How is the Flickr alphabet different from Bitcoin's Base58?

Both alphabets contain the same 58 characters and both omit the look-alikes zero, capital O, capital I and lowercase L. The difference is ordering: Flickr lists the digits, then lowercase letters, then uppercase letters, whereas Bitcoin lists digits, then uppercase, then lowercase. The same number therefore produces different strings in each scheme.

What does Flickr use Base58 for?

Flickr assigns each photo a large numeric ID and encodes that integer in Base58 to make the short flic.kr URLs. Base58 keeps the slug compact while avoiding characters that are easy to misread or that need escaping inside a URL.

Should I use integer mode or text mode?

Use integer mode when you have a numeric ID such as a photo ID, because Flickr encodes the number itself. Use text or bytes mode when you want to round-trip arbitrary data through the same alphabet, which preserves leading zero bytes as leading ones.

Why does decoding a slug give a huge number?

Base58 represents a single large integer, so decoding a multi-character slug in integer mode reconstructs that big number. For photo IDs this is exactly the original numeric ID Flickr started with before encoding.

Does any data leave my browser?

No. All conversions run locally in JavaScript, so your IDs and data are never uploaded anywhere.

Base58 Flickr Encoder/Decoder

Flickr Base58 is the encoding behind short flic.kr photo links. It uses the same 58 unambiguous characters as Bitcoin’s Base58 but orders them differently, placing lowercase letters before uppercase. This tool encodes integers or UTF-8 text into Flickr Base58 and decodes them back, entirely in your browser.

How it works

Base58 is positional base conversion against a 58-symbol alphabet — here 123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ:

In integer mode, the input number is divided by 58 repeatedly; each remainder selects a symbol, and the symbols are read most-significant first. This is exactly how Flickr turns a photo ID into a slug.
In bytes mode, the input is treated as one big-endian integer and converted the same way, with each leading zero byte encoded as a leading 1 so it round-trips.
Decoding accumulates the characters back into the integer (integer mode) or into bytes (bytes mode).

Because the alphabet omits 0, O, I, and l, any string containing those characters is invalid and is rejected.

Tips and example

To recreate a Flickr short URL, take the numeric photo ID and encode it in integer mode — the resulting slug is what appears after flic.kr/p/. Decoding that same slug in integer mode returns the original ID. If you switch a value between this tool and the Bitcoin Base58 tool you will get different strings for the same number, because only the symbol ordering differs; that is the intended, defining distinction between the two variants.