You are replaying it in your head on the walk home, and you will keep replaying it for days. That is normal, and this article is partly here to talk you down from it, because the honest answer to "how do I tell if it went well" is: less reliably than you would like, and you should be careful about how much weight you put on any single sign.
Still, some signals are more meaningful than others, and knowing which is which can save you from reading disaster into a perfectly good interview, or false hope into a polite rejection-in-waiting. So here is an honest sort of the reliable signs from the ones that feel meaningful but are not.
The signs that genuinely mean something
The conversation ran long. If a thirty-minute interview became forty-five because the discussion kept going, that is a real signal. Interviewers protect their time. They do not overrun for candidates they have already ruled out. This is one of the more trustworthy indicators.
They started selling the role to you. When an interviewer shifts from assessing you to persuading you, talking up the culture, the progression, the team, the perks, unprompted, it often means they have mentally moved you into the "want" column and are now worried about losing you. The direction of persuasion flipping is a good sign.
They talked about specifics of you starting. Discussing when you could start, how the onboarding works, introducing you to someone else on the team, or getting into concrete next steps with real dates, all suggest they are picturing you in the role rather than just interviewing you for it.
They engaged with your answers rather than just collecting them. An interviewer who follows up, challenges, builds on what you said, and treats it as a conversation is usually more interested than one who works methodically through a list and ticks boxes. Engagement is harder to fake than politeness.
Your questions sparked a real discussion. If the "do you have any questions" section turned into a genuine back-and-forth rather than short factual replies, that is a good sign the rapport was real.
The signs that feel meaningful but are not
They were friendly and smiled a lot. Some interviewers are warm with everyone, including candidates they are about to reject. Others are reserved with people they are about to hire. Warmth tells you about their personality far more than about your chances. Do not bank on a smile.
They said "we'll be in touch soon" or "you did great". These are often just polite closings, said to nearly everyone, and mean almost nothing about the decision. Reading a job offer into a courteous sign-off is how people set themselves up for a painful surprise.
It "felt" good or bad. Your emotional read of an interview is one of the least reliable signals there is, because it is heavily distorted by your own nerves. People routinely walk out convinced they bombed an interview they actually aced, usually because they are fixating on one clumsy answer the interviewer has already forgotten. The opposite happens too. Your gut is not a good predictor here.
A tough interview means it went badly. Often the reverse. A rigorous, challenging interview frequently means they are taking you seriously as a real candidate and want to be sure. An easy, pleasant chat can mean they had already decided, in either direction. Difficulty is not a verdict.
One bad answer. You will remember the question you fumbled far more vividly than the interviewer will. A single weak answer in an otherwise solid interview is rarely decisive, and you are almost certainly weighting it far too heavily on that walk home.
Why you should hold all of this loosely
Here is the uncomfortable truth underneath all of it: you have very limited visibility into the decision, because most of what determines it happens after you leave the room and has nothing to do with you. There might be an internal candidate. There might be five other strong applicants you never saw. The budget might change. The role might get put on hold. None of that shows up in any signal you can read on the day.
So the healthiest stance is to read the signs for interest, not for the verdict, and then genuinely let it go. Obsessing over the tea leaves does not change the outcome, and it makes the wait miserable. The interview is over. The most useful thing you can do with the energy is put it into the next one, or into a good follow-up message, which is one of the few things still in your control.
The one thing worth doing afterwards
While it is fresh, write down the questions you were asked and how you felt your answers went, honestly. Not to torture yourself, but because it is the best raw material you have for improving. The questions that caught you off guard are exactly the ones to prepare properly before your next interview, whether that is with this employer at a later stage or somewhere else entirely.
If you found yourself stumbling on the behavioural questions, that is the most fixable thing there is, and the fix is not reading more, it is rehearsing. You can practise the exact questions that caught you out and get feedback on the answers, so that next time the walk home is a lot quieter.