There is a scene that keeps repeating: someone compares two websites with a free tool, sees that the competition has “more visits,” and panics. Weeks later they discover that this figure included subdomains of someone else’s marketplace or that half the traffic came from a country where they don’t sell. Choosing a tool without understanding what each one measures is the most expensive mistake in this category.
What you’re really comparing when you check free traffic
Free measurement tools don’t see a site’s internal analytics: they estimate. They combine user panels, installed extensions, ISP data, and statistical models. That means two tools can give figures with differences of 40% for the same website and neither be “wrong” according to its own method. According to the public documentation of several of these services, their estimates are recalibrated periodically, so the history you see today may not match what you saw a year ago.
Before choosing, define what decision you’re going to make with the data:
- Relative size between competitors: a tool with good coverage of your niche is enough.
- Month-to-month evolution: the consistency of the series matters, not the absolute value.
- Traffic source and keywords: you need to see channels and queries, not just the total figure.
- Real traffic to your own domain: here the correct source is your analytics and Search Console, not an external estimator.
Practical comparison of the most-used free options
Semrush (limited plan)
Its strong point is keyword depth and estimation by channel (organic, paid, direct, referral). The free plan gives a reduced number of queries per day, enough to review a handful of domains. Real limitation: on small or highly local niche sites, the sample can be so scarce that the figures become noise. It’s not useful for auditing traffic on a website with fewer than a few hundred monthly visits.
Ahrefs (Webmaster Tools and free tools)
Its organic traffic estimate is usually considered conservative compared to others. The free tools are designed to validate a specific domain, not to do massive analysis. Useful if you want to cross-check a figure that seemed suspicious to you elsewhere.
Similarweb (free version)
It’s the most oriented toward total traffic and channel mix, with audience and geography data. The free version shows ranges and partial data. A detail you only notice by using it: on domains with a lot of app or subdomain traffic, the web figure can end up diluted or aggregated in a confusing way.
Google Trends
It doesn’t give visits, it gives relative interest. It’s the best free option for detecting seasonality and comparing two brands without relying on estimates. Confusing “interest” with “traffic” is a common mistake: a brand can have a lot of search volume and few visits if its SERP is dominated by aggregators.
A specific case that illustrates the problem
When analyzing a local hardware store ecommerce with a free tool, the tool showed high and stable traffic. When cross-checking with server logs and their own analytics, it turned out that a good part of those “visits” were requests from monitoring bots and from a price aggregator that indexed the catalog every hour. The external estimate didn’t distinguish human traffic from crawling. The moral: for your own domain, always validate with first-party data.
What no free tool will tell you
- The competition’s real conversion rate.
- The traffic that comes through private channels (email, WhatsApp, apps).
- The quality of that traffic: a high figure can hide massive bounce.
- The traffic of domains with tracker blocking or paywalls.
No free estimate is an absolute truth. Use them to detect trends and anomalies, cross-check at least two sources, and reserve your own analytics for the decisions that affect your business.