Is it illegal to modify a website locally
<p>I am getting flak from the company I work for for having built a bookmarklet that makes one of their web applications more functional. It injects some code and new elements onto the page to augment the features of the site. Everything it does can be reproduced in the developer console.</p>

<p>They are accusing me of violating their Terms of Service, specifically the generic phrase </p>

<blockquote>
  <p>"You agree that you will not modify, copy, distribute, transmit, display, perform, reproduce, publish, license, create derivative works from, frame in another web page, use on any other web site, transfer, or sell any information, software, lists of users, databases or other lists, products or services provided through or obtained from the site."</p>
</blockquote>

<p>Does this hold water? What I'm doing is 100% local, modifying a rendered version of a website. I am not affecting their servers in any way. How should I respond to this?</p>

<p>It's not clear exactly what you're asking, when you say "the company I work for" – i.e. are you asking "can they fire me?" (almost certainly they can, even if their TOS thinking is legally misguided – unless in your country there are laws that prevent firing employees). To be certain, you need to hire an attorney who is sufficiently savvy about web page technology that they can accurately judge what you are doing, and whether you can fruitfully resist their demands.</p>

<p>You seem to be skeptical of their position because you are "not affecting their servers in any way". The TOS is not about affecting their servers, it is about affecting their intellectual property. It appears that your code does a number of the prohibited actions such as and perhaps most importantly "modify". If you have distributed a program that allows users to modify company content on their own computers, then the user might be in violation of the TOS, but not you (since you're not running a server that redistributes). However, I am betting that in order to create and test the program you had to violate the TOS. Additionally, you could be vicariously liable for the infringements of others, especially if this program can <em>only</em> be used to infringe on copyright, and you know this fact. That is pretty much the end of the legal part. </p>

<p>As for how you <em>should</em> respond, your attorney, and not Law SE, deals in recommendations.</p>

<p>These circumstances sound very atypical. To answer your question, their claim is valid, because you are admittedly modifying their web app. But the fact that they care that you are modifying it <em>locally</em>, on your own computer, is strange.</p>

<p>Without knowing what the app does, what sort of organization you work for, and what your specific job is, there's not much more we can say, but if your bookmarklet enhances their app (and possibly makes you and others more productive) I would advise trying to get them to merge your code into the app -- if you can't convince them to let you use your bookmarklet as it stands.</p>

<p>But at the very base of the issue, the company is completely in the right (as absurd as it may seem). They own the code and they dictate the terms of its use, as well as the terms of your employment with them.</p>

terms-of-service