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Base64 Encoder / Decoder

Encode any string or file to Base64 (or Base64URL) and decode it back. Useful for inspecting auth headers, embedding payloads, decoding JWT parts, or debugging quoted-printable email content.

⚡ Client-side only 🔒 Files never uploaded 🌐 Unicode-safe (UTF-8) ✓ Standard + URL-safe

Plain text input

Base64 output

Type in the input panel — output regenerates instantly.

Base64 vs Base64URL

Standard Base64 uses A-Z a-z 0-9 + / and pads with =. That alphabet breaks when the output goes into a URL, filename, or HTTP header because +, /, and = have reserved meanings. Base64URL (RFC 4648) replaces + with -, / with _, and usually omits the trailing = padding entirely. JWT tokens use Base64URL.

Unicode handling: the browser's built-in btoa() only works on Latin-1 (8-bit) strings, so non-ASCII characters cause "InvalidCharacterError". This tool encodes the input as UTF-8 bytes first (via TextEncoder), so any Unicode text round-trips correctly. Try pasting some emoji — they encode cleanly.