The Siddham block spans U+11580–U+115FF, 128 codepoints in Plane 1 (Supplementary Multilingual Plane). 92 are assigned in Unicode 16.0; the other 36 are reserved for future characters.
All of its characters belong to the Siddham script.
By general category: 51 other letters (Lo), 23 other punctuation (Po), 10 non-spacing marks (Mn), 8 spacing marks (Mc).
The first 72 arrived in Unicode 7.0 (2014); later additions came in 8.0 (20).
Because it lies outside the BMP, every character here takes four bytes in UTF-8 and a surrogate pair in UTF-16.