Base36 / Base58 / Base62 Encoder — Encode & Decode Large Numbers
Encode any number (decimal or 0x hex, up to 256-bit and beyond) into Base36, Base58 (Bitcoin) and Base62, and decode any of those strings back. Exact BigInt arithmetic, all four representations live side by side, with copy buttons. Runs entirely in your browser.
How to Use
- Pick what you are typing: a decimal number, a hex number (0x…), or a Base36 / Base58 / Base62 string.
- Type or paste your value — the decimal, Base36, Base58 and Base62 forms all update instantly.
- Click any value (or its Copy button) to copy it.
- Numbers use exact BigInt arithmetic, so 256-bit values (Bitcoin keys, UUIDs, hashes) round-trip perfectly.
One number, four ways to write it
This tool takes a single integer — typed as a plain decimal number or as hexadecimal (prefix it with 0x) — and shows it at once as Base36, Base58 and Base62. You can also paste a Base36, Base58 or Base62 string, pick its base, and read the decimal value (and the other encodings) straight back. Everything uses exact BigInt arithmetic, so even a full 256-bit value — a SHA-256 hash, a UUID, a Bitcoin key — converts with no rounding. It all runs in your browser; nothing is uploaded.
Where each base is used
Base58 uses the Bitcoin alphabet 123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz — it deliberately drops the four characters that are easy to confuse when copied by hand (0, capital O, capital I and lowercase l). That is why it encodes Bitcoin addresses and keys, IPFS content IDs and similar identifiers. Base62 (0–9 A–Z a–z) keeps every alphanumeric character, making it the densest case-sensitive encoding — the usual choice for short URLs and compact public IDs. Base36 (0–9 a–z) is case-insensitive, so it survives being uppercased or spoken aloud; it is handy for compact reference, order or coupon codes.
How encoding and decoding work
To encode a number into a base, divide it by the base repeatedly; each remainder selects one character from the alphabet, and the characters read from the last remainder to the first form the string. To decode, fold the string back with Horner’s method: start at 0 and for every character set n = n × base + index, where index is the character’s position in the alphabet. The first character of each alphabet stands for the value 0, which is why 0 encodes as 0 in Base36/62 but as 1 in Base58.
Quick reference
About the Base36 / Base58 / Base62 Encoder — Encode & Decode Large Numbers
Meet the Base36 / Base58 / Base62 Encoder — Encode & Decode Large Numbers: a free, no-fuss tool for everyday tasks with nothing to install and no sign-up. Encode any number (decimal or 0x hex, up to 256-bit and beyond) into Base36, Base58 (Bitcoin) and Base62, and decode any of those strings back. Exact BigInt arithmetic, all four representations live side by side, with copy buttons. Runs entirely in your browser.
How it works
Enter a number and choose your units — the converted value shows instantly. Everything runs locally, so nothing you type leaves your device. Double-check the direction of the conversion and you are set.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
What is the difference between Base36, Base58 and Base62?
All three pack a number into a short alphanumeric string, but use different alphabets. Base36 uses 0–9 and a–z (case-insensitive, 36 symbols). Base62 adds the uppercase letters (0–9, A–Z, a–z = 62 symbols) for shorter strings. Base58 is Base62 minus the four visually ambiguous characters 0, O, I and l — the alphabet Bitcoin uses so hand-copied addresses are less error-prone.
Where is each base used?
Base58 (specifically the Bitcoin alphabet) encodes Bitcoin addresses and keys, IPFS content IDs and other crypto identifiers. Base62 is popular for short URLs and compact database IDs (it is the densest case-sensitive alphanumeric encoding). Base36 gives compact, case-insensitive IDs — handy where the value might be spoken, typed in uppercase, or used in a case-folding system.
How big a number can it handle?
Any size. The encoder uses JavaScript BigInt, so a full 256-bit value (a 64-hex-digit hash or key) converts exactly with no rounding. There is no practical upper limit beyond your browser memory.
How does the encoding work?
To encode, the number is repeatedly divided by the base; each remainder picks one alphabet character, read from last to first. To decode, the digits are folded back with Horner’s method: start at 0, and for each character do n = n × base + index-of-character. Both directions are exact with BigInt.
Why does zero look different in Base58?
Each alphabet’s first character represents the digit value 0. In Base36 and Base62 that first character is literally “0”, so zero encodes as “0”. In the Base58 alphabet the first character is “1”, so zero encodes as “1” — which is why Bitcoin addresses for leading zero bytes begin with 1.
Is anything uploaded?
No. Every conversion runs locally in your browser with JavaScript — your numbers never leave your device.
How do I use the Base36 / Base58 / Base62 Encoder — Encode & Decode Large Numbers?
Simply type or paste your value and read the result, which refreshes the instant you change something. There is nothing to submit and nothing to wait for.
Do I need to install or sign up for anything?
Not at all — it runs in the browser with nothing to install and no account. After it loads once, it even works without an internet connection.
Is my information private?
Yes. Everything happens in your browser. Nothing you type is sent to a server or saved anywhere.
Common Use Cases
Short URLs & IDs
Turn a sequential database ID into a compact Base62 slug (and back) for short links and opaque public identifiers.
Bitcoin & crypto
Read or build the Base58 (Bitcoin alphabet) form of a key or address value, with exact 256-bit precision.
Compact, case-insensitive codes
Base36 packs a number into the shortest string that survives uppercasing — good for coupon, order or reference codes.
Inspecting large values
Paste a 0x hash or huge decimal and instantly see every alphanumeric representation side by side.
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