Base64 Decode

Base64 decoding returns bytes, not necessarily text. The size and hex preview describe those exact bytes. A text preview appears only when the complete result is valid UTF-8. File detection is a convenience based on recognized signatures or parseable text; it is not a malware or file-safety scan.

This decoder checks the alphabet, padding position, encoded length, and unused bits in the final character. The options make whitespace and missing-padding behavior explicit, so a value is not silently accepted under rules you did not intend. Automatic detection reports ambiguity when the input uses only characters shared by Base64 and Base64URL.

Images, PDFs, archives, encrypted data, and compressed data commonly decode to bytes that are not UTF-8. That is a valid result, not a decode failure. Review the file-signature hint and hex bytes, then download the unchanged bytes if you need to open them with an appropriate local application.

Paste the complete data:...;base64,... value. The decoder separates the media type and parameters from the payload, decodes percent-escaped payload characters, and compares a recognized file signature with the declared media type. Non-Base64 data URIs should be handled with a URL decoder instead.

Use the command appropriate for your environment when the value should not be pasted into any website:

# Linux
printf '%s' 'SGVsbG8sIHdvcmxkIQ==' | base64 --decode # macOS
printf '%s' 'SGVsbG8sIHdvcmxkIQ==' | base64 -D

Python can validate standard Base64 padding and characters explicitly:

import base64 decoded_bytes = base64.b64decode("SGVsbG8sIHdvcmxkIQ==", validate=True)
print(decoded_bytes)

• OpenSSL AES Decrypt Checker - Inspect Base64 OpenSSL Salted__ output without mistaking decoding for decryption.
• String Format Identifier - Check whether an unknown value looks like Base64, JWT, hex, PEM, or another structured format.
• Base64 Encode - Convert UTF-8 text into standard Base64.
• Base64 to Image - Preview supported image bytes after you know the payload is an image.
• Base64 to JSON - Work directly with a Base64-encoded JSON payload.
• Hash Format Identifier - Identify common encoded password-hash and digest shapes.