Whenever you type in an address containing a domain name (eg www.linx.ws) the browser must necessarily establish the IP address of the machine on which the corresponding web server is running.
The DNS server (often the one managed by the Internet provider used to connect to the network) which is promptly queried by the browser is useful for immediately establishing which IP address corresponds to the mnemonic address of the type www.linx.ws.
If in its cache the browser does not find any information on the IP associated with the mnemonic address typed by the user in the address bar, this will query one of the DNS servers configured on the system in use (Windows, Linux, Mac OS X ,. ..).
In turn, this DNS first checks for the presence of an entry in its cache. In the event that the name-IP correspondence is found (as happens in most cases), the DNS immediately returns the correct IP to the web browser.
If, on the other hand, the domain name is not present in the cache of the DNS server, this will contact one of the root DNS servers. At this point, once the answer is obtained, the DNS will enrich its cache so that any subsequent requests no longer have to be forwarded to the root server.
The DNS servers that Internet connection providers make available are the ones most frequently used by customers. However, nothing prevents you from exploiting the DNS made available by other providers or by specific companies.
Changing DNS on Android could be useful to overcome certain limitations or to avoid the display on the smartphone or tablet of dangerous, inappropriate, pornographic content, or phishing sites.
Some DNS servers have special “black lists”, continuously updated, which allow you to block attempts to visit directed to websites belonging to the categories just mentioned.

Changing DNS on Android, at least as far as the Wi-Fi connection is concerned, is very simple.
In fact, it is sufficient to access the Android settings, touch the Wi-Fi item, press and hold on the wireless connection in use and then choose Edit config. of network.
Scrolling down the screen, you will find the DNS 1 and DNS 2 boxes. In correspondence with these entries you can type the following IP addresses (these are the IP addresses of the Symantec DNS servers that allow you to block the types of content indicated) :

199.85.126.10, 199.85.127.10 (block malware and phishing)

199.85.126.20, 199.85.127.20 (block malware, phishing and porn sites)

199.85.126.30, 199.85.127.30 (blocks malware, phishing, porn and potentially unsuitable sites)

Keep in mind that the “alternative” DNS servers just specified will be taken into consideration by the browser only for browsing sessions from Wi-Fi connection (but not from 3G / LTE data connection).

Furthermore, the same DNS will only be used by Android browsers that do not use their own data compression mechanisms. In other words, the settings related to DNS servers will be completely ignored if you use, for example, Opera Mini or if you have decided to enable the new Reduce data usage feature of Chrome (see the article Reduce consumption data on Android).
In these cases, in fact, the connection requests are not sent directly to the destination web server but go through the Opera or Google servers that query their DNS, connect to the URL indicated, download the content of the page, compress it. and only then send it to the browser installed on the client-smartphone. After clicking on Save, if you are using – for example – the default browser of Android or Google Chrome (Reduce data usage feature disabled) and you will try to visit a site belonging to one of the categories blocked by the chosen DNS, you should see a screen similar to the following:

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