Unicode, ASCII & Emoji Terms: The Complete Glossary

The single standard that assigns every letter, symbol, and emoji a unique number, so any device can display text the same way regardless of language or platform. Before Unicode, computers used dozens of incompatible encodings, which is why old text files sometimes turn into garbled boxes today.

One single unit of text — a letter, digit, punctuation mark, or symbol. Most characters are one Unicode code point, though a few, mainly emoji, are built from more than one.

A single assigned number inside Unicode’s space, written like U+0041 for a capital A. Unicode has room for 1,114,111 possible code points; only 159,801 are assigned as of Unicode 17.0.

A much older, much smaller standard from 1963 that only covers 128 characters — the basic English alphabet, digits, and a handful of symbols. Unicode was built to include ASCII as a subset, so plain English text looks identical in both.

The most common way of storing Unicode characters as actual bytes on disk or over a network. It represents plain ASCII text using exactly one byte per character, and uses more bytes only for characters outside that basic range — which is why UTF-8 became the web’s default encoding.

The fixed-size chunk a particular encoding uses to store one piece of a character. UTF-16, used internally by many platforms, measures text in 16-bit code units — which is exactly why some emoji “count” as 2 characters on platforms like X, even though they look like one symbol.

A writing system, like Latin, Cyrillic, Arabic, Devanagari, or Han — not a single language. Unicode supports 172 scripts, and several unrelated languages often share the same script.

One of 17 large blocks that divide Unicode’s entire codespace, numbered 0 to 16. Plane 0, the Basic Multilingual Plane, holds almost every character in everyday use; later planes hold rarer scripts, historic characters, and most emoji.

A named, contiguous range of code points grouping related characters, such as “Mathematical Alphanumeric Symbols” or “Egyptian Hieroglyphs.” Unicode 17.0 defines 346 blocks.

The actual visual shape a font draws for a character. The same code point can look different across fonts — a glyph is the drawing, the code point is the identity underneath it.

A special character that attaches to the character before it rather than standing alone, usually an accent mark or diacritic. Stack enough combining characters onto one letter and you get the distorted “zalgo” text effect our Cursed Text Generator produces.

A workaround used by UTF-16 to represent characters outside its normal 16-bit range, by combining two special code units together. Most emoji above the Basic Multilingual Plane need a surrogate pair, which is part of why they can silently cost more than one “character” in a length count.

A pictograph character recommended by the Unicode Consortium for use as a small, colorful symbol rather than plain text. There are 3,953 emoji in Unicode 17.0, spanning 10 official categories.

Several code points combined into what displays as one single emoji — a flag, a family, or a person with a specific skin tone and profession are all built this way, not stored as one dedicated code point each.

A special code point that changes the appearance of the emoji right before it, most commonly the five skin-tone modifiers. It never stands alone — a skin-tone modifier with no emoji in front of it just displays as a stray color swatch.

An invisible character used to fuse two or more emoji into a single combined image, like joining a woman, a laptop, and additional connectors into one “woman technologist” emoji. If a font or app doesn’t support a ZWJ sequence, it falls back to showing each piece separately.

A reserved block of code points Unicode deliberately leaves undefined, for individual apps, fonts, or companies to assign their own meaning to. Characters here have no universal meaning outside the specific app or font that defined them.

The specific Unicode block containing bold, italic, script, double-struck, and other styled versions of the Latin alphabet and digits. This is the exact block every “fancy text” style-conversion tool, including the ones on this site, actually pulls from.

What happens when a font doesn’t include a glyph for a character your device is trying to display — the operating system substitutes a different font, or shows a blank box (“tofu”), instead of failing outright.

The process of converting equivalent-but-differently-encoded Unicode text into one consistent form, since Unicode sometimes allows the same visible character to be built more than one way internally (for example, an accented letter as one code point versus a plain letter plus a separate combining accent).