Render LaTeX as you type, with mixed prose, MathML copy and a snippet palette
In single-formula mode write \frac{a}{b} straight in. In mixed mode $…$ is an inline formula, $$…$$ is a display formula and \$ is a literal dollar sign. Click a snippet to insert it at the caret.
Enter a formula to see it rendered here
KaTeX renders locally and is as strict as TeX: a misspelled command reports its position in the line. KaTeX covers math typesetting only — diagrams and TikZ need a full LaTeX installation. MathML pastes into Word, Notion or a paper with the formula still editable.