Binary to Base64 Converter: Bits to Base64

How to convert binary to Base64

1. Paste the bits into Input · Binary.
2. The Base64 appears in Output · Base64 as you type.
3. Under the output, Padding (=) adds or removes trailing = signs, and Line wrap breaks the result every 64 or 76 characters for PEM or MIME use.
4. Copy output or Download. To check the result, flip the direction with Base64 → Binary or open Base64 to Binary.

How the input is read

The converter decides between two readings:

• Grouped. If the bits are split by spaces, new lines, commas, semicolons or |, and no group is longer than 8 bits, each group is one byte. Short groups are allowed, so 7-bit ASCII such as 1001000 1101001 reads as Hi, and 1 0 1 is three bytes with the values 1, 0 and 1.
• Continuous. If there are no separators, or any group is longer than 8 bits, all the bits are joined and cut into bytes from the left. The total must then be a multiple of 8.

0b prefixes are skipped in both cases. A character other than 0, 1 or a separator stops the conversion with its position.

Examples

Every 24 bits become exactly four characters, because Base64 reads the bit stream 6 bits at a time. All zeros map to A, the first character of the alphabet, and all ones to /, the last. The output is about a sixth as long as the binary input: 8 bits on the way in, 1.33 characters on the way out, per byte.

Where binary strings come from

Bit strings turn up in protocol specs and datasheets, in bitmask constants, in exercises on number systems, and in test vectors written out bit by bit. Base64 is the compact way to put the same bytes into JSON, a config file or an HTTP header. If you have the bits as hex already, Hex to Base64 is shorter to paste; if you have decimal byte values, use Decimal to Base64.

Binary to Base64 in code

import base64

bits = "0100100001101001"
data = int(bits, 2).to_bytes(len(bits) // 8, "big")
base64.b64encode(data).decode()       # 'SGk='

int(bits, 2) drops leading zeros, but to_bytes with the original length puts them back. For space-separated bytes, bytes(int(b, 2) for b in s.split()) is simpler.

const bits = "01001000 01101001";
Buffer.from(bits.split(" ").map(b => parseInt(b, 2))).toString("base64");   // 'SGk='

The Python and Node.js pages show the reverse direction and file handling.

Common problems

• “15 bits is not a whole number of bytes”. The count in the message tells you how far off you are. Usually a leading zero was dropped from the first byte, as in 1001000 written for 01001000 inside an unbroken string.
• Unexpected Base64 from grouped input. Check that no group has 9 or more digits. One long group switches the whole input to continuous mode and the byte boundaries move.
• Letters or O instead of 0. Text copied from PDFs and chat apps sometimes contains a capital O or other look-alikes. The error message points at the position.

FAQ