Impressions are a metric in online marketing that indicates how often an advert or website has been displayed to a user. An impression is counted when a user sees the advert or website on their screen, regardless of whether they click on it or not.

Impressions are an important indicator of the effectiveness of advertising campaigns and provide information on how often an advert was displayed to potential customers. However, a high number of impressions does not necessarily mean that a campaign is successful or that the advert is effective. Rather, other factors such as click-through rate, conversion rate and ROI (return on investment) must also be taken into account in order to measure the success of a campaign.

Impressions can be measured in various online channels, such as search engine adverts, display adverts, social media adverts and email marketing campaigns. Impressions can be measured using tools such as Google Analytics or AdWords.