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I have a script which is obfuscated and begins like this:

var _0xfb0b=["\x48\x2E\x31\x36\x28\x22\x4B\x2E

...it continues like that for more then 435.000 chars (the file has 425kB) and in the end this is ing:

while(_0x8b47x3--){if(_0x8b47x4[_0x8b47x3]){_0x8b47x1=_0x8b47x1[_0xfb0b[8]]( 
new RegExp(_0xfb0b[6]+_0x8b47x5(_0x8b47x3)+_0xfb0b[6],_0xfb0b[7]),
_0x8b47x4[_0x8b47x3]);} ;} ;return _0x8b47x1;} 
(_0xfb0b[0],62,2263,_0xfb0b[3][_0xfb0b[2]](_0xfb0b[1])));

My question is: Isn't it way harder for a browser to execute that pared to a not-obfuscated script and if so, how much time I'm probably loosing because of the obfuscation? Especially the older browsers like IE6 which are really not that performant in JS must spend a lot more time on that, right?

I have a script which is obfuscated and begins like this:

var _0xfb0b=["\x48\x2E\x31\x36\x28\x22\x4B\x2E

...it continues like that for more then 435.000 chars (the file has 425kB) and in the end this is ing:

while(_0x8b47x3--){if(_0x8b47x4[_0x8b47x3]){_0x8b47x1=_0x8b47x1[_0xfb0b[8]]( 
new RegExp(_0xfb0b[6]+_0x8b47x5(_0x8b47x3)+_0xfb0b[6],_0xfb0b[7]),
_0x8b47x4[_0x8b47x3]);} ;} ;return _0x8b47x1;} 
(_0xfb0b[0],62,2263,_0xfb0b[3][_0xfb0b[2]](_0xfb0b[1])));

My question is: Isn't it way harder for a browser to execute that pared to a not-obfuscated script and if so, how much time I'm probably loosing because of the obfuscation? Especially the older browsers like IE6 which are really not that performant in JS must spend a lot more time on that, right?

• javascript
• obfuscation

Share Improve this question Follow asked Mar 12, 2012 at 3:57 MarcMarc 6,77199 gold badges5151 silver badges7979 bronze badges 2

• 4 Why not drop the obfuscated and non-obfuscated versions in a jsperf and find out? – Dagg Nabbit Commented Mar 12, 2012 at 4:00
• Because I don't have the non-obfuscated version. But thanks for the link - I will check that if I'm able to get or create a non-obfuscated version. – Marc Commented Mar 12, 2012 at 5:24

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3 Answers 3

Sorted by: Reset to default 4

It certainly does slow down the browser more significantly on older browsers (specifically when initializing), but it definitely slows it down even afterwards. I had a heavily obfuscated file that took about 1.2 seconds to initialize, unobfuscated in the same browser and PC was about 0.2 seconds, so, significant.

It depends on what the obfuscator does.

If it primarily simply renames identifiers, I would expect it to have little impact on performance unless the identifier names it used were artificially long.

If it scrambles control or data flow, it could have arbitrary impact on code execution. Some control flow scrambling can be done with only constant overhead.

You'll have to investigate the method of obfuscation to know the answer to this. Might be easier to just measure the difference.

The obfuscation you're using seems to just store all string constants into one array and put them into the code where they originally were. The strings are obfuscated into the array but still e out as string. (Try console.log(_0xfb0b) to see what I mean).

It does, definitely, slow down the code INITIALIZATION. However, once that array has been initialized, the impact on the script is negligible.

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