Free browser tool

Platform-dependent character checker

Detect enclosed numbers, Roman numerals, unit symbols, emoji, and other characters that may have compatibility concerns.

Input and settings

How to use it

Scan pasted text for several common character groups that can cause compatibility surprises across systems, fonts or legacy workflows.

Paste the text you want to review.
Select Check.
Review each flagged character, its Unicode code point and the reason it was flagged.

Checks: Enclosed alphanumerics, Roman numerals, enclosed CJK/unit symbols, supplementary-plane characters
Output: Character + Unicode code point + reason
Normal text: Left unchanged and not listed
Scope: Compatibility warning, not a complete character-encoding audit

①, Ⅳ and ㈱ are flagged for different reasons

① is an enclosed alphanumeric, Ⅳ is a Roman numeral, and ㈱ is in the enclosed CJK / compatibility-symbol range.

A clean result does not prove that every target system can display the text. Fonts, database encodings and application-specific restrictions can still matter.

The checker uses Unicode ranges rather than a vendor blacklist

It looks for several broad code-point ranges associated with common compatibility issues instead of trying to identify every problematic character used by every platform.

Emoji and other supplementary-plane characters are included

Characters above U+FFFF are flagged because older systems, fonts or UTF-16 handling can treat them differently from basic multilingual-plane text.

A warning is not the same as “invalid character”

Flagged characters are valid Unicode. The point is to review whether the target environment, file format or recipient can handle them safely.

Final compatibility depends on the destination

A CSV import, old ERP, PDF font and modern browser can all behave differently. Use the list as a preflight check, then test the actual destination when failure would matter.