What Base64 encoding actually does
Base64 converts arbitrary binary data into a string made up only of letters, digits, and three punctuation characters (+, /, =) — a format safe to embed inside text-based formats like JSON, XML, HTML, or email, none of which can reliably carry raw binary bytes. It’s not encryption: anyone can decode Base64 back to the original data instantly, so it should never be relied on to keep something secret.
Standard vs. URL-safe Base64
Standard Base64 uses + and /, both of which have special meaning inside a URL (space and path separator context) and need percent-encoding if used raw in a query string. URL-safe Base64 swaps those two characters for - and _ instead, so the result can be dropped directly into a URL or filename — common in JWTs and API tokens — without further encoding.
Encoding files and images, not just text
Base64 is also how images get embedded directly into HTML or CSS as data URIs (data:image/png;base64,...), avoiding a separate HTTP request for small icons, and how binary attachments travel inside text-only protocols like email (MIME). This tool handles files and images the same way it handles plain text — drop one in and get the encoded (or decoded) result.
Why encode/decode locally
Base64 strings frequently contain tokens, API keys, or personal data hiding in plain sight. Decoding them in your browser instead of an unknown third-party site means that data never leaves your device.