Base64 Decode
Paste a Base64 string and get the original text back instantly. Runs locally in your browser.
BASE64
Decodes Base64 back to the original UTF-8 text. Handles Unicode correctly.
How it works
The browser's built-in atob() function turns each Base64 character back into a 6-bit chunk and concatenates them into the original byte sequence. Those bytes are then handed to TextDecoder('utf-8'), which reassembles the original text including any emoji or non-ASCII characters that were UTF-8 encoded before they were Base64ed. Padded and unpadded inputs are accepted because the tool normalises the string before decoding.
Processing runs in your browser
All encoding and decoding happens inside your browser tab. Our servers are not involved at any point. You can confirm this yourselfin your browser's DevTools Network tab.
Technical specification
Base64 is specified in RFC 4648 (IETF, 2006). The encoding groups every three input bytes (24 bits) into four 6-bit values, each mapped to a printable ASCII character from a 64-character alphabet (A–Z a–z 0–9 + /). If the input length is not divisible by 3, one or two = padding characters are appended. The URL-safe variant (RFC 4648 §5) replaces + with - and / with _, making it safe for use in URLs and HTTP headers without further percent-encoding.
- Standard
- RFC 4648. The Base16, Base32, and Base64 Data Encodings
- Size overhead
- ~33% overhead (every 3 bytes becomes 4 characters)
- Alphabet (standard)
A–Z a–z 0–9 + /with=padding- Alphabet (URL-safe)
A–Z a–z 0–9 - _(used in JWTs, data URIs)
Related operations
To compute MD5 or SHA hashes from text or files, use the hash generator. For percent-encoding query strings or URL paths, try URL encode. To decode signed tokens that wrap Base64 payloads, see the JWT decoder.
Frequently asked questions
- What if the Base64 string is padded or unpadded?
- The tool handles both padded (with =) and unpadded Base64 automatically.
- Can I decode binary data?
- If the original data was binary (not text), the decoded output may look garbled. Use 'File to Base64' for binary files.
- Is this safe to use for sensitive data?
- Yes. Decoding happens entirely in your browser. Our servers are not involved at any point.
- What if I paste an invalid Base64 string?
- An error message appears below the input explaining that the value is not valid Base64. The original input is left untouched so you can fix the string and try again.