Base64 to File Converter

How the file type is detected

Base64 text carries bytes, not a file name. Unless you paste a data URI with a MIME type, nothing in the string says whether it holds a PDF, a ZIP archive or a sound. The tool therefore decodes the data and inspects the first few bytes, the file signature or "magic bytes" that most formats place at the very start. Because those bytes are fixed, the Base64 text of each format also starts in a recognizable way:

When the decoded file will not open

Base64 decoding is lossless, so a broken file almost always means the input was not what you expected. Check these causes in order:

• Truncated input. Log files, terminals, spreadsheet cells and chat apps often cut long strings. Missing text at the end gives a file that is too short, and most formats then refuse to open. If you know the original size, compare it with the decoded size.
• Extra characters. Quotes, commas or a field name copied along with the value, or escape sequences such as \/ and \n from a JSON string, are not part of Base64. Copy only the value itself.
• A different encoding or variant. Hex, Base32, Base85 or a custom alphabet can look similar at a glance but turn into garbage when decoded as Base64. The Base Detector tries every decoder and shows which one fits.
• Not a file at all. If the result is detected as plain text, the string was Base64 of text: JSON, a token, or another layer of Base64. Read it with the Base64 decoder, and decode once more if the output is Base64 again.

The Base64 Validator lists invalid characters with their positions and reports padding problems, which helps to locate a damaged section.

Decode Base64 to a file in code

# Python
import base64
with open('output.bin', 'wb') as f:
    f.write(base64.b64decode(data))

// Node.js
fs.writeFileSync('output.bin', Buffer.from(data, 'base64'));

# Linux
base64 -d input.txt > output.bin

# macOS
base64 -D -i input.txt -o output.bin

# Windows PowerShell
[IO.File]::WriteAllBytes("C:\files\output.bin", [Convert]::FromBase64String((Get-Content input.txt -Raw)))