As someone who's been on the hiring side there are some legalities involved on what to answer here. But I've always made a point of telling people who asked why. However I'm not in HR, so lots of people might get filtered before I even got a chance to interview them.

Also we asked candidates to do a take home and we talked about their solution during the interview, so most people got a good understanding of why they were rejected, but a couple of times people asked afterwards and I replied to them with the reasons we considered they were not at the level we were looking for, but that we would keep them in consideration for a more junior role if there ever was an opening.

Life is all about probabilities, you can do everything right and still lose (however doing everything"right" is nigh impossible). You lose if they have a better candidate, you lose if their department is suddenly not in need of the position, etc.

With that mentality, I don't bother with CVs, and just use the time saved to apply to more jobs or maybe some kind of relevant project.

Send out so many applications and keep busy, so that every response is a surprise. Only after a response can you set a reminder to reach out after a week. After a reminder, send a message and do not set a reminder. Keep applying to other jobs.

I just lose track of jobs I applied to in my head. If they aren't responding, they don't care and neither should you.

Oh God it was such an onslaught on my self image and psychology. I believe humans aren't equipped to handle the amount of rejection you have to receive during that grind. I certainly wasn't.

There’s actually multiple questions here.

The hiring process has an application “filter” layer, a candidate selection layer, and THEN the interview with the person/people who actually want to hire you. Sometimes there’s an extra technical interview after that.

These days, the filter layer is mostly automated. Asking the filter why it didn’t select you is like asking a Machine Learning model why it chose to do something a certain way — you aren’t going to get a useful response.

So the only way to figure it out is trial and error: vary your application in terms of structure and content until you find the combination that makes it last the current batch of filters.

OR

Find a way to skip the filters altogether by finding someone on the inside of the company to flag up your CV to the people looking to fill the position.

Once past the filter, you get to HR, and if you get this far, asking questions about why you didn’t get selected to continue will actually be met with a useful response (unless it’s a company you don’t want to work for). HR will tell you the basic things they’re looking for in an application, and possibly how you compared in certain criteria to the stronger candidates.

Next you get to the manager. If you get this far, you can usually have this discussion at the end of your interview. They’re looking for fit for the role, and you can ask questions about fit as part of the interview process.

And finally you get to the technical interview. If you get this far and don’t get the job, the reason why is usually fairly obvious: either they had someone who was both a better fit AND understood the problem domain / demonstrated an ability to learn and reflect the team culture better, or you failed to prove technical ability in a key area.

Something I picked up over the years. The reasons are potentially personal or emotional.

Skills, experience and education are important.

But they are also concerned with cohesion.

"Is this someone I can have a beer with and have a good time"

"Will this person enjoy the company of the staff under my charge"

"That guy drove in with a insert political message on their bumper sticker. :/"

"Gross they used random font"

"We got too many Marks at this company"

I mean what else can you do?

how do I accept I'll never know why any employer rejected me?

Ask yourself if it was ever a real job offer to begin with. Did you have the required skills? Were your pay requirements reasonable? (For YOU not them). Then you did fine.

The same way you get over not knowing just about anything else.

Let it go.

Does it serve you in any way to continue to be bothered by not knowing?

You are irrelevant to them. Just like I'm irrelevant to you. That's life.

the good news is it's very easy to get some practice

try a DBT program xd

Shiit so many comments here.

If you are distressed by anything external, the pain is not due to the thing itself, but to your estimate of it; and this you have the power to revoke at any moment

If you are based in Europe you could always try a GDPR subject access request to see the notes they've taken. Not sure if you can try something like that wherever you are though!