Visitors, sessions and pageviews
Three counts are easy to mix up.
- A pageview is one page loaded.
- A session is one visit: a run of pageviews with no long gap.
- A unique visitor is the browser behind the visits, counted once across the period.
If one reader comes on Monday and Thursday, reading three pages each time, that is six pageviews, two sessions and one unique visitor for the week.
How a visitor is recognised
Analytics has to decide that two requests came from the same browser. There are two common ways.
A stored identifier. A script saves a random id in a cookie or in local storage and sends it back on later visits. The same id means the same visitor, across days and weeks. It is accurate for as long as the id survives, and it is the reason many places ask for consent.
A hash. With nothing stored on the device, the tool derives an identifier from what each request already carries, such as the address and the browser's description, mixes in a secret that changes every day, and keeps only the result. The same person gets the same hash during one day, and a new, unrelated one the next. This is how cookieless tracking counts.
Why it is an estimate
No method counts people exactly.
- One person with a phone and a laptop is two visitors.
- Two people behind the same office network and the same browser version can collapse into one under a hash.
- Someone who clears their cookies, or browses in a private window, comes back as a stranger.
- Blockers can stop the script, so those people are not counted at all.
- Bots that pass the filters are counted as visitors.
None of this makes the number useless. The errors are fairly stable from one week to the next, so the trend and the comparisons are meaningful even when the absolute figure is not.
The cost of counting without storage
A daily hash cannot tell that Monday's visitor is Thursday's. In cookieless mode, then, a visitor is new each day and counts are right within a day. Over a week or a month the visitor total will run higher than a tool that stores an id, because returning people are counted again. That is the trade for storing nothing on the device, and it is why the same site shows different visitor totals in different tools.
Reading the number well
Use it for direction. Compare a period with the one before, split it by source, and watch the ratio of conversion rate to visitors rather than the raw count. When two tools disagree, do not average them: pick one and stay with it. The counting rules will differ, and the exact value is rarely what you need to decide.
Try it in trckable
Visitors is the first number on the dashboard. Pick a period and compare it with an earlier one to see whether it moved. Read your dashboard
Related terms
Read more
The newsletter
Notes on measuring what matters.
Occasional emails from Albi: new posts, one chart worth reading, what changed in trckable.
We send one email to confirm your address, and nothing more until you confirm. Every newsletter has a link to leave. What we keep, and who sends it: privacy.