Glossary · Web analytics
What is unique visitor?
A unique visitor is a distinct person — in practice a distinct browser or device — that visited a website at least once during a given period, counted only once no matter how many pages they viewed or how often they returned.
"Unique" always depends on how the tool recognizes someone it has seen before: a stored identifier, a server-side hash, or a logged-in user id.
Also called: Unique user, Visitor
Updated
How are unique visitors calculated?
Unique visitors = count of distinct visitor identifiers seen in the period
Each browser gets an identifier. With cookie-based tracking it's a random id stored on the device, so the same browser is recognized across days. With cookieless tracking, it's usually a one-way hash of the IP address, user agent and a salt that rotates every day, so the same browser is recognized within a day but counts again the next.
Unique visitors don't add up across periods. Monday's 300 plus Tuesday's 300 is not 600 for the two days if 100 people came both days — the two-day count is 500.
Unique visitor example
In one week, Ana visits your site four times on her laptop and once on her phone; Ben visits once. Your tool reports 3 unique visitors (Ana's laptop, Ana's phone, Ben) and 6 sessions. Unless Ana logs in and you identify her, two devices look like two people.
Why unique visitors matter
Unique visitors measure reach: how many people a launch, a blog post or a campaign actually touched. They're also the right denominator for a visitor-based conversion rate — using pageviews or sessions instead makes the rate look lower the more engaged people are.
Why unique visitor counts differ between tools
- Cookie deletion and browser limits. Safari caps script-set cookies at 7 days, and people clear storage. A returning visitor with a fresh id counts as new.
- Cookieless daily rotation. A hash that changes every 24 hours counts the same person once per day; weekly and monthly totals are higher than cookie-based ones.
- Shared IPs. In cookieless mode, people behind the same office NAT using the same browser version can merge into one visitor.
- Bots and ad blockers. Bot visits inflate the count; blocked scripts deflate it. Tools that filter differently disagree.
- Cross-device behavior. One person on three devices is three unique visitors unless you identify them.
How VisitTrack identifies unique visitors
In standard mode VisitTrack keeps a random anonymous id in a first-party cookie (_vt_vid) on your root domain, so www. and app. share visitors. In cookieless mode nothing is stored on the device; the server derives the id from a hash of the site, IP and user agent with a salt that changes daily, and never stores the IP itself. Hybrid mode does cookieless for visitors in the EU/EEA, UK and Switzerland and standard for everyone else. Visitors flagged as bots are excluded from the count by default.
Frequently asked questions
Is a unique visitor the same as a user?
Not exactly. A unique visitor is an anonymous browser or device; a user is usually a known, logged-in account. One user can appear as several unique visitors across devices until you tie them together with an identify call.
Why are my monthly unique visitors lower than the sum of daily visitors?
Because people who visit on several days are counted once per day in the daily numbers but only once in the monthly total. Unique counts are never additive across periods.
Related terms
- PageviewA pageview is a single load of a page in a visitor's browser, recorded by an analytics tool each time that page is displayed — including reloads and, on single-page apps, each client-side route change.
- SessionA session is a group of pageviews and events from one visitor that happen close together in time, and that ends once the visitor has been inactive for a set timeout — usually 30 minutes.
- Cookieless trackingCookieless tracking is web analytics that counts visitors without storing any identifier on the visitor's device — no cookies, localStorage or similar — typically by deriving a short-lived anonymous id on the server instead.
- First-party vs third-party cookiesA first-party cookie is set by the website you are visiting, under its own domain; a third-party cookie is set by a different domain embedded in that page — such as an ad network or social widget — and can follow you across every site that embeds it.
- User identification (identify)User identification is linking an anonymous visitor in your analytics to a known user in your product — usually with an identify call that sends your own user id and, optionally, traits such as plan or sign-up date.
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