Curly Quotes vs Straight Quotes

Typographic or “smart” quotes (“” and ‘’) are the curled quotation marks used in professionally typeset text, while straight quotes (" and ') are the ASCII characters inherited from typewriter conventions. The left double quote (U+201C) and right double quote (U+201D) are distinct code points, as are the left single quote (U+2018) and right single quote (U+2019). Word processors like Microsoft Word and Google Docs automatically substitute straight quotes with curly quotes, but plain-text editors, code editors, and HTML attributes require straight quotes. Using curly quotes inside HTML attribute values or programming strings will cause syntax errors, so developers must always use straight ASCII quotes in code. Notably, the right single quote (U+2019) also doubles as a typographic apostrophe, which is why “don’t” in a word processor looks slightly different from “don't” typed in a terminal.