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Encode and decode Base64 strings. Convert text for data URIs, APIs, and safe data transmission.
Base64 is a binary-to-text encoding scheme that converts binary data into a set of 64 printable ASCII characters. It is commonly used to embed images in HTML or transmit data over text-based protocols.
0 characters
A-Z(26 characters)a-z(26 characters)0-9(10 characters)+ /(2 characters)=(end of string)Encoding: Converts each character to its UTF-8 byte representation, then groups bytes into 6-bit chunks mapped to Base64 characters.
Decoding: Reverses the process by converting Base64 characters back to 6-bit values, reassembling bytes into the original text.
100% Client-Side: All processing happens in your browser. Your data never leaves your device.
| Characters | Range |
|---|---|
| A–Z | Characters 0–25 |
| a–z | Characters 26–51 |
| 0–9 | Characters 52–61 |
| + | Character 62 |
| / | Character 63 |
| = | Padding character |
Formula
output_size = ⌈input_bytes / 3⌉ × 4 charactersinput_bytes = Number of bytes in the original binary data
⌈ ⌉ = Ceiling function — rounds up to nearest whole number
× 4 = Every 3 bytes map to 4 Base64 characters (33% overhead)
Worked Example
Encoding "Hi!" (3 bytes)
Did you know? Base64 was standardized in 1987 by RFC 989 for use in Privacy-Enhanced Mail (PEM). Today it is used everywhere from embedding images in CSS data URIs to encoding JWT payloads and HTTP Basic Auth credentials.
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