CodesBeautify

Base64 to Javascript Converter

Decode Base64 into readable JavaScript, a string literal, or a snippet that decodes at runtime.

Base64
JavaScript
Runs locally in your browser

About the Base64 to Javascript Converter

Encoded scripts show up in obfuscated bundles, in bookmarklets, in analytics tags and in data:text/javascript URIs found while auditing a page. Reading them is the first step of working out what they do, and that is what the default mode gives you: the original source, with JavaScript syntax highlighting and a count of the function definitions it contains.

The string literal mode wraps the decoded text in a properly escaped JavaScript literal, quotes, backslashes, newlines and all. That saves the fiddly manual escaping when you need to embed a script as data inside another script, or drop a fixture into a test file.

The loader mode goes the other way. Instead of decoding for you, it emits a short snippet that carries the Base64 as a wrapped string constant and decodes it at runtime with atob and a TextDecoder. The variable name is yours to choose. This is the pattern used when a payload needs to survive a build step or a template engine that would otherwise mangle its punctuation, and the wrapped concatenation keeps every line under a sensible width.

Decoded code from an unknown source should be read, never pasted into a console: atob only decodes, but running the result executes whatever it contains. To go the other way use JavaScript to Base64, and JavaScript Beautifier will reformat a minified result.

How to use

  1. Paste the Base64 into the left pane, with or without a data URI prefix.
  2. Keep Result on decoded source to read the script.
  3. Switch to the loader mode and set a Variable name to generate a runtime decoder instead.
  4. Copy the output or download it as a .js file.

Common questions

Is it safe to decode a script I do not trust?
Decoding is safe because nothing is executed. Reading the result is fine, running it is not.
The decoded code is one long line. Can I format it?
Yes, paste it into JavaScript Beautifier, which restores indentation and line breaks.
Why does the loader use atob rather than Buffer?
The snippet is written for the browser. In Node you would use Buffer.from with the base64 encoding instead.
What if the payload is not text at all?
You will get an error saying the bytes are binary. Use the loader mode, which works with any payload, or save it as a file.