Domain authority checker and site authority checker tools, how to take one reading and why two of them disagree

A domain authority checker is a tool that reads one website address and returns a third party estimate of how strong that whole site looks in the link graph, usually on a 1 to 100 scale. A site authority checker is the same job under a different name. Every one of these tools is reporting its own vendor's score, built from its own crawl of the web, so the number you get depends on which checker you opened. The useful way to use one is to take a reading, write down which tool produced it and on what date, and compare it only with other readings from that same tool.

Google reports 5,400 searches a month in the United Kingdom alone for "domain authority checker" and another 5,400 for "site authority checker", harvested on 22 October 2026 against the United Kingdom target on its own. That is a lot of people opening a checker, and most of them are about to compare two numbers that were never comparable.

What the checkers are actually measuring

None of these scores comes from Google. Each vendor crawls the web, builds its own index of links, and fits a score to what it found. Moz calls its version Domain Authority, Ahrefs calls its version Domain Rating, Semrush calls its version Authority Score, and Majestic splits the idea into Trust Flow and Citation Flow. The full map of which metric belongs to which tool and what each one is built from is set out in what domain authority is in SEO and what it is not. This page is about the reading itself.

So the checker is a window onto one company's index. That single fact explains almost every confusing result people get from these tools.

The three reasons two checkers disagree about the same site

• Different indexes. Each vendor found a different set of linking pages. A site with a lot of links from small British trade publications can score well in a tool that crawls them deeply and modestly in one that does not. Neither number is wrong about the site. They are right about different samples of the web.
• Different scales. These are logarithmic scores, fitted so that very few sites sit near the top. A move from 18 to 28 is a far smaller achievement than a move from 68 to 78, and the gap between two tools is widest in the middle of the range where most real businesses sit.
• Different update clocks. One index refreshes every few days, another on a longer cycle. If you check a site a week after a big piece of coverage, one tool has already counted the new link and the other has not.

The practical rule follows from all three. Pick one tool, check the same site in it every quarter, and read the direction of the line rather than the value. A number compared with itself over time is evidence. Two numbers from two tools placed side by side are two different measurements that happen to share a scale.

Which checker to open, by the job you actually have

There are four distinct jobs behind the single search, and they want different tools.

• One site, one number, right now. Any vendor's own free checker does this. You paste a domain and get the score plus a count of linking domains. This is the ninety second version and it is enough for a sanity check on a site somebody has just offered you a link from.
• A list of sites at once. This is the bulk check, and it is the job free tools cap hardest, because a bulk lookup is the expensive query for the vendor. If you are sorting a prospect list of fifty British sites, find a tool that accepts a pasted list or a file upload and read its daily limit before you start.
• One page rather than one site. Page level scores, Moz's Page Authority among them, answer a different question. A strong site can hold a weak page, and the page is what competes for a query. If you are judging whether you can outrank a specific address, the page level number is the relevant one.
• Trust rather than volume. Majestic's Trust Flow is built to reflect the quality of the neighbourhood a site sits in rather than the quantity of links into it. Trust Flow well below Citation Flow on a site offering you a link is the signal that the link volume came from somewhere thin.

How to take a reading you can defend

A reading is a measurement, so record it like one. Four columns are enough, and the first two are the ones people skip.

Column	Why it is there
The tool, named exactly	The score is meaningless without it, because it belongs to that vendor's index
The date	Indexes move, so a score with no date cannot be checked again
The score, with the linking domain count beside it	The count is the thing underneath the score, and it moves for reasons you can explain
The exact address checked	A domain, a subdomain and a single page are three different readings

That last row is the commonest mistake in the whole exercise. People check the root domain and then talk about a page. Do the same four columns for the three or four sites currently ranking for the query you care about, on the same day and in the same tool. That small table is worth more than any single score, because it tells you whether the gap in front of you is a few links or a different league.

What a reading is good for, and what to do instead of chasing it

These scores do four jobs well. They filter a list of possible link sources quickly. They size up a competitor set before you commit a quarter to a head term. They help spot a domain whose strength looks artificial before you buy it. And tracked over a year in one tool, they show whether your coverage and content work is earning links.

What moves the number is the work underneath it. Publish something worth citing, such as original figures from your own business, a calculator, or a clear explanation in a corner of your market where the existing explanations are poor. Get real coverage with a real angle. Then repair what you already have, because reclaiming unlinked brand mentions and redirecting dead pages that still carry external links is the cheapest link work available to any British business. For the tools that show where those links already point, and exactly where each free tier stops, see the free backlink checkers and where each free tier stops.

Where the authority score belongs in a report

Put it in the appendix, not the headline. A single third party score used as a monthly key performance indicator invites a conversation about the number rather than about the business, and it can fall in a month where you did everything right, because other sites gained links faster. Report non brand organic sessions, qualified enquiries and visibility across your own query set at the top, and keep the authority reading as supporting context with its tool and date attached.

One warning worth passing on. Be wary of any supplier offering a specific authority score as a contractual target. The honest version of that conversation names the tool, names the date it will be measured on, and says what happens when the vendor recalibrates its scale, which vendors do.

Questions about domain and site authority checkers

Is there a genuinely free domain authority checker

Yes. Every major vendor publishes a free single lookup version, and several third party sites wrap a vendor data feed in their own page. The free versions limit how many checks a day you can run and how much of the underlying link data you can see, and that limit is the thing to read before you plan a session of work around one.

What is a good domain authority score

Good is relative to the sites you compete with, not to the scale. Check the four pages currently ranking for your target query in one tool on one day. If they sit a little above you, the query is reachable with content and a handful of links. If they sit far above you, the faster route is the longer and more specific queries first.

Why did my domain authority drop when I changed nothing

Because the score is relative and the index moves. If the vendor's crawl grew, or other sites in the comparison gained links faster than yours, the fitted score can fall while your site is exactly as it was. Look at your linking domain count over the same period. If that held or grew, nothing about your site got worse.

Can I check domain authority for several sites at once

Yes, with a bulk checker that takes a pasted list or an uploaded file. Expect a lower daily allowance than for the single lookup, and check the cap before you paste in two hundred rows, because a bulk run that silently stops halfway is worse than no run at all.

Which is more useful, domain authority or page authority

Page level, when you are deciding whether you can outrank one specific address, because that page is what the query is contested by. Domain level, when you are filtering a long list of possible link sources or sizing up a whole competitor. The two answer different questions, and reporting one as the other is the common error.

Do these scores affect my Google rankings

No. They are third party estimates produced by software vendors, and Google has said repeatedly that it holds no single site wide authority score of this kind. The correlation runs from a genuinely strong site to a high score, so the honest reading is that a rising score reflects work that has already happened.

The checker nobody has opened yet for their own site

There is a second reading now sitting beside this one, and almost no British business has taken it. When a buyer asks ChatGPT, Gemini, Perplexity or Claude who to use for the thing you sell, the assistant writes a few sentences and names two or three companies. It is not picking them off a domain authority table, and the sites it reaches for while building that answer are often not the sites ranking first. So a business can hold a healthy authority score in every tool on this page and still be absent from the answer a buyer actually reads. That reading is worth taking for your own category before somebody else quotes it to you. AI Knows Us puts the buying questions to the main assistants and records which companies get named and which sources each answer was built from.