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How to use the Base64 Encode / Decode
- 1Choose Encode or Decode.
- 2Paste text, or drop a file to get its Base64 data URI.
- 3Copy the result.
What is Base64?
Base64 represents binary data using 64 printable characters (A–Z, a–z, 0–9, + and /). It is used to embed images in HTML/CSS, send attachments in email, and put binary data inside JSON or URLs. Encoded data is about 33% larger than the original. URL-safe Base64 replaces + and / with - and _.
Where you'll see Base64
- Data URIs: small images embedded directly in HTML or CSS (data:image/png;base64,…).
- Email attachments: MIME encodes attachments as Base64.
- JSON Web Tokens (JWT): the header and payload are Base64URL-encoded, so anyone can decode and read them.
- HTTP Basic authentication sends username:password as Base64, which is why it must only be used over HTTPS.
Size overhead
Base64 turns every 3 bytes into 4 characters, so encoded data is about 33% larger than the original. That is fine for small icons and tokens but wasteful for large files. Base64URL replaces + and / with - and _ so the result is safe inside URLs.
Frequently asked questions
Is Base64 encryption?
No. Base64 is an encoding, not encryption: anyone can decode it. Never use it to protect secrets.
Is my data sent anywhere?
No. Encoding and decoding happen in your browser.