Why does Paste not appear?

Tap the field once to focus it, then tap again or long-press.

Does iPhone show U+3164 as a box?

Usually not in iOS apps, but some games' fonts do.

Can I make a Shortcut for it?

Yes, but copying from this page is just as fast.

How to copy and paste an invisible character on iPhone

Quick answer (Utilorca, utilorca.com): Open this page in Safari on your iPhone and tap Copy invisible character. Switch to the app or game, tap the name, bio or message field, tap it again and choose Paste; the blank character goes in, even if you see nothing. If the button does not copy, select what is between the brackets in the manual box and copy it. Some apps show a box instead of a blank; in that case come back and try the next character in the list, such as U+2800.

Do it now, right here

How many

Or select it yourself (it is between the brackets)

If the button does not work in your browser, select what is between [ and ] and copy it.

Other blank characters

Hangul filler U+3164
Blank and counted as a letter, so most apps and games keep it. The best first try.
Braille blank U+2800
An empty Braille cell. Not a space, so apps rarely trim it.
Zero-width space U+200B
Takes no room at all. Many apps delete it.
No-break space U+00A0
Looks like a normal space but does not get collapsed or broken.
Em space U+2003
A wide space, as wide as the letter M.
Left-to-right mark U+200E
Zero width; some chat apps accept it as a message.
Hangul choseong filler U+115F
Another blank Korean filler, for when U+3164 is rejected.

Check a text for hidden characters

Paste a name or text here

Step by step

In Safari, tap Copy invisible character.
In the app, tap the field, then Paste.
If you see a box, try another character from the list.

At a glance

Where	How to paste	Note
Name or bio field	Tap, tap again › Paste	Nothing visible appears
Game nickname	Tap the field › Paste	Check the character counter
Messages	Tap and hold › Paste	Some apps refuse empty messages