If you've spent any time researching domain names, you've run into these abbreviations: DA, PA, DR, TF. They show up in appraisal tools, auction listings, and domainer forums constantly, but they're not always explained well.
What exactly do these metrics measure? Who calculates them? And more importantly, how should you actually use them when evaluating a domain to buy or sell?
This guide breaks down each metric clearly, explains where it comes from, and shows you how to read them together, because no single number tells the full story.
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| Domain Metrics Explained |
Why These Metrics Matter for Domain Investors
Domain metrics exist because not all domains are created equal, even if they look similar on the surface. Two five-letter .com domains can have wildly different values depending on their online history, the quality of sites linking to them, and how search engines perceive their authority.
For domainers, these metrics serve two main purposes:
- Buying decisions: quickly filtering out low-quality domains and identifying ones worth a closer look
- Selling strategy: justifying your asking price to buyers who understand SEO
None of these metrics are calculated by Google. Google doesn't publish a public authority score. What DA, DR, and TF measure are third-party estimates of link authority, useful proxies, but not direct signals from search engines themselves.
Important Clarification: Google does not use DA, DR, or TF in its ranking algorithm. These are tools built by Moz, Ahrefs, and Majestic to help SEOs and investors estimate a domain's link strength. They correlate with Google rankings, but they are not Google metrics. {alertWarning}
DA - Domain Authority (by Moz)
Domain Authority is a score developed by Moz that predicts how likely a domain is to rank in search engine results. It runs on a scale of 1 to 100, with higher scores indicating stronger authority. The score is calculated using a machine learning model that factors in the number and quality of inbound links pointing to the domain.
.webp "Domain Authority (by Moz)") |
| Domain Authority (by Moz) |
How it's calculated
Moz looks at the total number of linking domains, the authority of those domains, and the overall link profile structure. It's a relative score, meaning a DA of 40 is only meaningful when compared to other domains. A new domain starts at DA 1. Established sites like Wikipedia or Amazon sit in the high 90s.
If you want to see website Insights on your browser, download MozBar (Moz's free SEO toolbar) for even more convenience. MozBar displays Domain Authority, the number of backlinks, linking root domains, and other essential link metrics directly on your browser. {alertInfo}
What's a good DA for a domain investment?
Its limitations
DA updates roughly once a month, so it can lag behind recent changes to a domain's link profile. It's also sensitive to Moz's own index, if Moz hasn't crawled certain backlinks yet, they won't factor into the score. And because it's logarithmic, it gets progressively harder to improve as you go higher. Moving from DA 20 to 30 is far easier than moving from DA 70 to 80.
When to Use DA: DA is best used as a quick first filter. When scanning a list of expired domains, sort by DA to surface the ones worth investigating further. Don't buy based on DA alone, always dig into the actual backlink profile. {alertInfo}
PA - Page Authority (by Moz)
Page Authority is DA's sibling, also made by Moz, also on a 1–100 scale, but it measures the authority of a specific page rather than an entire domain. Where DA tells you about the domain as a whole, PA tells you how strong a particular URL is.
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| Page Authority (by Moz) |
When it matters for domainers
For most domain investing purposes, DA is more relevant than PA. But PA becomes important in two situations:
- When you're evaluating a domain that had a particularly strong homepage or landing page, the PA of that URL tells you how much link equity was concentrated there
- When you're building or developing a site on an expired domain and want to know which pages inherited the most authority
DA vs. PA - the quick version
Think of it this way: DA is the reputation of the entire building. PA is the reputation of a specific room inside it. For domain investing, you mostly care about the building.
DR - Domain Rating (by Ahrefs)
Domain Rating is Ahrefs' version of a domain authority score. Like DA, it runs from 1 to 100 and measures the strength of a domain's backlink profile. The key difference is that Ahrefs has one of the largest link databases in the industry, which means DR is often considered more comprehensive, and sometimes more accurate, than Moz's DA.
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| Domain Rating (by Ahrefs) |
How it's calculated
Ahrefs calculates DR based on the number of unique domains linking to a site and the DR of those linking domains. It's a recursive system, a link from a high-DR domain passes more value than a link from a low-DR domain. Crucially, Ahrefs focuses on unique referring domains, not raw link count. A thousand links from one domain count far less than links from a thousand different domains.
DA vs. DR - what's the difference in practice?
Both measure link authority, but they use different data sources and different formulas. It's common to see a domain with DA 35 and DR 50, or vice versa. Neither is definitively correct, they're just different perspectives on the same backlink profile. Most experienced domainers check both and look for consistency.
