From the FAQ, they do not respect robots.txt since they only archive on request by a user and they do not remove archives unless they contain illegal content.
There is also the issue of EDNS subnet.^3 archive.is tries to require it; it wants to know what location a request is coming from. In addition to EDNS, archive.is inserts the IP address and geolocation of the incoming request into the HTML of the returned page as a tracking pixel.^4
Thus archive.is does some things archive.org does not do besides just ignoring robots.txt
One of the things archive.org does that archive.is does not do is that archive.org inserts an HTTP response header intended to disable Chrome FLoC.^5 I add this header for all sites in a local proxy; however I do not see many sites adding it as a courtesy. Thanks archive.org for doing that.
1. https://en.wikipedia.org/wiki/Archive.is
2. https://www.reddit.com/r/KotakuInAction/comments/3e29vm/arch...
3. https://webapps.stackexchange.com/questions/135222/why-does-...
4. https://news.ycombinator.com/item?id=27498902
5. permissions-policy: interest-cohort=()
https://github.com/ArchiveBox/ArchiveBox/wiki/Web-Archiving-...