[2] He attended Shirley Boys' High School and left before finishing his final year, proceeding directly to the University of Canterbury to study law.

[4] Webb has also worked for the Public Interest Project, which seeks to get innocent people out of jail, and for the Howard League, which promotes prisoners’ rights.

In Webb's first term of Parliament, he served on various select committees including Regulations Review (2017–2020), Foreign Affairs, Defence and Trade (2017–2018), Justice (2018–2019), Finance and Expenditure (2017–2020) and Environment (as chair, 2019–2020).

[11] During the 2020 New Zealand general election, Webb was re-elected in Christchurch Central, defeating National candidate Dale Stephens by 14,098 votes.

[22][23] Webb was re-elected in Christchurch Central for a third time in October 2023, defeating Dale Stephens by a decreased margin of 1,841 votes.

[29] Webb has also defended the Boycott, Divestment and Sanctions campaign as a form of non-violent protest against Israeli policies towards the Palestinians.

[30] In early June 2018, Webb also presented a petition on behalf of Palestinian solidarity activist Donna Miles that asked Parliament to request the New Zealand Superannuation Fund to divest from "illegal" Israeli settlements in the West Bank.

[31] In August 2018, Webb hosted a meeting with Unite Union Director Mike Treen, who participated in the International Freedom Flotilla's attempt that year to breach the Israeli blockade of the Gaza Strip.

"[38] In early August 2024, Webb attracted controversy after posting an Instagram video where he spoke at a rally where protesters chanted "Hey, Luxon, what do you say?

Webb also gave a speech denouncing the "demonisation" of Palestinians, alleged "Israeli apartheid," and calling for an end to the Israel-Hamas war.