Inclusion Criteria:  ≥18 years old The subject has given written consent to participate in the study New acute onset dizziness or vertigo since ≥24 hours with pathological spontaneous or gaze-evoked nystagmus (i.e. an acute vestibular syndrome, AVS). The nystagmus as described above must be present at screening (between 24 hours and 7 days from onset) spontaneously, gaze-evoked or head-shake evoked and videofrenzel documented Screening and inclusion within 7 days of onset of continuous symptoms Symptomatic at inclusion  Exclusion Criteria:  Pre-existing vestibular disease or neurological disease anticipated to affect the ability to participate in the study or the effect of the intervention. N.B: Recurring AVS with no set diagnosis before inclusion is accepted, as is past transient neurological diseases such as TIA or migraine Inability to use the online rehabilitation tool, e.g. due to not having access to a computer, tablet or smartphone, not having access to the internet or lacking in experience with such tools Mental inability, reluctance or language difficulties that result in difficulty understanding the meaning of study participation Medical and/or physical contraindications to making the required head movements (e.g. vertebral dissection) or otherwise participating in the training and testing exercises or data collection Medication or other substance intake which can affect the ability to participate in the study or the reliability of the measurement methods. These medications include regular use of: Anticonvulsants, antiemetics/motion sickness medications, bensodiazepins, neuroleptics. Transient corticosteroid and/or antiemetic treatment related to the current vertigo is accepted.