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Base64 Decoder

Free online Base64 decoder. Decode Base64 strings back to plain text instantly with Unicode support, clear error messages, and one-click copy.

Base64
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Features

Everything you need, nothing you don’t.

  • Decodes Base64 strings to plain text in real time as you type
  • Automatically strips whitespace and line breaks before decoding
  • Full Unicode and multi-byte character support
  • Clear, actionable error messages for invalid Base64 input
  • One-click copy decoded output to clipboard
  • No data leaves your browser - everything runs client-side

Related Tools

Frequently asked questions

What is Base64 decoding?

Base64 decoding reverses the Base64 encoding process - it takes a Base64-encoded string and converts it back to the original text or binary data. The input must use only the characters A-Z, a-z, 0-9, +, /, and optional = padding.

Why does my Base64 string fail to decode?

Common causes include: extra whitespace or line breaks (this tool strips them automatically), incorrect = padding, non-Base64 characters such as spaces or special symbols, and URL-safe Base64 that uses - and _ instead of + and /. Replace those characters before decoding.

What is URL-safe Base64?

URL-safe Base64 (Base64url) replaces + with - and / with _ to make the encoded string safe for use in URLs and filenames without percent-encoding. This tool decodes standard Base64. To decode URL-safe Base64, replace - with + and _ with / in your string first.

Can I decode Base64-encoded images?

This tool decodes Base64 to text. If the Base64 encodes a binary file like an image, the decoded output will contain raw binary data represented as text, which may not be human-readable. Use a dedicated binary file decoder for images and other binary formats.

What does "Invalid Base64 string" mean?

The input contains characters outside the Base64 alphabet, or the string has incorrect padding. Base64 strings should only contain letters (A-Z, a-z), digits (0-9), +, /, and optional = padding at the end.

Is Base64 encrypted?

No. Base64 is only an encoding - it provides no security or confidentiality. Anyone can decode a Base64 string without a key. If you need to protect sensitive data, use proper encryption.

How do I decode Base64 in Python?

Use Python's built-in base64 module:

import base64

encoded = 'aGVsbG8gd29ybGQ='
decoded = base64.b64decode(encoded).decode('utf-8')
print(decoded)  # hello world

For URL-safe Base64, use base64.urlsafe_b64decode() instead. For a quick one-off decode without writing code, paste the string into the tool above.

How do I decode Base64 in JavaScript?

Use the built-in atob() function for ASCII strings. For Unicode output, decode the UTF-8 bytes:

// ASCII only
atob('aGVsbG8gd29ybGQ='); // 'hello world'

// Unicode-safe
decodeURIComponent(escape(atob(encoded)));

In Node.js, use Buffer.from(encoded, 'base64').toString('utf-8').