Keyword search volume is a rough estimate of demand for a particular query. The primary sources of search volume info are Google Ads (and its API users), Semrush, and Ahrefs. But each of those differs from the others for a given keyword.
Take, for example, the keyword “reddit marketing.” Here’s what each provides for the number of monthly U.S. searches:
- Google Ads: 880,000
- Semrush: 590,000
- Ahrefs: 100,000
The differences stem from where the data comes from and how it’s calculated.
Google Ads Keyword Planner
Google Ads Keyword Planner shows the average monthly searches for each keyword over the preceding 12 months. Thus Google Ads could report a low volume for a newly trending keyword if it wasn’t popular in the previous 11 months.
Moreover, Keyword Planner aggregates search volume for a query among phrases containing the term. For example, the broad-match volume for “pool” includes searches for “swimming pool,” “pool tables,” etcetera — not the single query.
Hence Google Ads’ search volume is often overestimated and inaccurate for a single word or phrase.
Semrush
Semrush’s explanation for its search volume calculations is vague:
Semrush takes sets of data from third-party providers and overlays it with historical clickstream data acquired from reliable sources.
There’s only one conclusion: Semrush is not solely using Google Ads data.
Semrush says an internal 2022 study proves its search volume estimate is the most accurate. The study compared the volume reported by Search Console to that of popular platforms — Semrush, Google Ads, Ahrefs, Moz, more. Semrush’s volume was closest. I’m wary, however, as Search Console shows exact monthly data, whereas search volume reported by those platforms is a 12-month average.
Ahrefs
Ahrefs is also vague in explaining its search volume calculation. Ahrefs cites multiple data sources, including “clickstream” info, a digital record of searches and web activity.
Ahrefs allows customers to download the search volume history for any keyword. One can then blend that keyword and volume with Google Trends to gauge Ahrefs’ accuracy. I did that and received varying results.
In short, keyword search volume is imprecise and inconsistent among the leading sources. Other metrics, such as keyword difficulty and search intent, are also useful when assessing the likelihood of ranking for a word or phrase.
Search volume is only helpful for comparison and keyword sorting — not for estimating the number of clicks for a top ranking. Plus, search results are now fluid with many components. Clicks will likely depend on the query and the results pages it produces.
