Mathematical symbol Up Tack
About this character
The character ⊥ carries the official Unicode name “Mathematical symbol Up Tack” and the code point U+22A5, which is 8869 in decimal. It belongs to the Mathematical Operators block (U+2200–U+22FF), which gathers the operators, quantifiers and relations of algebra, logic and set theory.
In memory, ⊥ takes 3 bytes in UTF-8 (0xE2 0x8A 0xA5) and 1 in UTF-16 (0x22A5). That difference is why badly configured forms or databases garble this character: they assume one byte per character.
How to type ⊥
| System | What to do |
|---|---|
| Windows | In Word or WordPad, type 22A5 and press Alt + X to turn the code into the character. |
| macOS | On a Mac, open the Character Viewer with Ctrl + ⌘ + Space and search for “Mathematical symbol Up Tack”. |
| Linux | On Linux (GTK), type Ctrl + ⇧ + U, 22A5 then press Enter. |
| HTML / Web | In an HTML page, write ⊥. Use \22A5 in CSS, \u22A5 in JavaScript and \u22A5 in Python. |
| On this site | The simplest route is the Copy button above: the character goes straight to your clipboard, ready to paste anywhere. |
Keyboards that include ⊥
This character is not on any common physical layout, so the Copy button above is the quickest way to get it into a document.
Codes and encodings
| Property | Value |
|---|---|
| Code point | U+22A5 |
| Unicode block | Mathematical Operators (U+2200–U+22FF) |
| Decimal | 8869 |
| Hexadecimal | 0x22A5 |
| Octal | 021245 |
| Binary | 10001010100101 |
| UTF-8 bytes | 0xE2 0x8A 0xA5 |
| UTF-16 units | 0x22A5 |
| Named HTML entity | ⊥ |
| Decimal HTML entity | ⊥ |
| Hex HTML entity | ⊥ |
| CSS escape | \22A5 |
| JavaScript escape | \u22A5 |
| Python escape | \u22A5 |
| URL encoding | %E2%8A%A5 |
Frequently asked questions
What is the Unicode code for ⊥?
Its code point is U+22A5, which is 8869 in decimal and 021245 in octal. In HTML you can write it as ⊥ or ⊥.
Why does ⊥ show up as a box or a question mark?
An empty box means the font has no glyph for U+22A5. The character is still in the text: switching to a font that covers the block (Noto, DejaVu or Segoe UI Symbol) makes it appear.
Can I use ⊥ in a filename, a URL or a password?
In a URL it must be encoded as %E2%8A%A5. Modern filesystems accept it, though it is still risky when moving files between systems. For passwords, some forms reject non-ASCII characters outright.