Contact
hello@seatsolver.com. One person reads it, so a reply may take a few days.
If a spreadsheet imported badly
That is the most useful thing you can report, and the hardest to guess at from here. Send the header row and two or three rows with the names changed - that is almost always enough to reproduce it. Please do not send a real guest list; it is not needed and this site is built around never receiving one.
What counts as a bug here
A rule that was quietly ignored. A guest who disappeared from the chart without appearing in the "not seated" list. A column that was read as the wrong thing. A name that printed as question marks without the export warning you first. Anything where the tool was confidently wrong rather than openly unsure is worth an email, because every one of those is a thing this tool is specifically built not to do.
A chart you disagree with is not necessarily a bug. The solver balances several things at once and will trade a tidier room for a rule you typed. If you can say which arrangement you wanted and why, that is still useful: it usually means a weighting is wrong.
If a chart came out wrong
Say what you expected and what you got, with the number of guests, the number of tables and the rules involved. If the tool printed a message about a rule it could not satisfy, include that message: it names the guests and the rule.
Things that are not coming
Accounts, shared editing, RSVP collection and a scale drawing of your venue are all out of scope, and asking will not change that: each one needs a server, and a server would mean your guest list leaving your computer. The about page explains the trade that follows from.