What they actually are
Domain Authority (DA) is a metric from Moz, scored 0–100, meant to predict how well a domain is likely to rank in search results based on its backlink profile. Domain Rating (DR) is Ahrefs' equivalent, also scored 0–100, built from Ahrefs' own backlink index. Neither is published or used by Google. Both are third-party estimates built from each company's own crawl of the web, which is the first thing to understand before treating either as gospel.
How they differ
Both are ultimately backlink-based scores, but they're calculated from different crawl data, updated on different schedules, and use different formulas that each company treats as proprietary. A domain can have a DA of 40 and a DR of 55, or the reverse, without either number being "wrong" — they're just not measuring against the same reference index.
Side-by-side
| Factor | Domain Authority (DA) | Domain Rating (DR) |
|---|---|---|
| Published by | Moz | Ahrefs |
| Scale | 0–100 (logarithmic) | 0–100 (logarithmic) |
| Based on | Moz's own link index | Ahrefs' own link index |
| Used by Google? | No | No |
| Best used for | Relative comparison within Moz's data | Relative comparison within Ahrefs' data |
Why the numbers aren't directly comparable
Because each score depends entirely on that company's own crawl of the web, a site indexed more thoroughly by Ahrefs than Moz (or vice versa) will show different relative scores even if the actual backlink profile is identical. Comparing a DA of 30 on one site to a DR of 30 on another tells you less than comparing DA to DA, or DR to DR, across similar sites using the same tool.
How to actually use them
Both metrics are more useful as a rough, relative filter — "is this site roughly in the same tier as sites I'd expect to link from" — than as a precise measure of quality. They say nothing about topical relevance, which is a bigger factor in whether a link is actually useful. See What Makes a Quality Backlink? for the fuller checklist we actually use.