Matches in the qualifying phase may be played in daylight or under floodlights. If played under floodlights, the illuminance must correspond to the requirements set in the UEFA Stadium Infrastructure Regulations.
From the group stage onwards, the average level of horizontal illuminance must be at least, 1,400 Eh (lux) and the uniformity ratios must be U1 > 0.5 and U2 > 0.7. The average level of vertical illuminance must be at least 1,000 Ev (lux) and the uniformity ratios must be U1 > 0.4 and U2 > 0.5. All glare ratings (RG) must be less than 50. The pitch illuminance levels should have a colour rendering (Ra) of at least 80.
Clubs must ensure that floodlighting installations are maintained and provide UEFA with a valid lighting certificate issued within the previous 12 months. UEFA may conduct an independent assessment of lighting levels in stadiums and will notify the clubs in good time of the results of such assessments and of any corrections to be made.
Full floodlighting must be provided from four hours before kick-off on matchday, or at the latest in time for the start of the GLT calibration test, unless otherwise approved by UEFA. Furthermore, use of LED floodlight entertainment may be permitted subject to the agreement of, and according to principles determined by UEFA. Any such lightshows must take place either before warm-up or between warm-up and players leaving the tunnel for the match. No lightshows may take place once any players (including goalkeepers) are on the field to warm up before the match, or once players leave the tunnel for the pre-match line-up.