Base64 Encode / Decode Tool

What Base64 is and when to use it

Base64 turns bytes into a limited ASCII character set so text can move safely through systems that expect plain text. That makes it useful for copied header values, configuration strings, API samples, email-style payloads, and debug output. Base64 changes representation, not secrecy, so it should never be treated as encryption.

Common workflows

Check a Basic Authorization header

A common debugging task is verifying a copied Basic Auth value. In that format, a plain text username and password are joined with a colon and then encoded as Base64. This page is useful when you need to confirm what a copied header actually contains before you send another request.

Inspect API or config values

Many systems store short text payloads, environment values, or copied sample data in Base64 form. Decoding helps you inspect what is actually present, while re-encoding lets you test small edits without reaching for another service or command-line tool.

Prepare plain text for transport

If a system expects Base64 text, you can paste readable content here and convert it before embedding it into a request, fixture, or documentation example. This tool is especially convenient for short text samples and copied snippets rather than full binary files.

Input rules and edge cases

This page is text-focused. It works well for readable strings and Unicode text, and the decoder ignores spaces and line breaks in the pasted Base64 input. Standard Base64 is expected here, so URL-safe variants that use different characters may need to be converted first. Padding also matters: missing or damaged equals signs can cause decode failures.

Why decoding fails

Decode failures usually mean the pasted value contains non-Base64 characters, incorrect padding, a truncated string, or a Base64URL variant that was copied into a standard Base64 decoder. Another common source of confusion is decoding valid Base64 that represents binary data instead of human-readable text.

Privacy and offline use

Because ToolMill runs in the browser, you can inspect copied tokens, headers, config snippets, and short payloads without sending them to another website. That is especially useful when the text contains internal values you would rather keep local while debugging.