Base64 Encoder / Decoder — Free Online Tool
Encode or decode Base64 safely in your browser. UTF-8 compatible, fast, and 100% private.
About this tool
Encode text to Base64 or decode it back to UTF-8 without leaving your browser.
Useful for small payloads, data URIs, and quick debugging.
FAQ
Is encoding/decoding done locally?
Yes. Everything runs in your browser; we do not upload your data.
Does it handle UTF-8 correctly?
Yes. Text is encoded/decoded with UTF-8 to avoid mojibake.
What about URL-safe Base64?
URL-safe Base64 uses “-” and “_” instead of “+” and “/” and may omit “=”. If needed, replace “-”→“+”, “_”→“/” and add padding to length % 4 == 0 before decoding.
Is there a size limit?
Only your browser memory and performance limit very large inputs. There is no server-side limit.
Can I share a prefilled example?
Yes. Use the Share button—your input is embedded in the URL (?q=...).
How to use
- Type or paste plain text to encode, or a Base64 string to decode.
- Click Encode → (or press ⌘/Ctrl+Enter) or click ← Decode.
- Review the result above, then use Copy output.
- Use Share to copy a link with your current input prefilled.
Common pitfalls
- Invalid characters: standard Base64 allows only
A–Z a–z 0–9 + / =. Whitespace/newlines are rejected. - Length: must be a multiple of 4; padding is
=or==at the end only. - Padding in the middle: not allowed—padding can only appear at the end.
- URL-safe Base64: this tool expects
+and/, not-and_. Convert first if needed. - Encoding: we use UTF-8; binary files should be handled as bytes before encoding.
Example
hello world
aGVsbG8gd29ybGQ=
aGVsbG8gd29ybGQ=
hello world