What ♯ means
It raises a written note by one chromatic semitone. F♯ is still an F note, with its pitch raised. In a key signature, a sharp sets that pitch for the matching note; beside one note, it is an accidental—an alteration marked for that note.
The sharp sign developed gradually from medieval B notation. Singers learned pitches in six-note patterns called hexachords: square B (b quadratum) marked the “hard” form, while rounded B marked the “soft” form. A sharp-like form developed from the square sign. Such signs are documented in the 15th and 16th centuries, and printed forms kept changing in the 17th century.
In the last quarter of the 16th century, the French term dièse was linked to Renaissance efforts to describe the chromatic and enharmonic divisions in ancient Greek music theory—ways of dividing musical intervals.
How do I type ♯ in HTML?
In HTML, enter ♯. This numeric character reference renders as ♯ in HTML; in ordinary text, it remains code.
Notation-specific; in a score, it marks a deliberate pitch change.
For exact notation, # is the wrong character.
Don't confuse it with
1Combination ideas
3Questions people ask
1Why does ♯ show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type ♯
♯\266FCodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.