Base58 Decode

What the Base58 decoder does

This takes a Base58 string and turns it back into the original text it was made from. Paste the Base58 in, press Convert, and copy or download the result. It is the reverse of the Base58 Encode tool, which is where the fuller story of Base58, the Bitcoin origin and the missing characters, is laid out.

The decoding runs in your browser, so nothing you paste is uploaded.

How to use it

1. Paste your Base58. Type or paste it, or upload a plain text file.
2. Press Convert. The decoded result appears.
3. Copy or Download the result.

Case matters, so paste it exactly

Unlike Base32, Base58 is case-sensitive, so a capital letter and its lowercase version are completely different values. That means you have to paste the string exactly as it was given to you, with the capitals and lowercase letters intact. Change one and you decode to different data, or hit an error. The flip side of Base58's careful alphabet is that you will never see a 0, a capital O, a capital I, or a lowercase l in a valid string, so if one of those has crept in, something was copied wrong.

What you get from a Bitcoin address or key

Two things to expect if you paste in something like a Bitcoin address, and both come down to the same root. First, the decoded output will look like a jumble of strange characters rather than readable words. That is right and expected: an address is raw data, a hashed key with some extra bytes, and it was never text, so turning it back gives you those raw bytes, which display as gibberish.

Second, and more important, this tool does plain Base58, so it does not check the address for you. A Bitcoin address carries a built-in checksum, under the Base58Check scheme described on the encode page, and proper wallet software uses that checksum to catch a mistyped address before any coins move. A plain Base58 decode just converts the characters back to bytes without verifying that checksum, so it cannot tell you whether an address is valid or has a typo. If that is what you actually need, you want a Bitcoin address validator that understands Base58Check, not a plain decoder.

How it works

The decoder treats your Base58 string as one large number written in base 58, works out that number from the position of each character in the alphabet, and converts it back into bytes. Leading 1 characters, which stand for zero in Base58, are turned back into leading zero bytes. The same base-x library that powers the encoder, set up with the Bitcoin alphabet, handles the decode.

Questions people ask

How do I decode a Base58 string?

Paste it exactly, keeping the original upper and lower case, and press Convert. If it was made from text, the original text appears.

Why is my decoded address unreadable?

Because an address or key is raw data, not text. Decoding returns the original bytes faithfully, but those bytes were never readable characters, so they show as a jumble.

Can it tell me if a Bitcoin address is valid?

No. This is a plain Base58 decoder and does not verify the Base58Check checksum that addresses carry. Checking an address for typos needs a validator built for Base58Check.

Does case matter when I paste?

Yes. Base58 is case-sensitive, so the string must be pasted with its capitals and lowercase letters exactly as given, or it will not decode correctly.

References

1. base-x, a base encoder and decoder for any alphabet, including Base58 (npm package). https://www.npmjs.com/package/base-x
2. Bitcoin Wiki, Base58Check encoding. https://en.bitcoin.it/wiki/Base58Check_encoding