Pro Tip: If a domain has a high DA but a low DR (or vice versa), dig into why. It could mean one tool has indexed links the other hasn't, or it could signal that the backlink profile has issues worth investigating more closely. {alertSuccess}
TF - Trust Flow (by Majestic)
Trust Flow is a metric developed by Majestic that measures the quality and trustworthiness of the links pointing to a domain. Instead of just counting links or estimating authority, TF asks a different question: are the sites linking to this domain actually trusted sources?
Majestic built TF by starting from a seed set of highly trusted websites, think major news outlets, government sites, academic institutions, and measuring how many hops it takes to get from those trusted sources to the domain in question. The closer and more directly a domain is linked to trusted sites, the higher its TF.
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| Trust Flow (by Majestic) |
TF and Citation Flow - always read them together
Majestic pairs TF with Citation Flow (CF), which measures raw link volume regardless of quality. The relationship between the two is what makes TF genuinely useful:
- High TF + High CF = strong, trusted domain with lots of good links - ideal
- High CF + Low TF = lots of links, but low trust - classic spam signal, avoid
- High TF + Low CF = few links, but very high quality - can still be valuable
- Low TF + Low CF = weak domain with little link history - low value
Why TF matters for expired domain research?
TF is one of the best spam filters available for free. A domain with a CF of 40 but a TF of 8 has received a lot of links from low-quality or untrustworthy sources. That's a red flag, whatever authority the domain appears to have on paper is likely artificial and won't transfer real SEO value to a buyer.
Red Flag to Watch: A large gap between Citation Flow and Trust Flow, where CF is much higher than TF, almost always indicates a manipulated or spammy backlink profile. This is one of the clearest warning signs in expired domain research. Walk away. {alertWarning}
Comparing All Four Metrics Side by Side
How to Use These Metrics Together
The biggest mistake beginners make is relying on a single metric. Each one has blind spots. The right approach is to use them as a system:
Step 1: Use DA or DR as your first filter
When scanning a list of expired domains, sort by DA (free, via Moz) or DR (via Ahrefs) to quickly surface domains with meaningful link authority. Set a minimum threshold, DA 20+ or DR 20+ is a reasonable starting point for most investors.
Step 2: Check TF to verify trust
Once you have a shortlist, run each domain through Majestic's free checker and look at TF vs. CF. If TF is at least half of CF (TF/CF ratio of 0.5 or higher), the backlink profile is likely clean. If TF is much lower, the links are suspect.
Step 3: Look at referring domains, not just scores
Open the domain in Ahrefs or Moz and check the actual list of referring domains. How many unique sites are linking? Are they relevant to the domain's niche? Are they real websites with real content, or thin, spammy pages? Ten links from legitimate industry blogs beat a hundred links from random directories every time.
Step 4: Cross-reference with the Wayback Machine
High metrics mean nothing if the domain was previously used for spam, adult content, or link farming. Always check web.archive.org to verify the domain had legitimate use. Clean history + solid metrics = a domain worth paying for.
Quick Evaluation Checklist
- DA or DR above 20 ✓
- TF/CF ratio above 0.5 ✓
- 10+ unique referring domains ✓
- Clean Wayback Machine history ✓
- No trademark conflicts ✓
If all five pass, you have a domain worth serious consideration.
What These Metrics Can't Tell You
As useful as these scores are, they have real limitations that every domainer should understand:
- They don't measure brandability. A domain with DA 15 but a clean, memorable name might sell faster than a DA 40 domain nobody can pronounce.
- They don't reflect Google's actual opinion. Google has its own internal signals that no third-party tool can fully replicate.
- They can be gamed. It's possible to artificially inflate DA or DR through link schemes. High scores from low-quality sources are worse than low scores from clean profiles.
- They lag behind reality. Metrics update on schedules, links gained or lost recently may not be reflected yet.
- They don't capture end-user demand. A domain in a niche with lots of motivated buyers can sell for 10x its "metrics value" because of who wants it, not what the tools say.
Final Thoughts
DA, PA, DR, and TF are tools, not verdicts. Used correctly, they help you filter fast, spot red flags, and make more confident decisions. Used blindly, they'll lead you to overpay for domains with inflated numbers and pass on hidden gems that don't look impressive on paper.
The goal is to build a habit of reading these metrics together, cross-referencing with actual backlink data, and always verifying what the numbers are built on. Over time, that process becomes second nature, and you'll start spotting quality faster than any tool can calculate it.
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