Here are the reasons for a discrepancy between what you see in Google SERP and what Ahrefs shows in Site Explorer:
- Timing: Google SERP can change pretty much any minute (or at least every few days). At Ahrefs, we strive for efficient use of our resources, so we currently do not update keywords faster than a few times per day. And we reserve these frequent updates for the most popular keywords. Similarly, we do update the longer tail keywords but at a longer interval, in terms of weeks.
- Location: It's no secret that SERP can be different based on location. We do have IP addresses all around the world, but we do not have them in each city. This can cause some discrepancy in the SERP.
- Personalisation: It's also not a secret that Google serves different results to different people with the goal of helping people get better search results (Read more.) This can be based on things like their search history and browsing patterns. So in some cases for example, your neighbour may get a slightly different SERP for the same keyword and for good reason.
Any of the above 3 reasons or a combination of these can cause a discrepancy between what you see in Google SERP and Ahrefs' Site Explorer.