Encode and Decode Base64

This is the single most important thing to understand about it. Base64 exists to represent binary data using only safe printable characters so it can travel through systems that expect text — email bodies, JSON fields, URLs, HTTP headers. It provides no secrecy whatsoever. Any Base64 string can be decoded by anyone, instantly, with no key. A password stored Base64-encoded in a config file is a password stored in plain text with an extra step. If you need actual confidentiality, you need encryption, and probably a secrets manager.

Encoding uses UTF-8 bytes, so Unicode in your paste round-trips correctly. Standard Base64 uses +, /, and = padding. URL-safe mode swaps + and / for - and _, and strips padding on encode — the decoder restores padding automatically. Enable the same mode when decoding JWT segments or other URL-safe blobs.

This handles text in and out, not uploading a binary file for download. A data-URL image decodes to bytes you will not read as plain text — open it in the browser instead. If decode still fails, check for line breaks from copy-paste or a mismatch between standard and URL-safe mode.

That is the promise behind every tool here. Files are read in your browser tab, processed there, and discarded when you close it — never uploaded to our servers.