Text that looks right on your screen and wrong on someone else's has almost always hit one of three things: a font without the glyph, a different default for a character that can render as text or emoji, or an app that rewrote your input on save. The characters you sent are usually intact.
Fonts differ, characters do not
Unicode standardises which character a code point is. How it is drawn is entirely up to whichever font the reader's device supplies. Weight, width, and even whether a glyph exists at all vary between platforms, and coverage is thinnest for recent additions and for anything above U+FFFF.
The empty box means a missing glyph
A rectangle, sometimes containing hex digits, means the character is valid and the font has nothing to draw for it. Your text is fine; the device cannot display it. Older phones and minimal system font sets hit this far more often than a current desktop, which is why testing on your own laptop proves very little.
The same character, colour on one device and black on another
Symbols such as ⚠, ☀ and ✉ predate emoji and were later given an emoji presentation alongside their original text form. Which you get depends on the platform default and on whether an invisible variation selector survived the journey. Nothing about your text changed; the rendering decision did.
When the text actually changed
If a name reverts to plain letters after saving, the service rewrote it. Normalisation collapses styled characters back to their plain equivalents by design, and identifier fields often restrict input to a basic character set. This is the one failure mode where the characters really are gone, and retrying will not help.
Narrowing it down quickly
Paste the suspect text into a Unicode lookup: if the code points are what you expect, the problem is rendering, and if they are not, the text was rewritten. Then check on a phone rather than a computer, because that is where font coverage runs out first.
References
Related tools and guides
Last updated September 2026 · Editorial policy · How we verify Unicode claims