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Build a Base64 Encoder/Decoder

Implement RFC 4648 base64 encoding from scratch: the alphabet, 3-byte to 4-char encoding, padding, decoding with error handling, and the URL-safe variant used in JWT. Used in email, data URIs, HTTP Basic auth, and PEM-encoded keys.

beginner8 lessons4 chapters8 graded exercisesPython
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What you’ll have built

Chapter by chapter. Every step is a graded exercise.

  • The Basics
  • Encoding
  • Decoding
  • Variants
Starts in Python — solve in the language you choose in the editor, same tests either way.

Curriculum

4 chapters, 8 lessons. Each lesson is a short read, one graded exercise, and a quiz.

  1. 1Why Base64?Read · exercise · quiz
  2. 2The Base64 AlphabetRead · exercise · quiz
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Build a Base64 Encoder/Decoder