In Stranger Things, Hopper knocks in Morse code on the door so that Eleven can know that it's him. It sounded like .. . ... to me which Google tells me is "IES".

Does it actually mean anything or is it just a code that tells her that it's him or did I get the code wrong completely?

Edit: Here the knock in question.

  • It sound to me more like di-dit/dah/di-di-dit which is I·T·S but the only explanation I've found is at ~18:27 in S02E02 where he is detailing the three rules. ' ... Rule no. 2: Only open the door if you hear my secret knock (di-dit/dah/di-di-dit). ...'. However, I agree that with all the focus on Morse Code that it may be a coded message,
    – user62584
    Oct 29, 2017 at 14:15
  • 2
    Seemed to me to just be 2 1 3. It'd be interesting if it meant more than that, but I just took it as a code based on the order & number of knocks.
    – user31178
    Oct 30, 2017 at 14:59
  • 2
    This is definitely not morse code, as the three knocks in the second round of knocking are slower. If you were genuinely trying to message in morse code you would be far more consistent. It seems far more likely that Hopper told Eleven that "you'll know it's me if I knock twice, followed by a break, then knock once, followed by another break and then knock thrice." 2-1-3 as CreationEdge says. Although I've never seen the show.
    – Edlothiad
    Oct 31, 2017 at 11:12
  • 3
    Since both answers were deleted with a note saying they should be comments, without actually posting the comment, two people have suggested that the knock is instead "..-/...", or "US".
    – FuzzyBoots
    Oct 31, 2017 at 11:21
  • 1
    Those rules are pretty much the first things he teaches her, before they would have started on Morse code, so I really don't think it has any actual meaning. It's just a specific sequence of knocks that's 1. easy to remember and 2. unlikely to be used by somebody else by accident. Oct 31, 2017 at 14:33

3 Answers 3


I think it is likely this is just an arbitrary pattern

The main reason is that the SDH says "[knocking rhythmically]", as opposed to "[knocking in morse code]".

However, if we treating the pattern as morse code, we have several options. The pattern is 2-1-3. But the final knock for any section is relatively ambiguous. The possibilities (with their translations) are:

.. . ... (IES)
.- . ... (AES)
.- - ... (ATS)
.. - ... (ITS)
---- ignore for now, this line will be important later ----
.. . ..- (IEU)
.- . ..- (AEU)
.- - ..- (ATU)
.. - ..- (ITU)

(disclaimer: I've never seen this show, so I don't know if any of those letters have significance.)

There are two ways to see if he is trying to do a dit (dot) or dah (dash). The first is timing, and the second is visual.

In morse code, a dit has a length of 1, a dah has a length 3, the space between letters has a length of 1, and the space between words has a length of 3. Acronyms count as a single word, so the only then we need to pay attention to is how long the space is between is letter.

After watching the clip you put in the question, I do not believe there is enough time between letters to allow for a dash. At best the spaces have a length of 2, which is still 2 short of allowing a dash to finish and the space to occur. The observant will notice that it is also too long to count as a dit followed by a space, but let's set that to the side for now.

The other way of guessing the dit/dah nature of the knock is to watch his hand. Does it rest for the possible dahs? Or does it do a quick dit and then wait. Unfortunately this data contradicts what the timing tells us and looks like he is rest his hand on the door after the first and second section of the pattern.

So if we allow for a poor sense of rhythm, and the instinctive nature to rest our hand on the solid surface while "typing" a dah, the best we can say is that he is trying to knock one of the options above the line you ignored earlier.

However, since the various methods contradict, and the second time he knocks was different (in timing) from the first, and the subtitles only say that he is "[knocking rhythmically]", I feel it safe to assume that it was an arbitrary pattern that he picked to be uncommon in nature, thus allowing a reasonable certainty that it was him should Eleven hear the knock.


dot-dot-dash / dot-dot-dot = US

  • 3
    Definitely not it. There's a pause after dot-dot in the first set.
    – sudhanva
    Oct 31, 2017 at 4:08
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    Meta post about this answer and the two deleted answers below it.
    – Rand al'Thor
    Nov 12, 2017 at 12:45

I thought it was dit-dit_dah/dit-dit-dit. Which would be US


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