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Base64 Encoder & Decoder

A Base64 encoder and decoder that works with both text and files entirely in your browser. Whether you need to encode files for data URIs, decode Base64 strings back to readable text, or convert images for embedding in CSS and HTML, this tool handles it all without uploading anything to a server. Developers use Base64 encoding to embed images in stylesheets, transmit binary data over text-only protocols, and store files in JSON or XML. This tool supports encoding text to Base64, encoding files up to 10MB, decoding Base64 to text, and decoding Base64 to downloadable files with automatic MIME type detection. All processing happens client-side using native browser APIs, ensuring your data stays private and secure. Free, no signup required, and works offline once loaded.

How to Use This Base64 Tool

  1. Choose Encode or Decode using the tabs at the top
  2. For encoding, select Text or File input, then enter your text or upload a file (max 10MB)
  3. Click Encode to Base64 to generate the Base64 string, then copy it or download as .txt
  4. For decoding, paste your Base64 string and click Decode. The tool auto-detects whether it's text or a file
  5. Preview images directly in the browser, or download decoded files with one click

Why This Base64 Method?

Base64 encoding converts binary data into ASCII text using a 64-character alphabet (A-Z, a-z, 0-9, +, /). This makes it safe to transmit files over text-only protocols like email or JSON APIs. The process works by taking 3 bytes (24 bits) of binary data and splitting them into 4 groups of 6 bits, then mapping each group to a Base64 character. This btoa() and atob() browser API implementation is the standard way to encode and decode in JavaScript, with UTF-8 support via encodeURIComponent() for international characters.

Developers commonly embed small images in CSS using data URIs (e.g., background-image: url(data:image/png;base64,...)) to reduce HTTP requests. Base64 is also used to encode files in JSON payloads, store binary data in databases, and transmit images in email HTML. The 33% size increase from Base64 encoding is offset by reduced network round-trips for small assets.

This tool detects MIME types automatically by reading file signatures (magic numbers) in the decoded bytes. PNG files start with 89 50 4E 47, JPEG with FF D8 FF, and so on. This allows the tool to preview images and suggest correct file extensions for downloads without requiring the original file metadata.