Encode plain text into Base64 or decode Base64 back into readable text instantly — all in your browser, with full Unicode support and no sign-up required.
All encoding and decoding runs entirely in your browser. No text is uploaded or stored on a server.
The Base64 Encoder / Decoder converts plain text into Base64 and decodes Base64 back into readable text instantly, right in your browser. Base64 is a binary-to-text encoding scheme that represents binary data using only 64 printable ASCII characters — the letters A–Z and a–z, the digits 0–9, plus the symbols + and / — so that data can travel safely through systems that were designed to handle text.
Base64 exists because many older protocols — email, URLs, HTTP headers, JSON fields — were built to carry text and choke on raw binary bytes. By mapping every three bytes of input into four Base64 characters, the scheme guarantees that images, encrypted tokens, certificates, and other binary payloads can be embedded inside text-only channels without being corrupted or altered in transit.
Developers reach for Base64 constantly: embedding small images directly in HTML or CSS as data URIs, transmitting authentication credentials in HTTP Basic Auth, storing binary blobs inside JSON or XML, encoding email attachments in MIME, and passing signed tokens in web APIs. This tool handles all of those workflows with full Unicode support, so emoji, accented characters, and non-Latin scripts encode and decode correctly.
Because every conversion runs locally in your browser using native JavaScript APIs, nothing you type is ever uploaded to a server, stored, or logged. There is no sign-up, no rate limit, and no waiting on a network round-trip — paste your text, read the result, copy it, and move on. The real-time conversion updates as you type, and the swap button round-trips an encoded string straight back to its decoded form in one click.
This tool uses the native browser functions btoa() and atob() for the core Base64 transform, wrapped in TextEncoder and TextDecoder so that full Unicode is handled correctly. Native btoa() only accepts Latin-1 characters, so the encoder first converts your string to UTF-8 bytes with TextEncoder, then maps those bytes to Base64. The decoder reverses the process: atob() produces raw bytes, which TextDecoder reads back as a UTF-8 string. This means emoji, CJK characters, and accented letters all survive a round-trip.
Every operation is purely client-side. The text you enter never leaves your browser — there is no fetch, no XHR, no WebSocket, and no server endpoint involved in encoding or decoding. The character and byte counts shown under each field are computed locally from the UTF-8 byte length of your input and output, so they reflect the real size of the data, not just the visible character count.
The validity check for decoding uses a strict Base64 alphabet (A–Z, a–z, 0–9, +, /) with optional = padding and a length that is a multiple of four. Whitespace is tolerated and stripped before validation. If the input fails this check or atob() throws, the tool shows a clear "Invalid Base64 string" message instead of producing garbage output, so you always know when something is wrong.