What is the HTML code for 𝕀?

Use the named entity &Iopf;, or 𝕀 (decimal) or 𝕀 (hex).

What is the UTF-8 encoding of U+1D540?

F0 9D 95 80 (hex), 4 bytes. In a URL it is %F0%9D%95%80.

How do I write U+1D540 in JavaScript or Python?

JavaScript: \u{1D540} or \uD835\uDD40. Python: \U0001D540.

𝕀 Mathematical Double-Struck Capital I: copy and paste

𝕀 Mathematical Double-Struck Capital I

Uppercase letter. Codes for HTML, CSS, JavaScript, Python and other languages.

𝕀

𝕀 is the Unicode character MATHEMATICAL DOUBLE-STRUCK CAPITAL I, code point U+1D540 (decimal 120128) in the Mathematical Alphanumeric Symbols block, added in Unicode 3.1. In HTML write &Iopf;, and in UTF-8 it is the 4 bytes F0 9D 95 80.

Codes

Where	How to write it
Code point	U+1D540
Decimal	120128
UTF-8 bytes	F0 9D 95 80
UTF-16 (big-endian)	D835 DD40
UTF-32	0001D540
HTML decimal	𝕀
HTML hex	𝕀
HTML named	&Iopf;
CSS	\1D540
JavaScript	\u{1D540} or \uD835\uDD40
JSON	\uD835\uDD40
Python	\U0001D540
Python by name	\N{MATHEMATICAL DOUBLE-STRUCK CAPITAL I}
Java, C#	\uD835\uDD40
Rust, Swift	\u{1D540}
Go, C, C++	\U0001D540
URL (percent-encoded)	%F0%9D%95%80

JavaScript and JSON strings store text as UTF-16, so this character takes two code units (a surrogate pair) and "𝕀".length is 2. Python 3 strings count code points, so its length there is 1.

Properties

Property	Value
Name	MATHEMATICAL DOUBLE-STRUCK CAPITAL I
Code point	U+1D540 (decimal 120128)
Block	Mathematical Alphanumeric Symbols (U+1D400–U+1D7FF)
General category	Lu: Uppercase letter
Script	Common
Bidirectional class	L: Left-to-right
Mirrored in right-to-left text	No
First in Unicode version	3.1

Decomposition

MATHEMATICAL DOUBLE-STRUCK CAPITAL I has a compatibility decomposition (font) to the sequence below. NFKC and NFKD normalisation replace it with that sequence, which can change how text looks, so use them for search, not for storage.

I U+0049 Latin Capital Letter I

Nearby in Mathematical Alphanumeric Symbols

All 997 characters: Mathematical Alphanumeric Symbols.

Official reference

Unicode code chart: Mathematical Alphanumeric Symbols (PDF, unicode.org)

Questions people ask

What is the HTML code for 𝕀?: Use the named entity &Iopf;, or 𝕀 (decimal) or 𝕀 (hex).
What is the UTF-8 encoding of U+1D540?: F0 9D 95 80 (hex), 4 bytes. In a URL it is %F0%9D%95%80.
How do I write U+1D540 in JavaScript or Python?: JavaScript: \u{1D540} or \uD835\uDD40. Python: \U0001D540.

Source

Unicode Character Database 18.0.0 (Unicode License v3); HTML entity names from the WHATWG HTML Standard (CC BY 4.0). The encodings above are computed from the code point and checked against Python's encoders. How the character looks depends on your fonts.

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