Liverpool are allowing Pinnington to leave without a transfer fee, despite him being under contract at Anfield, with the deal structured around appearance-based add-ons and a sell-on clause to protect the club's long-term interest in the player.
Pinnington joined Liverpool's academy at the age of seven and signed his first professional contract with the club in May 2024, progressing through every level of the youth system to become a regular for the Under-21 side.
Crystal Palace had also expressed interest in the Wirral-born defender after he was named on the bench against them in the Carabao Cup earlier last season, but West Brom have moved quickest to secure his signature.
A versatile player, Pinnington has operated primarily as a centre-back for Liverpool's under-21s but has also featured at full-back and in a holding midfield role, with his comfort on the ball and reading of the game drawing comparisons to a classic ball-playing defender.
He is eligible to represent England through his own nationality but holds dual eligibility to represent South Africa through his father.
West Brom are also in advanced talks to sign Chelsea forward Jimmy Jay Morgan in a deal worth around £1.3 million.
Morgan, who had a spell at Southampton as a teenager, is an England Under-20 international who scored 14 goals on loan at Peterborough United in League One last season.
The Baggies believe Morgan can step up to Championship level, and the club are shaping their squad around young, high-potential players that new head coach James Morrison can develop over time.
West Brom narrowly avoided relegation to League One last season before Morrison steadied the ship with a ten-game unbeaten run.
The club confirmed him on a two-year deal and have identified this window as the moment to rebuild the squad in a way that is financially sustainable under the scrutiny of EFL regulations.
Signing Pinnington and Morgan in quick succession signals the direction West Brom intend to take.
Both represent low-cost, high-upside additions in a transfer window where the Baggies need to be shrewd rather than lavish.
For Pinnington, the move offers what Liverpool could not — regular senior football in a competitive division and the opportunity to establish himself as a first-team player at a club willing to build around him.