BYTETOOLS

Base64 Decoder

Decode Base64 to readable text or download it as a file. Handles URL-safe base64url and missing padding automatically. Free, private, in-browser decoder.

What is the Base64 Decoder?

The ByteTools Base64 Decoder converts a Base64 string back into readable text or the original file. It automatically accepts the URL-safe base64url alphabet, ignores whitespace and line breaks, and fixes missing = padding, so strings copied from JWTs, emails or logs decode without fiddling.

  • Accepts standard and URL-safe (base64url) alphabets
  • Auto-fixes missing padding and strips whitespace
  • Detects binary payloads and offers a file download
  • Clear error messages for invalid Base64
  • UTF-8 safe — decodes emoji and international text correctly
  • 100% client-side and private

How to use the Base64 Decoder

  1. 1

    Paste your Base64 string into the input box — URL-safe and unpadded strings are fine.

  2. 2

    The decoded text appears instantly below.

  3. 3

    If the payload is binary, click 'Download as file' to save the original bytes.

  4. 4

    Use the Copy button to grab the decoded text.

About the Base64 Decoder

The ByteTools Base64 Decoder converts a Base64 string back into readable text or the original file. It automatically accepts the URL-safe base64url alphabet, ignores whitespace and line breaks, and fixes missing = padding, so strings copied from JWTs, emails or logs decode without fiddling.

If the decoded bytes are not valid UTF-8 text — for example an encoded image or ZIP archive — the tool detects that and offers a 'Download as file' button instead of showing garbled characters. Invalid input produces a clear error message rather than silent corruption.

Decoding happens entirely in your browser; the string never touches a server. That makes it safe to inspect tokens, config values and other sensitive payloads.

Frequently asked questions

How do I decode a Base64 string to text?

Paste the string into the decoder and the plain-text result appears instantly. The tool converts the Base64 back to raw bytes and interprets them as UTF-8, which covers virtually all modern text including emoji and non-Latin scripts.

Why does my Base64 string fail to decode?

Usually the string contains characters outside the Base64 alphabet, was truncated, or is actually something else (like hex). This tool already tolerates missing padding, line breaks and the URL-safe alphabet, so a failure typically means the string is genuinely corrupted or incomplete.

Can I decode Base64 back into a file like an image or PDF?

Yes. When the decoded bytes are not readable text, the tool detects it and offers a download button so you get the original binary file back — for example a PNG from a data URI or an attachment from an API response.

What's the difference between Base64 and base64url?

They encode identical data but base64url swaps + for - and / for _ so the string is safe inside URLs and filenames, and it usually omits = padding. This decoder accepts both automatically, so you don't need to convert first.

Is it safe to paste tokens or secrets into this decoder?

Yes — decoding runs entirely in your browser with JavaScript and nothing is transmitted or logged. Still, treat decoded secrets carefully once they are on your screen or clipboard.

Guides for Base64 Decoder

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