When someone wants to estimate the traffic of someone else’s domain, the question isn’t just “which tool do I use,” but “how much does it cost me to find out and how much do I trust the data.” The short answer: free alternatives are useful for spotting trends and orders of magnitude; paid ones refine the estimate, but neither replaces the owner’s real data.
What each free route actually measures
Free traffic calculators (Similarweb on its basic plan, browser extensions, Semrush with a query limit, legacy Alexa-type sites) don’t access your server logs or the queried domain’s Google Analytics. They build the figure from user panels, click data from search results, and statistical models. That’s why, on small or niche domains, their figures can deviate a lot.
A typical case from someone who has used these tools daily: you check a local small business’s domain with 300 real monthly visits and the free tool shows “12,000 visits.” The error comes from the model extrapolating from a tiny sample of users who have a certain extension installed. If your website is the one affected, that figure isn’t traffic: it’s statistical noise.
Honest comparison: free versus paid
What the free version does well
- Detecting trends: if a competitor multiplies its traffic fivefold in three months, the free chart usually reflects it even if the absolute figure is inflated.
- Comparing relative market share: when you view several domains in the same sector using the same methodology, the proportion between them is more reliable than the isolated number.
- Seeing the channel breakdown: direct, organic, referrals, and social. The proportions give direction, even if the exact percentages don’t.
What you only get by paying (and even then with caveats)
- Organic keywords with volume and position: paid plans expand the query limit and the historical data.
- Audience and demographic data: estimated age, gender, and interests. Useful for media planning, not for audits.
- Exports and alerts: month-to-month comparisons without cutoffs.
The important caveat: not even the most expensive plan knows the real traffic of someone else’s website. Only the owner, with access to their analytics or server logs, has the exact figure. Any external tool is an estimate.
The route almost no one uses and that is truly free
If the domain is yours, you don’t need estimates: Google Search Console (free) gives you impressions, clicks, CTR, and average position per query; Google Analytics 4 gives you sessions and events, though with the limitation that some traffic is lost to ad blockers and cookie consent. There’s no modeling there: it’s first-hand data.
For someone else’s domain, there’s a legitimate trick: check the public robots.txt and sitemap.xml, and analyze how many indexed URLs the “site:” search shows in Google. It isn’t traffic, but it gives you an idea of the site’s size. If a domain announces 500 articles and Google only indexes 40, the potential organic traffic is much lower than any paid panel suggests.
When neither route works
On websites whose traffic comes mostly from mobile apps, internal traffic, or authenticated sessions, estimation tools fail spectacularly: they don’t crawl apps or private areas. They’re also unreliable for domains with fewer than a thousand monthly visits, because the statistical sample is insufficient. And if what you need is to demonstrate traffic for due diligence, no estimate replaces a screenshot of the Google Analytics property with verified access.
A practical rule for deciding
Use the free version to explore the market and spot anomalies; pay only if you need query volume, extensive historical data, or exports. And always assume a margin of error that, according to the documentation of the measurement platforms themselves, can be significant on low-traffic sites. Promising exact figures about someone else’s traffic is selling smoke.