Base64 Validator

Paste a Base64 string to check validity, detect the variant (standard or URL-safe), see a decoded preview, and measure data size.

How to use Base64 Validator

1. Paste your Base64 string into the input box.
2. Click Validate to check if it is valid Base64.
3. Click Decode to see a preview of the decoded data.
4. Review the variant, data size, and padding details.

What is Base64 Validator?

FAQ

What is the difference between standard and URL-safe Base64?

Standard Base64 uses + and / as the 62nd and 63rd characters, while URL-safe Base64 uses - and _ instead. URL-safe encoding is used in URLs, filenames, and JWT tokens where + and / would need percent-encoding.

Why does my Base64 string show as invalid?

Common issues: non-Base64 characters mixed in, missing or excessive padding (=), incorrect length, or whitespace. Strip any line breaks or quotes and try again.

Can it decode encrypted or binary data?

Yes — the tool decodes any valid Base64. If the result is non-printable binary data, it shows the size but not the raw bytes. For binary inspection, use a hex editor.

Related tools

• Base64 Encode / Decode
• URL Encoder / Decoder
• Hex Converter