Unicode Character Inspector

Unicode character inspector

When text behaves unexpectedly — a string length is off by one, a regex misses an accented letter, or an invisible character silently breaks a comparison — the cause is almost always hidden at the code-point level. This inspector splits any text into its individual Unicode code points and shows the U+ hex value, decimal value, and category of each, making invisible and stray characters immediately visible.

Why string length lies in JavaScript (and many other languages)

JavaScript stores strings in UTF-16, where most characters occupy one 16-bit unit. Characters above U+FFFF — the majority of emoji, and some less common scripts — require two 16-bit units called a surrogate pair. The String.length property returns the number of UTF-16 units, not the number of characters a human sees.

For example:

• "A".length → 1 (one code point, one UTF-16 unit)
• "é".length → 1 (one code point, one UTF-16 unit if precomposed)
• "😀".length → 2 (one code point, but two UTF-16 units)

This mismatch causes real bugs: a database column sized for 10 characters can silently truncate an emoji, a regex match can split inside a surrogate pair producing garbage, and .slice() can cut an emoji in half. The inspector’s summary shows both the code-point count and the UTF-16 unit count so you can see the gap immediately.

How the inspector classifies characters

The tool iterates text by code point using JavaScript’s for...of loop (which is surrogate-pair-aware), so each emoji counts as one entry. For each code point it:

1. Reads the code point value with codePointAt(0)
2. Formats it as U+XXXX (padded to 4 or 5 hex digits)
3. Classifies it with Unicode property escapes: \p{L} letter, \p{N} number, \p{P} punctuation, \p{S} symbol, \p{M} combining mark, \p{Z} separator
4. Labels control characters, spaces, tabs, line feeds, and carriage returns explicitly so they become visible

Common debugging scenarios

String length mismatch. Paste the string and compare the code-point count with the UTF-16 unit count in the summary. Any discrepancy indicates astral characters (emoji or rare scripts) that take two units.

Hidden characters. Paste text that refuses to match a known value. The inspector reveals zero-width spaces (U+200B), non-breaking spaces (U+00A0), left-to-right marks (U+200E), and other invisible characters that look like plain spaces but are not.

Combining marks. An accented character can be stored as one precomposed code point (é = U+00E9) or as a base letter plus a combining accent (e + ◌́ = U+0065 U+0301). The inspector shows both as separate rows so you can see whether NFC normalisation is needed.

Copy-paste artefacts. Text copied from PDFs or Word documents often contains smart quotes, soft hyphens (U+00AD), and various punctuation look-alikes. The inspector names each one.

Worked example

Inspecting the string Café — 😀:

Code-point count: 8. UTF-16 unit count: 9. The emoji is the reason.

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