Base64 Decoder reverses RFC 4648 Base64 back into the original text or binary. It automatically detects and accepts both the standard alphabet (`A–Z a–z 0–9 + / =`) and the URL-safe alphabet (`- _`) used in JWTs and OAuth flows, and it tolerates missing `=` padding so unpadded URL-safe strings decode correctly. Whitespace, newlines, and PEM-style `-----BEGIN/END-----` headers are stripped before decoding. The decoder uses `TextDecoder("utf-8")` on the resulting bytes, so multi-byte characters like `€` or emoji come out intact. Malformed input (invalid characters, wrong length) surfaces a clear error rather than silently producing garbage. All decoding runs in your browser, which means you can safely paste tokens, credentials, or sensitive JWT payloads without uploading them.
Free, fast, and runs entirely in your browser — no signup, no upload to a server.