Base64 Encode & Decode
Encode or decode Base64 and URL-encoded text instantly. Supports UTF-8, large payloads, and one-click copy. Nothing leaves your browser.
What is Base64
Base64 is an encoding scheme that turns arbitrary binary data into 64 safe ASCII characters. It is everywhere: HTTP Basic auth headers, data URLs, email attachments, JWT payloads and countless API transports.
Why encode at all
Base64 is not encryption. It is a transport encoding that makes binary data safe to pass through text-only channels like email headers, JSON strings and URLs.
Common uses
- HTTP Basic Authentication —
Authorization: Basic base64(username:password) - Data URLs —
data:image/png;base64,iVBORw0... - JWT segments — the header and payload of a JSON Web Token
- Email attachments — MIME
Content-Transfer-Encoding: base64
Base64 vs URL encoding
| Base64 | URL encoding | |
|---|---|---|
| Purpose | Binary to text | Escape reserved URL characters |
| Output alphabet | A-Z a-z 0-9 + / = | %XX hex escapes |
| Size overhead | ~33% | Varies, 1–3x per char |
| Reversible | Yes | Yes |
Security note
Never use Base64 to hide secrets. It is trivially reversible without a key. For sensitive data, use actual encryption — see our password generator for credential hygiene tips.
Frequently asked questions
Is my data uploaded to a server?
No. Encoding and decoding both run in your browser using the built-in btoa and atob functions. Nothing is transmitted.
Can it handle large files?
Yes, though the browser tab will eventually hit its memory limit. For files in the tens of megabytes, command-line tools like base64 are faster.
Is Base64 encryption?
No. It is an encoding with no key, which means anyone can reverse it instantly. Use real encryption if you need confidentiality.
Why did my Base64 decode produce garbled text?
That usually means the input was plain text rather than Base64. Switch the mode selector to encode to go the other way, or check whether whitespace was stripped.
Does it handle UTF-8 characters?
Yes. Multi-byte characters are encoded correctly, so emoji and non-Latin scripts round-trip without corruption.