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Base64 Encoder & Decoder

Encode text or files to Base64, or decode Base64 back to plain text. Standard and URL-safe modes. Runs locally.

Frequently Asked Questions

What is Base64 encoding?
Base64 converts binary data into a text string using 64 ASCII characters (A-Z, a-z, 0-9, +, /). It is used to embed binary content in text-only channels like JSON, email (MIME), data URIs, and HTTP headers.
Why does the encoded output grow by ~33%?
Every 3 bytes of input become 4 Base64 characters (6 bits each). That 4/3 ratio plus padding means the encoded string is roughly 33-37% larger than the original binary.
Is my data uploaded?
No. Encoding and decoding happen entirely in your browser using the built-in btoa/atob functions and TextEncoder. Nothing is transmitted.
Does Base64 encrypt my data?
No. Base64 is encoding, not encryption. Anyone can decode the string back to the original data instantly. Do not use it to hide passwords, secrets, or sensitive information.
What is the difference between standard and URL-safe Base64?
Standard Base64 uses + and / which conflict with URL syntax. URL-safe Base64 replaces them with - and _ and omits trailing = padding. Use URL-safe when the string will appear in a URL, filename, or cookie.

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