Base64 Encoder & Decoder

How to encode and decode Base64

1. 1

   Choose Encode or Decode

   Encode turns text or a file into Base64. Decode turns Base64 back into text or a file.

2. 2

   Add your input

   Type, paste or import text, or choose a file to encode. Paste Base64 to decode.

3. 3

   Press the button

   Check the result, then copy it or download it.

Encoding

• Text is encoded as UTF-8. Accents, emoji and other scripts are turned into UTF-8 bytes first, as most websites and APIs expect. Line breaks are encoded as the text box holds them (LF).
• Files. Choose one file of any type. Its bytes are encoded as they are; the file name is not part of the output.
• Standard or URL-safe. Standard Base64 uses + and /. Base64URL uses - and _ so the text can sit in a web address or a token. Choosing URL-safe switches the padding off, because most uses leave it out; you can turn it back on.
• Padding and line breaks. Padding adds = at the end so the length is a multiple of 4. Breaking lines every 76 characters gives the layout used in email (MIME), with LF line breaks.

Decoding

• Alphabet. Detect accepts either alphabet, but refuses text that mixes + / with - _. Choose Standard or URL-safe to be strict. Spaces and line breaks are ignored, and a data: URL prefix is removed.
• Padding. Missing = at the end is accepted and mentioned in the summary. Wrong padding, other characters and lengths that cannot be Base64 are refused, and the message says what is wrong.
• Text or file. As text, the bytes are shown only if they are valid UTF-8. Otherwise you get the file card instead, with the size, the kind of file when the first bytes show it (PNG, JPEG, GIF, WebP, PDF, ZIP or gzip), and a download with a file name you can change.
• Decoded files are not opened. The tool never shows, runs or previews a decoded file. It only gives it back to you as a download, so open it only if you trust where the Base64 came from.

Limits

largest text or file to encode

5 MB

longest Base64 text to decode

7 MB

Larger input is refused with a message rather than cut. Encoding and decoding run in a background thread (a Web Worker) so the page stays responsive. The output box shows the first 200,000 characters of a long result; Copy and Download always use all of it.

Frequently asked questions