How Base64 Works: The Algorithm Behind Encoding
A deep dive into the Base64 algorithm: 6-bit groups, the 64-character alphabet, padding rules, and why it was invented in the first place.
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Tags: encoding, developer-tools, base64
How Base64 Works: The Algorithm Behind Encoding Base64 is often described as "encoding binary data as text," but the actual mechanism — how bytes become characters — is worth understanding precisely. This post walks through the algorithm step by step, from the 3-byte input group to the 4-character output, including the padding rules and a complete worked example. The Core Idea Every byte is 8 bits. Base64 works by reinterpreting a stream of 8-bit bytes as a stream of 6-bit values, then mapping each 6-bit value to one of 64 printable ASCII characters. Why 6 bits? Because 2^6 = 64, so 6 bits can represent exactly 64 distinct values — one for each character in the Base64 alphabet. The key constraint: 8 and 6 don't divide evenly. The LCM of 8 and 6 is 24 — which means you need exactly 3 bytes…
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