Base64

Two encodings, two different jobs Both Base64 and URL encoding replace “unsafe” characters with safe ones. That surface similarity is why they get mixed up — and why people sometimes apply both when one would do, or apply the wrong one entirely. The short version: Base64 makes binary data survive a text-only channel. Percent-encoding makes text survive a URL. What each one actually does Base64 rewrites bytes using a 64-character alphabet (A–Z a–z 0–9 + /, plus = padding). Every 3 bytes become 4 characters, so output grows by about 33%. ...

The problem Base64 solves Many systems only transport text. Email was designed for 7-bit ASCII, JSON is defined as text, and HTML attributes hold strings. But the things we actually want to move around — images, PDFs, encryption keys, binary protocol buffers — are bytes that can easily include control characters, quotes, or newlines. If you paste raw binary into a text channel, something will eventually eat a byte: a line ending gets rewritten, a quote terminates a string early, a proxy strips a NUL. Base64 gives you a safe envelope by re-encoding those bytes using only 64 characters that every text system agrees on: ...