DNS: the nervous system of the Internet
The Domain Name System (DNS) is one of the most fundamental protocols of the Internet: it translates human-readable domain names (like google.com) into numeric IP addresses understood by machines (like 142.250.180.46). Without DNS, we would have to remember and type IP addresses for every website — an unthinkable task considering the billions of existing sites. DNS works as a hierarchical database distributed across millions of servers worldwide, with a multi-level caching system that ensures fast responses.
When you type a URL in your browser, the operating system first queries the local DNS cache, then your ISP's resolver, which in turn queries the root servers, the TLD servers (.com, .it, etc.), and finally the domain's authoritative nameservers. This chain of queries, called recursive resolution, happens in just a few milliseconds thanks to caching: each resolver keeps recent responses in memory for the duration of the TTL (Time To Live) specified in the record. Our DNS Lookup performs these queries showing detailed results for each record type.
DNS record types: the complete guide
Each record type serves a specific purpose in the DNS ecosystem. A and AAAA records are the most basic: they map a name to an IP address. The CNAME record creates aliases between names (www points to the main domain). MX records direct mail to the correct mail server — verify them with MX Lookup. TXT records contain free-form text used for email authentication (SPF, DKIM, DMARC) and domain ownership verification. NS and SOA manage zone delegation and authority.
TTL and caching: why DNS changes are not instant
Every DNS record has a TTL (Time To Live) value expressed in seconds that indicates how long resolvers can keep the record in cache. A TTL of 3600 (1 hour) means that after resolving the record, the resolver will use the cached response for one hour before requesting it again. A high TTL (86400, 24 hours) reduces DNS traffic and improves performance, but slows down the propagation of changes. A low TTL (300, 5 minutes) allows rapid updates but generates more DNS traffic.
The optimal strategy is dynamic: use high TTLs (3600-86400) for stable records like NS and MX. Before a planned migration, lower the TTL to 300 seconds at least 24-48 hours in advance (you need to wait for the old TTL to expire). After the migration, verify propagation with DNS Propagation and raise the TTL again once stability is confirmed.
Diagnosing DNS problems
The most common DNS problems and their solutions: the domain does not resolve (verify that A or AAAA records exist and that the nameservers are reachable with NS Lookup), the site shows the wrong content (the A record probably still points to the old IP — check the TTL and wait for propagation), emails are not working (verify MX records and that mail servers are responding), and the SSL certificate shows a domain error (the name in the certificate does not match the resolved hostname).
To diagnose intermittent problems, remember that different resolvers may have different versions in cache. A user in Italy might see the old IP while one in the USA sees the new one, depending on when each resolver last updated its cache. The DNS Propagation Checker queries servers around the world showing which response each one returns, allowing you to identify geographic inconsistencies.
A subtle but frequent error is having a CNAME record on the domain root (apex). DNS specifications prohibit a CNAME where other records exist (and the root always has SOA and NS). Many DNS providers offer alternative records called ALIAS, ANAME, or CNAME flattening that resolve the CNAME server-side and return an A record to the resolver. If your site is on a CDN or PaaS and you need to point the domain root, use these CNAME alternatives.