DNS
My site shows the old version after I changed DNS. What is going on?
Almost certainly caches. Resolvers keep old answers until the record's TTL expires, and your own computer and browser keep their own copies. Try a private window and a different network, such as your phone off wifi. If those show the new site, it is just a matter of waiting or flushing your local cache. Next time, lower the TTL a day before the change.
What does "propagation" actually mean?
It is the time it takes for caches around the world to expire and fetch your new DNS answer. Nothing is being sent out. See the Host Talk article on the subject for the long version.
What does TTL mean and what value should I use?
TTL is how long, in seconds, a DNS answer may be cached. Something between 300 and 3600 suits most records. Use the low end before a planned change, and the higher end for records that rarely move, to reduce lookups.
Do I need to add a dot at the end of a DNS name?
In a raw zone file, yes, a trailing dot marks a complete name. In most web panels, you do not type it, and the panel adds it. If your record ends up as example.com.example.com, you added the full name where a relative one was expected.
Why can I not put a CNAME on my bare domain?
The root of a domain must also carry NS and SOA records, and a CNAME cannot share a name with other records. Some DNS providers offer ALIAS or flattening records that behave like a CNAME at the root.
How do I check my DNS records from the command line?
Use dig, for example dig example.com A or dig example.com MX. Add @8.8.8.8 to ask a particular resolver. On Windows, nslookup does the same job. Online DNS tools give you the same answers in a browser.
What is the difference between my registrar's DNS and my host's DNS?
DNS is just a service that holds your records. You can use the registrar's, your host's or an independent provider's. What matters is that the nameservers listed at the registrar are the ones where you edit the records.
Is it a problem to have many DNS records?
A few dozen records is routine. Very large zones are fine technically, but each unused record is a potential mistake or takeover risk. Clean out old verification entries and abandoned subdomains.