Base64 encode and decode
Runs in your browserPaste text to encode it to Base64, or paste Base64 to decode it, with full UTF-8 support (accents, emoji, any script) and a URL-safe variant. URL percent-encoding is one click away.
Fill in the fields to see the result.
How to use it
- Pick Encode or Decode (or URL-encode / decode).
- Paste text, or drop a text file onto the box.
- The output updates as you type; copy it or download JSON.
Details
- Encoding
- UTF-8 bytes to standard Base64 (RFC 4648), or URL-safe with - and _ and no padding
- Decoding
- Accepts standard or URL-safe, with or without padding; reports byte count and whether it is valid UTF-8
- URL encoding
- encodeURIComponent / decodeURIComponent
Questions
Is Base64 encryption?
No. Base64 is an encoding that anyone can reverse. Don't use it to hide passwords or secrets.
Why does my decoded text look garbled?
The data is probably binary (an image or a zip), not text. The tool tells you when the bytes are not valid UTF-8.
What is URL-safe Base64?
A variant that uses - and _ instead of + and /, and drops the = padding, so the result can go in a URL or filename. JWTs use it.
Is what I type sent anywhere?
No. The calculation runs in this browser tab with the same code our MCP server uses. Nothing you type is sent to a server or saved, apart from settings like filing status, which stay in this browser.
Can an AI agent use this?
Yes. The same function is a tool on our free MCP server at tools.cuelark.com/mcp, so ChatGPT, Claude or Cursor get exactly the answer this page shows. 'Copy MCP call' gives you the arguments.