QR-koden henger på veggen.

Because -en is the definite ending for many masculine nouns in Norwegian.
kode means code, and koden means the code.

So:

• en kode = a code
• koden = the code

In this sentence, QR-koden means the QR code.

The hyphen is used because QR is an abbreviation written in capital letters, and Norwegian normally links that kind of element to the noun with a hyphen.

So:

• QR-kode = QR code
• QR-koden = the QR code

This is very common with abbreviations and letter-based words in Norwegian.

In Norwegian, definiteness is often shown by adding an ending to the noun instead of using a separate word like English the.

So English says:

• the wall
• the code

But Norwegian often says:

• veggen = the wall
• koden = the code

That is why you do not need a separate article before QR-koden here.

Henger is the present tense of å henge, which usually means to hang.

In this sentence, it means the QR code is physically attached in a hanging or mounted way on the wall.

So QR-koden henger på veggen is the natural way to say that the QR code is hanging / posted / attached on the wall.

Norwegian often prefers a more specific position verb where English might simply use is.

Compare:

• QR-koden er på veggen = The QR code is on the wall
• QR-koden henger på veggen = The QR code is hanging on the wall

Both can be possible, but henger gives a more concrete picture of how it is placed. Norwegian uses verbs like stå, ligge, and henge much more often than English does.

På means on, and i means in.

If something is attached to the surface of the wall, Norwegian normally uses på veggen:

• et bilde henger på veggen = a picture hangs on the wall

If something is inside the wall, then i veggen could be used:

• et rør er i veggen = a pipe is in the wall

So for a QR code attached to the wall, på veggen is the natural choice.

Because veggen is the definite form: the wall.

• en vegg = a wall
• veggen = the wall

So på veggen means on the wall, not just on wall.

The base forms are:

• en kode = a code
• en vegg = a wall

From those you get the definite forms:

• koden = the code
• veggen = the wall

And in the compound noun:

• QR-kode = QR code
• QR-koden = the QR code

This is the normal Norwegian main-clause word order:

• QR-koden = subject
• henger = verb
• på veggen = place expression

So the structure is basically:

subject + verb + place

If you move the place expression to the front, Norwegian uses verb-second word order:

• På veggen henger QR-koden.

That is still correct, but the verb must stay in second position.

No. In Norwegian, verbs do not change for person the way they do in English.

So the present tense form stays the same:

• jeg henger
• du henger
• den henger
• vi henger

That makes Norwegian verb conjugation simpler than English in this respect.

Yes. Norwegian henger på veggen does not have to mean that the QR code itself is physically dangling by itself. It can refer to a sheet, poster, sign, or label with a QR code on it, as long as it is posted or hanging on the wall.

So the sentence is natural for a QR code displayed on something attached to the wall.

Vegg is the normal everyday word for wall in Bokmål, and veggen is the definite form used here.

You may also see spelling variation in some contexts, especially informal or dialectal forms, but vegg / veggen is the standard form to learn for this sentence.

You would usually say:

• QR-koden hang på veggen. = The QR code hung on the wall.

Here:

• henger = present tense
• hang = past tense

So the sentence changes only in the verb.