One of the reasons is so that the developers of Internet pages are able to optimize their website accordingly for the individual browsers. This is partly necessary because different browsers have different functions and also react differently to certain queries.

You can see one of the examples on this page here. If you call up this page with Modern browsers, you have the option of entering the IP address into the clipboard at the touch of a button. Older browsers unfortunately do not offer this possibility. Especially in the age of Web 2.0 it is also necessary to know which extensions (plugins) are activated on the system so that, for example, you can use the correct format/plugin for a video stream. Other information is for example to display a website in the right language for the visitor.

These data are not only interesting to optimize a page for certain browsers, but also for extensive statistics. One of the many possibilities is also to track a user on the website (click path) or to determine the geographical distribution of visitors. But of course the information can be used to determine how often a visitor visits a certain page, even if cookie support has been deactivated in the browser. For this purpose, so many values about a visitor are used to generate a unique identifier (hash code). This is helped by the fact that information such as monitor size, installed plugins, browser used, etc. changes relatively rarely.

Sure, it is not necessarily personal data, that the Internet browser releases. Nevertheless, you should be aware of which data can be collected and what possibilities there are in this connection with various databases.

An increasingly interesting topic for the advertising industry is the geographical localization of site visitors in order to display localized advertising for you. This means, for example, that a company can place advertisements especially for Internet surfers from a certain region.

Surely you are wondering how this is technically possible. Most Internet providers dynamically assign users an IP address from their address pool and the browser only passes on the set language identifier to the Internet pages. So how do you get this data?

If only an approximate position of the visitor is required, the IP address is already enough in connection with a database. Even if the IP address is assigned dynamically, it is often the case that providers always select IP addresses from a specific IP pool for a region. Specialised companies such as Maxmind offer extensive databases for free or for a fee, which offer the appropriate geographical information for the IP, such as country, city, region and coordinates. The free databases are usually somewhat less accurate than the paid databases. A check via this method can be completely invisible to the user.

If, on the other hand, a relatively precise position is required, newer Internet browsers offer the option of accessing position data using a GeoLocation interface by JavaScript. These data are usually determined by GPS, mobile radio chip or WiFi interface depending on the end device. If none of these possibilities exists, a database similar to that of Maxmind is used again. The exact procedure for determining the position data depends on the browser and operating system used. In contrast to the own query of a position database, in this case the user of the browser is asked whether the position information may be transmitted.

In the case of determining the position using the IP address, the accuracy depends on how large the regions are in which a provider uses certain IP ranges. The optimal case here is an Internet provider that stores static IP addresses for its customers and possibly also registers them in the customer's name. However, this is usually only the case with Internet access for companies. Here the accuracy is usually very high.

In the case of Internet access with dynamic IP addresses, on the other hand, the accuracy is very variable due to the factors already mentioned. With the database we use, one can roughly say that the actual place of residence is in 80% of the cases within a radius of 25km around the indicated place of residence. In individual cases, however, it can happen that the determined place is completely wrong. This applies in particular to visitors who call up a page via mobile radio (LTE, UTMS, GPRS).

In this context, however, it should also be mentioned that there are much more accurate databases on the market than the Maxmind GeoIP City Lite database we use. It can be said that the accuracy is proportional to the purchase price.

If the position is determined using a GPS chip, mobile radio chip or wlan, the position can now be determined with an accuracy of just a few meters, while IP-based localization is usually several kilometers accurate.

Some network operators now automatically share the location data for IP ranges with the most well-known providers like Maxmind, while others do not. Therefore, providers like Maxmind offer multiple ways to update the IP location data.

If you only want to update individual IPs or IP ranges, you can do this via the following pages:

• Maxmind: https://www.maxmind.com/en/geoip-location-correction
• DbIP: https://db-ip.com/ (enter one of the affected IP addresses at the top right and then search for it. On the results page, there is a "report wrong data" link.

These are just the two providers that we use on our website. There are certainly other IP geolocation providers.

Do you own a network area, possess your own AS, or operate your own data center?

An automatic provision of the data in the form of a Geofeed is recommended here. More information can be found on the Maxmind homepage.

This information contains some general details about the Internet browser and the system configuration. Most of the information is given by Javascript. The exceptions here are browser recognition, referrer and language settings.

Depending on the browser, it is also possible to call up a list of installed plugins. Also interesting about the browser list is that it can be determined with which file the plugin has registered with the browser (dll/so). This can be of interest if you should have problems with a plugin.

The list with the installed fonts is currently determined by Adobe Flash and Javascript. However, there is also the possibility to determine the presence of individual fonts exclusively by Javascript.