Base64 Encoder & Decoder

What Base64 is

Base64 is a way to represent binary data using 64 printable ASCII characters: A–Z, a–z, 0–9, plus + and /. Every three bytes of input become four Base64 characters. Padding with = fills out the final group when the input length is not a multiple of three.

It is an encoding, not encryption. Anyone can decode Base64. It adds no secrecy and usually makes the data about a third larger.

Text, bytes and UTF-8

Computers store text as bytes. UTF-8 is the most common way to turn characters into bytes, and it can represent almost every writing system. This tool converts your text to UTF-8 bytes before encoding, and decodes bytes back to UTF-8 text. If the decoded bytes are not valid UTF-8, it reports an error instead of showing garbled output.

URL-safe Base64

Standard Base64 uses + and /, which have special meanings in URLs. The URL-safe variant uses - and _ instead and often removes the = padding. The checkbox enables that output. Decoding accepts either alphabet, so you can paste a value without changing the setting.

Common uses

• Embedding small images or fonts in CSS or HTML as data URLs.
• Email attachments, where MIME encodes binary files as text.
• Carrying binary values inside JSON, XML or other text formats.
• HTTP Basic authentication headers.
• Parts of JSON Web Tokens (JWT), which use URL-safe Base64.

Common mistakes

• Assuming it is secure. It is not. Use encryption and HTTPS for confidentiality.
• Double encoding. If a value already looks like Base64, check before encoding it again.
• Ignoring line breaks. Some Base64 output is wrapped across lines. Remove the whitespace before decoding if a tool rejects it.
• Encoding huge files. Base64 is fine for small payloads. For large images and downloads, send the binary directly.

For a longer explanation of the format, read what is Base64.