Base64 is a binary-to-text encoding scheme that converts binary data into a string of 64 printable ASCII characters. It was created to safely transmit binary data through text-only systems like email and URLs.
Understanding Base64 is fundamental for web developers, email engineers, and anyone working with APIs. It appears in JWT tokens, data URIs, email attachments, and API authentication.
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How to What is Base64 Encoding? — Complete Explanation
- Binary data is split into groups of 3 bytes (24 bits)
- Each 24-bit group is divided into 4 groups of 6 bits
- Each 6-bit value (0-63) maps to a character in the Base64 alphabet
- The alphabet is: A-Z (0-25), a-z (26-51), 0-9 (52-61), + (62), / (63)
- If input is not divisible by 3, = padding is added
- Try encoding "Hello" → "SGVsbG8=" with our tool above
Pro Tips
- "Hello" in Base64 = "SGVsbG8=" — every 3 input chars become 4 output chars
- The = at the end is padding — it means the last group had fewer than 3 bytes
- Base64 is NOT encryption — anyone can decode it. It is just a format conversion.
- The name "Base64" comes from using 64 different characters (2^6 = 64)
Frequently Asked Questions
Is Base64 encoding the same as encryption?
No. Base64 is encoding (format conversion), not encryption (security). Anyone can decode Base64 instantly. Never use Base64 to "hide" sensitive data.
Why was Base64 invented?
Email systems (SMTP) from the 1970s could only handle 7-bit ASCII text. Base64 was created to safely transmit binary files (images, documents) through these text-only channels.
Where is Base64 used today?
Everywhere: email attachments (MIME), JWT tokens, data URIs in HTML/CSS, API authentication headers, JSON API payloads, and storing binary data in XML/databases.
How much does Base64 increase size?
Base64 increases data size by exactly 33% (plus a few bytes for padding). 3 bytes of input always become 4 bytes of output.
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