The intended change of policy comes after a two-day meeting of the Grand Slam Board (GSB) in London last week.
Next year's slams will retain the 32-seed format that came into effect in 2001, but from 2019 the top-ranked players may find themselves facing much tougher opposition earlier in events.
Meanwhile, participants at the 2018 Australian Open will compete under a 25-second shot clock that was trialled in US Open qualifying this year.
A GSB statement read: "It was unanimously agreed to support [the] 2018 Australian Open’s application to the ITF for a waiver of the 20 seconds between points required by the Rules of Tennis, in order to allow for enforcement of a strict 25 seconds utilising a 'serve/shot clock' system in line with that trialled at the 2017 US Open."
Another change will see players who withdraw from a grand slam on the Thursday before the main draw receive 50 per cent of the money they would have received for playing in the first round.
It is hoped this will stop players trying to get through their matches while injured and reduce the number of in-match retirements.
Players may also be fined if they compete in the first round of a slam and either retire or "perform below professional standards".