Encode and decode Base64 without mangling a single character

Base64 is a way of writing arbitrary bytes using only 64 safe characters (A–Z, a–z, 0–9, + and /), so binary data can travel through systems built for plain text. You meet it in data: URLs, email attachments, JSON payloads that embed files, Basic auth headers and webhook signatures. It is an encoding, not encryption — anyone can decode it, so never treat Base64 as a way to hide secrets.

The browser's built-in btoa() only accepts Latin-1 characters, so anything outside that range — emojis, Devanagari, most non-English scripts — throws an error or silently corrupts. This tool first converts your text to UTF-8 bytes with TextEncoder and only then encodes, so “नमस्ते” and 🇮🇳 round-trip perfectly. Decoding does the reverse via TextDecoder.

If the input is at least 8 characters, uses only the Base64 alphabet, has a length that is a multiple of 4 and actually parses, the tool decodes it; otherwise it encodes. Short words like “cat” are technically valid Base64 by accident, which is why the minimum length exists — and you can always force a direction with the Encode and Decode buttons.

The three common causes are: a character outside the Base64 alphabet (often a stray quote or URL-safe -/_ variant), padding “=” appearing anywhere except the very end, and a length that is not a multiple of 4 — which almost always means the string was truncated in transit. The error message tells you exactly which rule failed and at which position.

The conversion runs entirely in your browser with standard Web APIs — nothing is uploaded, logged or stored anywhere, and the page works offline once loaded. That said, decoded secrets on screen are still secrets: clear the tool before screen-sharing, and remember Base64 itself offers zero confidentiality.