TL;DR
Google still gives you warranty, at least if you reinstall the stock Google Pixel OS, but it is unsure if it's guaranteed. They do suggest not doing this due to device malfunctions.
Full transcript
Chat transcript for case: 0-0000000000000
Jan 7, 3:01 PM (Pacific Time)
3:02:02 PM Charles: Charles joined the conversation
3:02:03 PM Rory: Rory joined the conversation
3:02:08 PM Rory: Welcome! Your Case ID is 0-0000000000000. Refer to this if you need to contact us again.
3:02:32 PM Charles: Hi
3:03:07 PM Rory: Hi! I'm Rory and glad to help. Based on your query, you are concerned if installing a custom ROM/OS and/or rooting will void a Pixel's warranty. Let me check the details for you. Is there anything else I can help you with?
3:03:22 PM Charles: No, I think that's all I need.
3:05:56 PM Rory: Thank you for confirming
3:08:48 PM Rory: Unfortunately, my expertise is limited to Google store order management and presales. We have a dedicated team, who will be able to assist you further. allow me 3-5 minutes while transferring to a dedicated team.
3:09:11 PM Charles: OK.
3:09:32 PM Rory: Rory added participant(s): Kim
3:09:33 PM Kim: Kim joined the conversation
3:09:37 PM Rory: Rory left the conversation
3:10:01 PM Kim: Hi, welcome. My name is Kim. I can see that you are in the previous interaction, please allow me 3-5 minutes so that I can be up to speed.
3:12:25 PM Kim: Thank you for staying connected.
3:13:34 PM Kim: I can see that you are concerned if installing a custom ROM/OS and or rooting the device will void a Pixel's warranty, is this correct?
3:13:42 PM Charles: Yes
3:15:02 PM Kim: Thank you for confirming.
3:15:09 PM Kim: Before we proceed, can I please get your active phone number just in case we need to reach you out for additional information? Please be informed that our call may come from an unrecognized number or international number.
3:15:54 PM Charles: OK, is there a safe way I can tell you that?
3:16:42 PM Kim: I'm sorry, I didn't quite get that sir. May I know what you mean?
3:16:47 PM Charles: It
3:16:59 PM Charles: 's just because I don't know if this chat is secure.
3:19:07 PM Kim: I appreciate your concern, and I completely understand any hesitation you may have regarding sharing your data. I want to assure you that your data's safety is our top priority.
3:19:18 PM Charles: OK, do you still need it?
3:19:31 PM Kim: Yes please.
3:19:42 PM Charles: 1 472 743 6367.
3:20:13 PM Kim: Thank you for providing the information. Please be informed that our call may come from an unrecognized number or international number.
3:21:09 PM Charles: So is this chat being transferred to a phone?
3:22:18 PM Kim: No it is not that case sir, it's just that if in case that our chat get disconnected, we might call you for a follow up on your case or email you instead, so that is why we are asking for your active number.
3:22:46 PM Charles: Oh. OK, just to make sure, we're talking about the warranty for the custom ROM/root.
3:24:37 PM Kim: Yes, to answer that, I believe that it will not void your warranty.
3:25:11 PM Charles: From what I've read online, you would have to erase all the partitions and go back to the Google Pixel OS.
3:27:07 PM Kim: I see.
3:28:10 PM Charles: So basically as long as the phone isn't warning you about a custom OS, I think they allow it.
3:29:22 PM Kim: Yes, that is correct. But please do understand that if you change the operating system on purpose, you can continue using your device. But you acknowledge that your device might not work properly and your data could be exposed to corruption and security risks.
3:29:40 PM Kim: But I am certain that the warranty will not be voided just for that.
3:29:48 PM Charles: OK. That's all. Thank you!
3:29:57 PM Kim: You're welcome.
3:30:14 PM Charles: Is there a way to properly close the chat? I am in the popup mode.
3:30:14 PM Kim: I hope I was able to answer all your questions today.
3:30:57 PM Charles: Oh, I see it.
3:31:04 PM Charles: Charles left the conversation
3:31:05 PM Charles: Charles ended the conversation