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I have traversed through many websites, tutorials, documentations or personal blogs; yet, I couldn't find an exact and clear (scientific) definition (or distinction) of these two:

  • DNS Lookup process
  • DNS Resolution process

My understanding (what I base on the etymology of these words) is, that lookup is the process of giving a domain name, and looking up its respective IP address (or maybe vice versa), whereas resolution is the process of translation from one to another.

Still.. even these two definitions are confusing to me, because, at the end of the day, even if my understanding is correct, lookup would still need a resolution process.. which make these two, effectively synonyms and interchangeable.

Am I confused? or am I correct? or am I missing something important?

Thank you!

Giorgi Tsiklauri
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2 Answers2

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I don't know if there is an explanation with a really strict division between these terms, but I will give you my opinion below.

Overall, these terms are at least largely overlapping if not outright synonymous.

If anything, I think there is a difference in perspective and/or abstraction level.
In my opinion "lookup" feels more suited to the application perspective where you just ask to look something up and get the result back, while "resolution" seems more suited for discussing the whole underlying process to facilitate that.

In practice, as is usually the case with natural language, people will phrase things differently and I would not suggest to read too much into the choice between these very much related terms.

Håkan Lindqvist
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They are synonyms if not even exactly the same thing, specially without any context on their use (the paragraph in which they are used and what is being described)

I would only defer to RCC8499 about DNS terminology that favors resolution (mostly because we have "resolvers", so same root(!)):

Resolver: A program "that extract[s] information from name servers in response to client requests." (Quoted from [RFC1034], Section 2.4) A resolver performs queries for a name, type, and class, and receives responses. The logical function is called "resolution". In practice, the term is usually referring to some specific type of resolver (some of which are defined below), and understanding the use of the term depends on understanding the context.

"lookup" does appear too, but far less.

If I had to really really split them apart, my personal view would be:

  • lookup is closer to request/reply: so you ask a question, you get a reply (or an error). It is one exchange, and it is the "practical" level.
  • resolution is more like the whole process, that could include multiple lookups, to descend the DNS tree from the root. It is more the "theoretical" level, the whole algorithm.

But that is still very fragile and a mostly useless distinction, I would say, between the two words.

However, while we are there:

that lookup is the process of giving a domain name, and looking up its respective IP address

Please don't think that this is the DNS purpose (looking IP addresses), as it is far more than that. Technically a decentralized (or a-centralized) distributed loose coherency database that store various data. Some of them are A and AAAA records for names to IP addresses mapping, but there is far more than that.

Patrick Mevzek
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