2

From what I understood, compressed private keys are supposed to represent the same secret key, stored more efficiently thus taking up less space. I assume 'more efficiently' has to do with secp256k1 specifics that I'm not aware of, but I'll take that for granted.

However, when I compare a few compressed and uncompressed private keys:

# example private key
hex: 
85B7DFAB8D2C695C0EBF013AD50A758FDBC62775391B7CE33282634F7DB47480
uncompressed:
5JqBEaUuYJFA4dQsd62ys13RumxCGu97BRu3LzwaVduD8MQnFwc
compressed:
L1heAvnAu97V11iNSHDjyhBiwwQcmB8nH2thMGjtqPsSXKaZ9VwY

# another example private key
hex:
6190289CEB09ED41776AE27AE81F46C6540C56CF8F3900BCAADE96B4470F23D6
uncompressed:
5JZFhabXLayCMCehpyhdCPZ5LXwvgvu3gX4Png4xYzCWYCXJ3jx
compressed:
KzVMt7HNuSw36ARRCmGJmGYa9DbRyEtiqRfyabSUCBToNRwMrAog

# yet another example private key
hex:
763B1998BF7282A99CA21EB821EB9A204589FFA189E290EE64528854FDA91080
uncompressed:
5JiMdW1Czd3tTuy33wiC5wmrkhZxx2PNcC7NVZoFc7AixTVgmf5
compressed:
L1BY471uwL7k9nnL3zUovpkzbt4Vws7kNL37s5m9TxDvBjnadvMy

# etc

I notice that the compressed version (at least the WIF/base58 representation) of a key always seems to be longer. Why's that?

6

Because they are not compressed private keys. They are private keys with a marker that indicates that their corresponding public should be compressed. That extra marker takes an extra byte.

0

by the specification.

they are not "typically longer"

they are "always longer by 1 symbol"

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