SuperCalc

Base64 Encoder & Decoder

Encode text to Base64 or decode Base64 back to readable text. Character count and byte size shown for both input and output.

Base64 Encoder / Decoder

Encode text to Base64 or decode Base64 back to text.

How it works

Base64 encoding converts arbitrary binary data into a string of printable ASCII characters. Every 3 bytes of input produce 4 characters of output, using the alphabet A-Z a-z 0-9 + / plus = for padding.

This tool handles full UTF-8 text correctly. Multi-byte characters (accented letters, CJK, emoji) are first encoded to UTF-8 bytes, then those bytes are Base64-encoded. Decoding reverses the process faithfully.

All processing runs in your browser using the native btoa() and atob() functions with a UTF-8 wrapper. No data leaves your device.

FAQ

What is Base64?
Base64 is a binary-to-text encoding scheme that represents binary data as a string of printable ASCII characters. It uses 64 characters (A-Z, a-z, 0-9, +, /) plus = for padding. It is not encryption — it is a reversible encoding.
When should I use Base64?
Base64 is commonly used to embed binary data in text-based formats: images in HTML/CSS (data URIs), file attachments in email (MIME), credentials in HTTP Basic Auth headers, and binary data in JSON payloads.
What is the difference between Base64 and encryption?
Base64 is encoding, not encryption. Anyone can decode a Base64 string without a key. It provides no security whatsoever. Use it for transport compatibility, not for protecting sensitive data.
Why does Base64 make strings longer?
Base64 encodes 3 bytes of input into 4 characters of output, resulting in roughly 33% size increase. This overhead is the cost of representing arbitrary binary data using only printable ASCII characters.
What is URL-safe Base64?
Standard Base64 uses + and / characters, which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _, and often omits the trailing = padding. This variant is used in JWTs and data URIs in URLs.
Is Base64 encoding secure?
No. Base64 is trivially reversible. Never use Base64 to protect passwords, API keys, or sensitive data. It is a transport encoding, not a security mechanism. Use proper encryption (AES, RSA) for security.

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