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// Encoding

Base64 Encoder / Decoder online

Encode text or files to Base64, decode Base64 strings — runs in your browser

Base64 Encoder / Decoder logo
by
CHUNKY
MUNSTER
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How to Use base64

  1. Paste text or a data string into the input field.
  2. Click Encode to convert to Base64, or Decode to recover original text from a Base64 string.
  3. For files, switch to File mode and drag a file to generate a data URI.
  4. Copy the output directly — no download required for text.

Base64 is the lingua franca for safely embedding binary data in text contexts: email attachments, JWT payloads, data URIs, API tokens, and cookie values all rely on it. This tool handles both text-to-Base64 and file-to-Base64 in one place, with support for URL-safe encoding and data URI generation — everything happens locally in your browser.

Text vs File Encoding

Text encoding converts your string's UTF-8 bytes to Base64. File encoding reads the file's raw bytes directly and produces a Base64 string or a complete data URI (data:image/png;base64,...) that can be embedded in HTML, CSS, or JSON. Data URIs let you include images and fonts in HTML without separate HTTP requests — useful for small assets but impractical for large ones due to the 33% size overhead.

Frequently Asked Questions

What is a Base64 data URI?

A data URI has the form data:[mediatype];base64,[encoded-data]. You can use it anywhere a URL is expected in HTML or CSS — for example as an img src or a CSS background-image. No separate network request is made.

Can I decode an image data URI back to a file?

Yes. Paste the data URI, click Decode, and download the resulting binary content as a file. The tool strips the data:...;base64, prefix before decoding.

What is the expansion factor of Base64?

Base64 produces roughly 4 characters for every 3 bytes of input — a 33% overhead. A 1 MB file becomes approximately 1.33 MB Base64.

Can I use Base64 to pass binary data in a JSON API?

Yes — JSON only supports strings, numbers, arrays, and objects. Binary data must be serialised as a Base64 string to be valid JSON. This is the standard approach for APIs that exchange binary blobs.

See also File to Base64, ASCII85, and the Base32 tool for related binary-to-text encodings.

📖 Reference: RFC 4648 — The Base16, Base32, and Base64 Data Encodings