Lando Norris ahead of Max Verstappen in first Dutch F1 practice
The Briton produced a best time of one minute 12.322 seconds at the seaside circuit west of Amsterdam with Red Bull's Verstappen second and 0.201 slower after briefly going top towards the end on a rapidly drying track.
Triple world champion Verstappen has won every race at Zandvoort from pole position since the track returned to the calendar in 2021 but the championship leader is expected to have a tougher time on Sunday.
McLaren have brought an upgraded car to start the second half of the season and Norris's form indicated that it was performing well.
The Dutch driver, who had a spin without crashing, leads Norris by 78 points in the standings after 14 of 24 races, with Sunday's race his 200th start in Formula One.
Mercedes' seven-time world champion Lewis Hamilton was third fastest, 0.684 off the pace, with Ferrari's Carlos Sainz fourth.
George Russell was fifth for Mercedes, who have won three of the last four races, ahead of Williams' Alex Albon and McLaren's Oscar Piastri, who was one of the last to post a timed lap.
The conditions meant only three drivers had posted timed laps by the halfway mark in the session but the track got busier as the weather improved.
Sauber had Ferrari reserve Robert Shwartzman replacing Valtteri Bottas for the session and the Israeli was 16th fastest.