Tool overview
What is a Base64 Encoder/Decoder?
Base64 converts binary or text into an ASCII-safe string (and back) so data can travel in JSON, URLs, or email without corruption.
Why use this Base64 tool?
Encode or decode strings instantly in the browser with UTF-8 and optional URL-safe alphabet—no paste into a random third-party server.
Key Features
Encode and decode modes, UTF-8 support, URL-safe option, instant copy, and fully local processing.
How to Use
Follow these steps to get accurate results from the tool interface above.
- Paste plain text or Base64 ciphertext into the input editor.
- Toggle Encode or Decode mode from the toolbar tabs—UTF-8 text is handled via TextEncoder/TextDecoder before btoa/atob.
- Enable URL-safe mode to replace +/ with -_ and optionally strip padding for JWT-safe tokens.
- Copy the output to the clipboard or swap input/output to verify round-trip fidelity.
- Clear the editor with the trash action—state persists in localStorage only on your device.
Base64 Encoding Matrix
RFC 4648 defines standard and URL-safe alphabets. These token shapes map to successful decode paths versus exception triggers.
| Token Type | Valid Standard Format | Malformed Input |
|---|---|---|
| Standard alphabet | SGVsbG8sIOS4lueVjA== | SGVsbG8sIOS4lueVjAMissing padding may still decode in lenient parsers but strict atob() can fail on non-multiple-of-4 lengths. |
| URL-safe variant | SGVsbG8sIOS4lueVjA | SGVsbG8sIOS4lueVjA++Mixing standard +/ and URL-safe -_ in one token produces InvalidCharacterError from atob(). |
| UTF-8 plaintext input | Hello, 世界 | Hello, �Lone surrogate code units are invalid UTF-8—TextEncoder throws before encoding begins. |
| Binary-safe decode | AQIDBA== | AQID!BA==Characters outside the Base64 alphabet trigger DOMException InvalidCharacterError immediately. |
Security Profile
All encode/decode operations execute via Web Platform APIs (btoa, atob, TextEncoder, TextDecoder) inside your browser sandbox. No ciphertext, API keys, or file contents are transmitted over the network. Optional localStorage persistence is scoped to your origin and cleared with browser data. This tool performs encoding only—it does not encrypt data or provide confidentiality.
Frequently Asked Questions
Expandable answers for common debugging bottlenecks and data privacy questions.
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Official Documentation & References
Authoritative specifications and platform documentation for this utility.