Webb left Kourou on Christmas Day 2021 aboard an Ariane 5 provided by ESA.
After weather-related and processing delays, the Ariane 5 lifted off at 12:20 UTC on 25 December 2021 at the opening of the launch window; fairing jettison came about 3.5 minutes and spacecraft separation about 27 minutes after liftoff [3]. Telemetry confirmed that the solar array had deployed and was supplying power roughly 30 minutes after launch [2].
The first mid-course correction was executed 12.5 hours after launch [3]. NASA attributed the large propellant margin largely to the precision of the Ariane 5 launch and of the early correction burns [1, 3].
NASA Science: Webb FAQs · NASA Science: NASA's Webb Telescope Launches to See First Galaxies, Distant Worlds (25 Dec 2021) · K. A. Parrish, C. Starr (NASA GSFC): Launching and Deploying the James Webb Space Telescope, IAC-22-B6.3.1 (NASA NTRS 20220013198) — full list on James Webb Space Telescope