I'll try to keep this short and devoid of legalese. Just take a few moments, let this notice sink in, and then choose wisely. Don't worry, I wont bite.

Third party services used by pxlsFiddle.com
This site uses third party services where explicitly mentioned - it does not use any ads, analytics services, trackers, etc. So what services does it use, why, and how might it affect your privacy?
imgur.com, an image hosting site, is used to upload images that you choose in the template styling section. imgur may receive, among other, your IP address and common browser information (browser name, version, and all that good stuff)
pxls.space, a pixel canvas site that this site is a companion to - but not affiliated with, is used if you choose to get the canvas dimensions and palette. This information is retrieved through a proxy on this site, so this should not send them any informationn about you.
pxls.space, again, is also used if you use the Avogadro project link. This link opens pxls.space in an iframe. By using its functionality, you send as much information to pxls.space as you would if you visited the pxls.space directly.
fonts.googleapis.com, a vector font repository, is used when you specify a Custom font in the text rendering section when that font is not available on your system. Google may receive, among other, your IP address and common browser information.

Cookies and Settings Storage
This site does not use cookies. This site does use Local Storage - a small amount of disk space reserved by your browser for every site. Other sites should not have access to this data, but browser flaws may exist. This data can be subdivided into two things:
template utility settings and UI states, used to store your preferences for the tempate utility's settings and user interface states. This doesn't include any personal information unless you add it yourself. If you name a layer with your real name, that's on you.
pxls.space account authentication, used to store which pxls.space account belongs to you (or details were given to you - people shouldn't do that). Depending on how you feel about your pxls.space username, you may feel like this is personally identifying.

Logging information
As part of its normal mode of operation for security - and I'm sure some asinine data-retention laws the provider adheres to - this site does log access to any and all parts of the site, which means the provider has this information as well. This log information includes your IP address. If you'd rather not have this happen, you should leave. The internet. You should leave the internet. Or at least get a VPN.

right-to-be-forgotten
This site generally doesn't remember you - all information is stored on your own computer - so there is nothing to forget.
Your browser should provide you with the functionality to remove this information, typically by searching its settings for 'cookies'. Delete the cookies/storage, and as far as this site is concerned, you are a stranger once more.

If you are one of the few, the brave, who have site layer editing privileges, your username will be stored and made public in any layers you store onto the site, just so we know who was the fool that corrupted the layers object so we can point at and make fun of them. If you want this information removed, just send me a message on Discord, and your privileges will be removed and username redacted.

If you are uncomfortable with the above, and don't use the pertinent facilities and you should still be able to use this site all the same.

Thanks for your time and your understanding!
~ CtrlZ
For more information on why more sites are bothering you about this or updated privacy policies, please see the General Data Protection Regulation legislation passed by the EU.