Why encode Base64 locally?
Base64 is a common format used to encode binary data or complex strings (like JSON Web Tokens, API Keys, or email attachments) into safe, printable ASCII text.
Because developers frequently deal with API secrets or sensitive user data that happens to be Base64-encoded, pasting those strings into a remote, cloud-hosted decoder is a massive security risk. This utility uses native browser functions (btoa() and atob()) to guarantee your data never leaves your current tab.
RFC 4648 Conversion Logic
Base64 groups binary data into 24-bit chunks (three 8-bit bytes) and splits them into four 6-bit units. Each 6-bit unit maps to one of 64 characters in the index table (A-Z, a-z, 0-9, +, /):
- Input: 3 bytes = 24 bits
- Output: 4 ASCII characters (33% size expansion)
- Padding (
=): Appended when byte length is not divisible by 3
Standard Base64 vs Base64URL
In URL query strings and JWT headers, the standard + and / characters cause encoding conflicts. The Base64URL standard replaces them:
- + is replaced with - (minus)
- / is replaced with _ (underscore)
- Padding
=is typically stripped
Frequently Asked Questions
Is my text data or decoded secret sent to any remote server?
No. Base64 encoding and decoding are executed 100% locally in your browser using client-side JavaScript. Zero bytes are uploaded to the cloud.
Does this tool support UTF-8 characters and emojis?
Yes. The encoding and decoding engines handle full UTF-8 byte sequences, allowing safe conversion of multilingual text, Arabic, Chinese, and emojis.
Is Base64 considered encryption?
No. Base64 is an encoding format designed for safe data transport over ASCII-only protocols, not cryptographic encryption.