submitted ucas 5mins late

Your application will be marked as late, but Universities can still consider you if They still have places available and The course hasn’t filled up yet

You could always call UCAS and confirm whether the app has been flagged as 'on time' or not. At five minutes over there is a chance either way.
Unis also often apply their own grace period so things are far from hopeless.
(Sidenote: this is why we constantly tell people not to leave it until the last day, much less anywhere near the deadline time.)

as the title said at about 3 minutes before the deadline, I was unable to use the site for a short duration, not sure if it was cuz of site traffic or my internet but submitted 5 mins late, will my app still be considered on time

Heyo!
I'm sorry to hear you had site difficulties. It may be worth contacting the UCAS team to see if it has been marked as late and if anything can be done considering the circumstance. Otherwise do not stress out too much as if a University has offers left after handling their non-late applicants, they can still offer you a place! Your application will still be considered fairly. If you do not get an offer there is also clearing which you can go through to secure a University spot, though this opens up a lot later and needs to be handled directly via the University's of choice through their helplines. Do have a ring to see if anything can be done as you may never know, particularly if UCAS are in fact at fault.

Hope that helps,
Aura (Uni of Staffs)

as the title said at about 3 minutes before the deadline, I was unable to use the site for a short duration, not sure if it was cuz of site traffic or my internet but submitted 5 mins late, will my app still be considered on time