Base64 Decoder
Decode Base64 back to plain text or JSON online, free and instantly. Paste a Base64 string and this tool converts it back to readable text in your browser — never uploading your data.
How Base64 decoding works
Decoding reverses the Base64 process: the tool validates the 64-character alphabet, restores padding when it is missing, converts the characters back to raw bytes, and then decodes those bytes as UTF-8 text.
If the resulting text is valid JSON, DataFormatter detects it and pretty-prints it automatically — handy when you receive Base64-wrapped API payloads or configuration and want to read them immediately.
How to decode Base64 online
- Open the free Base64 Decoder tool from DataFormatter.
- Paste the Base64 string you received from an API, header, or config.
- The decoded text appears instantly, pretty-printed if it is JSON.
- Whitespace and line breaks inside the Base64 are handled automatically.
When you'll need a Base64 decoder
- Reading data URIs and embedded images
- Inspecting Base64-encoded JSON from APIs
- Checking values inside JWT fragments and auth headers
- Debugging tokens and encoded configuration values
Frequently asked questions
Why won't my Base64 string decode?
Decoding requires valid Base64 characters (A–Z, a–z, 0–9, +, /) with correct padding. Invalid characters, missing padding, or data that is not valid UTF-8 text will produce an error rather than garbage output.
Can it decode Base64 that contains JSON?
Yes. If the decoded bytes are valid JSON, the tool pretty-prints it automatically so you can read the structure instantly.
Does Base64 decoding work on private or sensitive data?
Yes — everything is decoded locally in your browser. Nothing you paste is uploaded, so it is safe for sensitive payloads.