site that looks strong in one index and invisible in another is a red flag, not a rounding error.

No single metric survives this pass on its own — which is precisely why "DR 50 guaranteed, $30" offers exist. The metrics are cheap to fake individually and expensive to fake together.

Do you need more than one backlink checker?

For most site owners, no — one primary tool used consistently beats three tools used sporadically, both for cost and for trend tracking. The realistic budget answer: Google Search Console (free, always) plus one paid index, with Ahrefs the default if link building is the priority and Semrush the default if you need the full marketing stack.

Agencies and heavy link buyers are the exception. When you're evaluating dozens of prospect sites a month, a second index earns its fee purely as a fraud check, because sellers optimize their sites for whichever single metric buyers screen with. In our own vetting work, the second-index spot check is what catches the sites engineered to look good in exactly one tool.

FAQ

What is the most accurate backlink checker?

None of them is "accurate" against Google, because none sees Google's index. In vendor and independent discovery tests, Semrush and Ahrefs consistently find the most links, with Moz and Majestic trailing. For practical purposes, accuracy matters less than consistency: pick one index and measure trends within it.

Is there a completely free backlink checker?

Yes, with limits. Google Search Console is fully free but only covers sites you own. Ahrefs Webmaster Tools is free for verified sites. For competitor domains, free tiers from Ahrefs, Semrush, and Moz show a small top slice of links — enough for a spot check, not an audit.

Which backlink checker does Google use?

None. Google runs its own crawl and shares a slice of it through Search Console's Links report. Ahrefs, Semrush, Moz, and Majestic are independent companies with independent crawlers, and their authority scores (DR, AS, DA, TF) are proprietary estimates Google doesn't see or use.

Why does Ahrefs show fewer backlinks than Semrush?

Different crawlers, different coverage, different pruning rules. Semrush claims the larger raw index, so higher counts there are common. The gap doesn't mean links are "missing" — each tool reports only what its own crawler has found and kept. Compare trends within one tool instead of counts across tools.

Which backlink checker is best before buying a link?

Ahrefs, because placements are priced in DR and its reports pair link data with organic traffic — the combination that exposes inflated sites. Check DR against referring domains, confirm real and stable traffic, scan outbound links, and spot-check suspicious sites in a second index before paying.

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Don't want to buy two tool subscriptions just to verify a seller's screenshots? We vet every placement in Ahrefs and show you the live DR, traffic, and trend data before you pay a dollar — that's the default on every link building campaign we run, from $69 per link.