Several references to the quote "There are only two hard things in Computer Science: cache invalidation and naming things" can be found, such as Martin Fowler's blog and others.

I'm unable to find the source of this quote, has he ever said it?


2 Answers 2


As his only son, and colleague with him at Netscape from 95-97, I can attest that my dad did indeed throw that quote around, on more than one occasion. I'm fairly confident that he originated it (he was fond of coming up with clever quippets), though I haven't been able to figure out how it disseminated so widely over the past couple of decades. I'll keep looking around in old web archives and mails to see if I can dig something up.

Reference from David Karlton's personal blog at karlton.org: https://www.karlton.org/2017/12/naming-things-hard/

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    Welcome to Skeptics! It is always exciting when someone directly involved in an issue graces us with an answer, but unfortunately there are so many trolls on the Internet, we can't accept an anecdote at face value. If you can find a reference in an old web archive, or link to somewhere where you say this and we can verify who you are, that would be fantastic. Thanks!
    – Oddthinking
    Commented Aug 11, 2017 at 2:38
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    If you'd like to share this anecdote on a blog or other website of yours, then that website can be quoted and used as a reference for your answer here. Plus, it'd have the added advantage of sharing the information more broadly!
    – Nat
    Commented Jan 29, 2018 at 1:16
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    How can I cite it in a paper I'm writing?
    – Shamoon
    Commented May 30, 2019 at 13:10
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    I was going to say that we should add "identity verification" to the original list of things that are hard, but I suppose this can fall under "naming things". :-) Commented Apr 29, 2020 at 2:22
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    @Oddthinking, would this count as a reference even if it is recent? karlton.org/2017/12/naming-things-hard
    – Murven
    Commented Jul 10, 2020 at 21:01

Tim Bray says on Twitter:

Phil [Karlton] said it, I reported it, someone else added on the “off-by-one”.

Leon Bambrick replies that he added off-by-one.

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    I'd like a little bit more than just one person saying he "reported it". Where did he report it? I found only tbray.org/ongoing/When/200x/2005/12/23/UPI which is dated 2005 but a google search for "cache invalidation and naming things" returns random results as far back as February 2001. Commented Jan 21, 2015 at 21:27
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    I don't remember who added the "off-by-one errors" but I attest that I added the second "cache invalidation." There are only two hard things in Computer Science; cache invalidation and naming things and one-off errors and cache invalidation Commented Feb 16, 2023 at 22:09

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