Default language can be set on your project settings.
To use the Web SDK please install the snippet first.
It can be overridden by using:
getComplied.lang = 'en-GB'
When the popup is closed. Next time that is opened, it will change to the chosen language.

Available language codes:

Country code
German Austria - de-AU
German Switzerland - de-CH
German - de-DE
German Liechtenstein - de-LI
German Luxembourg - de-LU
English United Kingdom - en-GB
English United States - en-US
Spanish Argentina - es-AR
Spanish - es-ES
French Belgium - fr-BE
French Canada - fr-CA
French Switzerland - fr-CH
French - fr-FR
French Luxembourg - fr-LU
French Monaco - fr-MC
Portuguese Portugal - pt-PT
Portuguese Brazil - pt-BR
Romanian Romania - ro-RO