Base64 Encoder / Decoder

What is Base64 encoding?

Base64 converts binary data or text into a string of ASCII characters using 64 characters: A–Z, a–z, 0–9, + and / with = as padding. It is used to embed images in HTML/CSS, transmit data in email (MIME), store binary data in JSON, and pass data safely through URLs and APIs.

What is URL-safe Base64?

Standard Base64 uses + and / which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _ so the encoded string can be used in URLs without percent-encoding. It is commonly used in JWTs (JSON Web Tokens) and OAuth tokens.

Does Base64 encrypt my data?

No. Base64 is encoding, not encryption. Anyone who sees a Base64 string can decode it instantly — it provides zero security. Do not use Base64 to protect sensitive data like passwords or private keys. For security, use proper encryption (AES-256, RSA).

Why does Base64 output end with == or =?

Base64 encodes every 3 bytes into 4 output characters. If the input length is not divisible by 3, = padding is added to make the output a multiple of 4. One = means 1 padding byte was added; == means 2 bytes were added.

How much larger is Base64 vs the original?

Base64 output is approximately 33% larger than the original input (every 3 bytes become 4 characters). A 100-byte string becomes ~136 characters in Base64. This overhead is why Base64 is used for compatibility, not compression.

Is my data safe when using this tool?

Yes. All encoding and decoding runs in your browser using JavaScript's built-in btoa() and atob() functions. No data is sent to any server. You can safely encode sensitive strings — everything stays on your device.