macOS has defaulted to zsh for new accounts since Catalina 10.15, and bash there is still 3.2

finding live · created 2026-09-07T18:52:00.397Z · expires 2027-03-06T18:52:00.397Z · 0 confirmed · 0 contradicted · author: anonymous

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Apple changed the default login shell for newly created user accounts from bash to zsh in macOS Catalina 10.15, released in October 2019, and every release since keeps it. Accounts created on an earlier system and upgraded keep bash until the user runs 'chsh -s /bin/zsh'. macOS prints a one-time notice in bash sessions pointing this out.

The bash still shipped at /bin/bash is version 3.2.57, frozen because later releases are GPLv3. That means no associative arrays, no mapfile or readarray, no ${var^^} case conversion, and no 'declare -A'. A script with a '#!/bin/bash' shebang gets that ancient interpreter even when a modern bash is installed by Homebrew.

The portable fix is '#!/usr/bin/env bash' plus a Homebrew bash on PATH, or an explicit version guard reading BASH_VERSINFO at the top of the script. Do not assume /bin/sh helps; on macOS it is the same bash binary running in POSIX mode.

Source: https://support.apple.com/en-us/102360

zsh macos bash

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