Bitcoin symbol
By far the most commonly used symbol for Bitcoin is ₿, a capital letter B with two falling strokes at the top and bottom. This symbol was designed by Satoshi Nakamoto for the icon of an early version of the original Bitcoin client, though the very first versions of the Bitcoin client used "BC" instead of any special symbol. Presumably the symbol was intended to look similar to other currency symbols. The symbol represents the currency unit "bitcoin" (100 million satoshi), as well as the Bitcoin network and currency itself. The bitcoin currency unit is also commonly given the informal currency code BTC.
The Bitcoin sign is part of Unicode 10.0 (released June 2017)[1] with code point U+20BF (₿). As of June 2017, font support for the Bitcoin sign is in macOS Sierra, iOS, Android O beta, Windows 10 Creators Update and several Linux releases. After being rejected in 2011,[2] the Bitcoin sign was accepted for Unicode in November 2015[3] and first appeared in Unicode 10.0 in 2017.[1]
Historically, similar looking Unicode symbols such as the Thai Baht (฿) have been used because the Unicode standard at the time had not included a symbol for Bitcoin. The capital letter B with stroke (Ƀ) was also used in contexts where it was likely that using the Baht symbol would cause confusion.
Currency code
The ISO 4217 currency code for Bitcoin is XBT. However, at the moment it is an unofficial code according to the ISO 4217 standard. The unit name BTC is also commonly used to represent one bitcoin, but it violates ISO 4217 because it begins with "BT", the country code of Bhutan. Bhutan does not actually use the code BTC for any currency, and XBT has not yet defined which unit it represents (just that it represents some unit of bitcoin), so the Bitcoin community is likely to continue using mainly BTC as a unit name and currency code for some time.
A formal application by the Financial Standards Working Group of the Bitcoin Foundation is nearing completion.[still true?] This application would request ISO 4217 standard to support XBT.
Inserting the symbol
In lieu of the Bitcoin symbol being included in the Unicode standard and its adoption into typographic fonts, ₿ can be included in many documents by other means. This section focuses on online publications but the basic concepts apply to all publishing forms.
Image
The Bitcoin symbol can be inserted as an image, as is done in the opening sentence of this page. The benefit of this method is that any client that can display images in line with text will be able to display the symbol. The down side to this method is that as an image, it does not always degrade as nicely as a font. If using raster image, scaling the image up/down (to fit with surrounding text) may result in pixelation, inappropriate filtering, and other issues typical of raster images. If using a vector image, scaling concerns do not apply but the display would still not benefit from font-specific rendering features such as hinting. Both forms also suffer from client-specific considerations such as whether or not a box will be drawn around the image and the general inability to easily style its display; applying color requires specific CSS, and italicizing would require a CSS skew transform, for example.
When using an image in running text on a webpage it's generally a good idea to set the alt property to an appropriate value. For example, when depicting amounts you might use alt="BTC". Text including the symbol copied and pasted will then remain syntactically correct, replacing the symbol with BTC.
Sample HTML code:
.btc { height:1em; position:relative; top:0.17em; cursor:text; }
...
Please send <img src="/btc-sans.png" alt="BTC" class="btc" />0.01 to ...
Please send <img src="/btc-sans.svg" alt="BTC" class="btc" />0.01 to ...
Font Awesome icon
The Font Awesome collection of icons and symbols also includes the Bitcoin symbol.[4]
Sample HTML code:
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css">
...
Please send <i class="fa fa-btc"></i>0.01 to ...
Font
As few fonts include the Bitcoin symbol, a special font was created by Theymos, originally for the BitcoinTalk forum.[5] The font consists of only the Bitcoin symbol (₿) used in the glyph for the capital letter B. The text "BTC" can be entered and styled with this font, causing it to be replaced entirely with just the symbol on those systems that support this font, while on other systems the text "BTC" is retained. Similarly, copying and pasting text will still retain "BTC". This method is used on BitcoinTalk and the Bitcoin Wiki.
Sample HTML code:
@font-face { font-family: BTC; src: url(BTC.ttf); }
...
Please send <span style="font-family:BTC, sans-serif">BTC</span>0.01 to ...