How to Obfuscate (Protect) JavaScript

How can I obfuscate (protect) JavaScript?

Obfuscation:

~~Try YUI Compressor. It's a very popular tool, built, enhanced and maintained by the Yahoo UI team.~~

~~You may also use:~~

~~Google Closure Compiler~~
~~UglifyJS~~

UPDATE: This question was originally asked on 2008, and The mentioned technologies are deprecated. you can use:

terser - more information in web.dev.

Private String Data:

Keeping string values private is a different concern, and obfuscation won't really be of much benefit. Of course, by packaging up your source into a garbled, minified mess, you have a light version of security through obscurity. Most of the time, it's your user who is viewing the source, and the string values on the client are intended for their use, so that sort of private string value isn't often necessary.

If you really had a value that you never wanted a user to see, you would have a couple of options. First, you could do some kind of encryption, which is decrypted at page load. That would probably be one of the most secure options, but also a lot of work which may be unnecessary. You could probably base64 encode some string values, and that would be easier.. but someone who really wanted those string values could easily decode them. Encryption is the only way to truly prevent anyone from accessing your data, and most people find that to be more security than they need.

Sidenote:

Obfuscation in Javascript has been known to cause some bugs. The obfuscators are getting a little better about it, but many outfits decide that they see enough benefit from minifying and gzipping, and the added savings of obfuscation isn't always worth the trouble. If you're trying to protect your source, maybe you'll decide that it's worth your while, just to make your code harder to read. JSMin is a good alternative.

Is code obfuscation really useful in javascript?

Simple obfuscation will not protect your software from being hacked. If you really want to protect your javascript, to add something that will make the life of someone who tries to steal or tamper with your software really difficult, you should check Jscrambler. I have not yet seen any solution that goes even close to the level of protection they enable you to achieve.

As for the source maps question, if you obfuscate yes you should delete them.

How to perform obfuscation of source code and protect source in electron js

tl;dr You can and it is not worth the effort. Just pack your source
into a asar file, it keeps most people away from it.
Long awnser:
Use the asar option when building your app.
Obfuscating the code with a uglyfier.
Use WASM
Language bindings to grab your data from a compiled format
neonjs for Rust
edge-js for C#
N-API, NAN for C/C++
Otherwise your files are scripts, all these steps only slow down a
attacker (Tactic of many defenses), but they will not prevent them
from accessing them. The devTools are fairly easy to get opened and
people will be able to read the code in some way, shape or form. And
if someone gets your Obfuscated code it is simple to reconstruct what
is happening (see here for reference:
https://www.youtube.com/watch?v=y6Uzinz3DRU)
If you want to protect yourself from code manipulation, there are
better ways to do it. Like Hashing, Context Isolation etc. electron
has a whole chapter on the matter.
https://github.com/electron/electron/blob/master/docs/tutorial/security.md

Is using an obfuscator enough to secure my JavaScript code?

I'm going to tell you a secret. Once you understand it, you'll feel a lot better about the fact that Javascript obfuscation is only really useful for saving bandwidth when sending scripts over the wire.

Your source-code is not worth stealing.

I know this comes as a shock to the ego, but I can say this confidently without ever having seen a line of code you've written because outside the very few realms of development where serious magic happens, it's true of all source-code.

Say, tomorrow, someone dumped a pile of DVDs on your doorstep containing the source code for Windows Vista. What would you be able to do with it? Sure, you could compile it and give away copies, but that's just one step more effort than copying the retail version. You could painstakingly find and remove the license-checking code, but that's something some bright kid has already done to the binaries. Replace the logo and graphics, pretend you wrote it yourself and market it as "Vicrosoft Mista"? You'll get caught.

You could spend an enormous amount of time reading the code, trying to understand it and truly "stealing the intellectual property" that Microsoft invested in developing the product. But you'd be disappointed. You'd find the code was a long series of mundane decisions, made one after the other. Some would be smarter than you could think of. Some would leave you shaking your head wondering what kind of monkeys they're hiring over there. Most would just make you shrug and say "yeah, that's how you do that."

In the process you'll learn a lot about writing operating systems, but that's not going to hurt Microsoft.

Replace "Vista" with "Leopard" and the above paragraphs don't change one bit. It's not Microsoft, it's software. Half the people on this site could probably develop a Stack Overflow clone, with or without looking at the source of this site. They just haven't. The source-code of Firefox and WebKit are out there for anyone to read. Now go write your own browser from scratch. See you in a few years.

Software development is an investment of time. It's utter hubris to imagine that what you're doing is so special that nobody could clone it without looking at your source, or even that it would make their job that much easier without an actionable (and easily detectable) amount of cut and paste.

obfuscation of javascript and browsers

The secret to obfuscation is the browser never "understood" the original pretty program in the first place, and in fact does not need to understand it. All it does is execute the individual bits of the program in the order the program says. This is the point of Turing machines; mere local symbol manipulation is enough to do any computation.

So, your pretty program is executed as little bits, each of which does something specific; e.g.

   x = y + z;  // sum the elements
   if (p)  q = 1; // handle special condition
   print(x+q);  // produce the answer

An obfuscator tool scrambles the names used by the bits in consistent way, and may shuffle the bits of computation about in a way that don't affect the result, e.g.,

   if (r7)  p52= 1; // handle special condition
   c17 = n9 + b12; // sum the elements
   print(p52+c17); // produce the answer

Often comments and whitespace that are key help to readability are removed:

   if(r7)p52=1;c17=n9+b12;print(p52+c17);

So when the obfuscated program is run, it computes the same results, and puts them in equivalent places.

Net result: the obfuscated program does the same thing as the original.

Yes, you need a tool to do this; you can't do this by hand to any program of any real size reliably. Good obfuscators will obfuscate javascript embedded in HTML pages directly; you don't need to do any hand cutting and pasting. They are easy find with Google; you can also find a variety of them via my bio.

Javascript minify or obfuscate code before browser loads JS

I recommend Grunt for minification and concatenation of JS files (and other types).

Complete details on how to integrate minification using grunt-contrib-uglify.

If you also desire to concatenate your files and deliver one single file, check grunt-contrib-concat.

To speed up the development you should also use grunt-contrib-watch that allows you to watch over changes to your files and run the defined tasks.

Basic setup for minification:

grunt.initConfig({
    uglify: {
        my_target: {
            files: {
                'dest/output.min.js': ['src/input1.js', 'src/input2.js']
            }
        }
    }
});

Also check out the sample Grunt-file in which you should define all your tasks.

How can I hide/protect my client-side HTML/JS code?

Obfuscation really is the best you can do... Take a look at http://www.jsfuck.com/# as Obfuscation goes its about as good as it gets as long as file size isn't a concern

let what = 1; alert(what);

becomes 26330 chars!

How can I hide or encrypt JavaScript code?

You can obfuscate it, but there's no way of protecting it completely.

example obfuscator:
https://obfuscator.io