Before you pursue a guest post, buy a placement or benchmark yourself against a rival, you need a fast read on how strong each domain is. Marketers overwhelmingly rely on Moz's Domain Authority (DA) score for that judgement, which makes dedicated tools to compare domain authority part of everyday SEO work. Compare properly, and vendor negotiations, partnership shortlists and competitive audits all get sharper.
Quick Answer: Moz Link Explorer is the authoritative source for DA since Moz calculates the metric itself; Semrush Authority Score, Ahrefs' free authority checker and Mangools' SERPChecker provide useful alternative lenses, while bulk DA checkers handle long lists cheaply.
One caution before the reviews: DA is a Moz-created estimate, not something Google uses. Comparing sites with it works because the whole industry reads the same scoreboard — not because Google does.
Choosing a DA Comparison Tool
- Source of the number: for DA specifically, Moz-owned tools are the ground truth; everyone else approximates.
- Multiple domains per view: comparison means side-by-side output, not repeated single lookups.
- Supporting signals: spam indicators and link counts beside the score prevent naive decisions.
- Bulk capability: vetting fifty prospect domains one at a time is a wasted afternoon.
The Shortlist Compared
| Tool | Best For | Free Option |
|---|---|---|
| Moz Link Explorer | Official DA scores and comparisons | Yes, limited monthly queries |
| Semrush Authority Score | Cross-checking with a second metric | Limited free account |
| Ahrefs Website Authority Checker | Free individual lookups (shows DR) | Yes |
| Mangools SERPChecker | Comparing strength within actual SERPs | Trial only |
| Bulk DA checker sites | Screening long prospect lists | Yes, with daily caps |
Individual Breakdowns
Moz Link Explorer and Moz Pro
As the metric's creator, Moz publishes DA straight from its own index. Link Explorer compares several sites at once and pairs the score with linking-domain counts and spam flags. Limitation: Moz's crawl footprint is smaller than Ahrefs', and free usage resets slowly — a handful of queries per month unless you subscribe.
Semrush Authority Score
Semrush blends backlink signals with organic traffic and other inputs into a composite 0–100 score. It is not DA, but running both numbers on the same set of domains exposes outliers — sites whose DA flatters them. Sustained use requires a Semrush subscription.
Ahrefs Website Authority Checker
Free and instant, this checker returns Ahrefs' Domain Rating for any URL. Since DR correlates strongly with DA, it doubles as a zero-cost sanity check when your Moz queries run out. It shows a different metric, so expect small discrepancies against published DA figures.
Mangools SERPChecker
SERPChecker answers the question DA alone cannot: how strong are the domains actually ranking for this keyword? It overlays link-strength metrics on live results, which turns abstract comparisons into context. Access comes through a Mangools trial or subscription rather than a permanent free tier.
Bulk Checker Websites
Free services such as Small SEO Tools and Prepostseo accept pasted lists of dozens of URLs and return DA values in seconds — perfect for first-pass screening. Accuracy depends entirely on which underlying APIs they call, so confirm important verdicts inside Moz itself.
Reading a DA Gap Sensibly
A 15-point difference usually means a genuine hierarchy; a 3-point gap is statistical noise, since the scale compresses near the top. Always pair the score with linking-domain counts and relevance judgements — a niche site at DA 35 often deserves your attention more than a generic news aggregator at DA 55. Remember too that the number only updates when Moz recalculates, so recent changes lag reality by weeks.
Key Takeaways
- Only Moz reports real DA — everything else is a related-but-different score.
- Combine DA with spam signals and relevance; the number alone misleads constantly.
- Bulk checkers accelerate screening, but verify finalists inside Moz Link Explorer.
- Treat small score differences as ties and decide with other evidence.