A JavaScript Base62 encode/decoder

Base62 encoding converts numbers to ASCII strings (0-9, a-z and A-Z) and vice versa, which typically results in comparatively short strings. Such identifiers also tend to more readily identifiable by humans.

• 999 ≙ "g7"
• 9999 ≙ "2Bh"
• 238327 ≙ "ZZZ"

npm install base62

alternatively using Yarn:

yarn add base62

For backwards compatibility, Base62.js exposes v1.x's API by default – see Legacy API below. For efficiency, v2.x's modernized API allows selectively importing individual modules instead:

var base62 = require("base62/lib/ascii");

base62.encode(999);  // "g7"
base62.decode("g7"); // 999

This uses the default ASCII character set for encoding/decoding.

It's also possible to define a custom character set instead:

var base62 = require("base62/lib/custom");

var charset = "~9876543210ABCDEFGHIJKLMNOPQRSTU$#@%!abcdefghijklmnopqrstuvw-=";
charset = base62.indexCharset(charset);

base62.encode(999, charset);  // "F3"
base62.decode("F3", charset); // 999

Note that indexCharset typically expects the respective string to contain exactly 62 unique character, but does not validate this for efficieny. In fact, it's also possible to use characters sets with more than 62 characters in order to achieve shorter identifiers for large numbers.

Base62.js v1.x's API is maintained for backwards compatibility.

var base62 = require("base62");

base62.encode(999);  // "g7"
base62.decode("g7"); // 999

This uses the default ASCII character set for encoding/decoding.

It's also possible to define a custom character set instead:

var base62 = require("base62");

var charset = "~9876543210ABCDEFGHIJKLMNOPQRSTU$#@%!abcdefghijklmnopqrstuvw-=";
base62.setCharacterSet(charset);

base62.encode(999);  // "F3"
base62.decode("F3"); // 999

setCharacterSet ensures that the respective string contains exactly 62 unique characters.

Source code is hosted on GitHub. Please report issues or feature requests in GitHub Issues.

• Fork the project.
• Make your feature addition or bug fix.
• Add tests for it. This is important so I don't break it in a future version unintentionally.
• Send me a pull request. Bonus points for topic branches.

• Update the version number in package.json.
• Commit this change with the respective version number as commit message (e.g. "1.2.3").
• Create an annotated tag, using the prefixed version number (e.g. git tag -am "1.2.3" v1.2.3).
• Publish the new version: git push --tags origin master and npm publish.

Copyright (c) 2024 Andrew Nesbitt. See LICENSE for details.