What Is Base64 Encoding (and How to Decode It)
Base64 encodes binary data as 64 safe text characters so it survives text-only channels. Learn how it works, when to use it, and why it is not encryption.
Base64 encoding represents binary data using 64 safe ASCII characters — A–Z, a–z, 0–9, plus + and / — so the data can travel through text-only systems like email or JSON without being corrupted. Decoding simply reverses the process to recover the original bytes.
How it works
Base64 takes three bytes (24 bits) at a time and splits them into four 6-bit groups, each mapped to one character. When the input length is not a multiple of three, one or two = characters pad the end.
The size trade-off
Because every 3 bytes become 4 characters, Base64 output is about 33% larger than the original. That is the cost of making binary safe to embed as text.
Common uses
- Data URIs — embedding images directly in CSS or HTML
- Email attachments — MIME encodes files as Base64
- JWT — the header and payload are Base64url-encoded
- HTTP Basic auth — credentials are Base64-encoded (not encrypted)
It is not encryption
This is the key point: Base64 is encoding, not security. Anyone can decode it instantly, so never use it to hide passwords or secrets. It only makes data transport-safe, not private.
Encode or decode now
Paste text into the Base64 encoder/decoder to convert both ways in your browser — nothing is uploaded. Working with images? Try image to Base64. Related: What is a JWT and how to decode it.