Recovery seed is case sensitive?

[nxvii]

I created a wallet using Electrum for Windows and use the Option to "Extend this seed with custom words."  I used a word with a capital letter.

When I tried to restore this wallet using the Electrum Android app there is no way to enter capital letters, only lowercase.  Does this mean my custom seed will only work on the Windows version?

 

[promise444c5]

I created a wallet using Electrum for Windows and use the Option to "Extend this seed with custom words."  I used a word with a capital letter.

When I tried to restore this wallet using the Electrum Android app there is no way to enter capital letters, only lowercase.  Does this mean my custom seed will only work on the Windows version?

Nope! you can use it on mobile, the reason why  you're  seeing the lowercase is that the keyboard for inputing the seed phrases is inbuilt for  the mobile  app and normally it suppose to be a lower case in the first place.
Hence, if you try same thing on Windows and you entered a correct seedphrase, try changing some of the seed word  to maybe Capitalizing a word/words or changing it to uppercase, it will notify of a valid segwit (if segwit) but it won't support the seed and won't allow you to proceed.

Thus, the custom word is not case sensitive and if you try using that on mobile( you can do this by checking the custom word section below), doing you should be able to access your keyboard and you can choose to use a Uppercase or Lowercase format, so far it's correct the it should accept it .
Check link: https://bitcointalk.org/index.php?topic=5496335.msg64073586#msg64073586.

[BitMaxz]

When I tried to restore this wallet using the Electrum Android app there is no way to enter capital letters, only lowercase.  Does this mean my custom seed will only work on the Windows version?

For the purpose of this thread, I made a wallet today using an uppercase extended word on Electrum PC and imported it to Electrum Mobile to see if typing a lowercase extended word would display the same wallet.

On my PC


On my mobile



After I confirmed all address from the Electrum PC and Electrum mobile are the same. So the extra word even you type it in lowercase or uppercase, the wallet should be the same as what you created from Electrum PC.

[nc50lc]

When I tried to restore this wallet using the Electrum Android app there is no way to enter capital letters, only lowercase.

Which version of Electrum Android app are you using?
Because the latest version (and even the old version) should be able to accept uppercase characters for BIP39 Passphrase compatibility.

Screenshot:


As you can see in the screenshot, you're supposed to scroll-down to type the passphrase below the "Extend seed with custom words" check box.
Your android keyboard app should pop-up, do not use the provided in-app keys which is for your seed phrase above.
Anyways, as mentioned, electrum's seed phrase extension is case-insensitive while BIP39 seed's passphrase is case-sensitive.