Good reproduction is key for successful dairy farming. Detection of estrus is the first step in getting a cow pregnant. Visual detection of estrus is a challenging job, to aid the farmer, estrus detection tools (EDT), such as pedometers, neck mounted collars to measure activity and pressure sensing devices to measure standing estrus, have been developed. EDT have proven useful in practical dairy farming, however, studies from the last five years reveal a great variation in sensitivity, specificity and positive predictive values. In research, the standard that is used to define a true estrus period can affect the performance of the EDT under investigation. Cow factors that can affect performance of EDT are number of ovulation after calving, milk production, lactation number, body condition score and lameness. The second step in getting a cow pregnant is insemination at the correct time. With EDT it is easier to determine optimal insemination time, which is 12 to 24 h before ovulation. The optimal time interval in which to inseminate seems to be about 5 to 17 h after an increase in activity as measured by pedometers or neck mounted collars. Novel measurements, such as rumination time, eating time, lying behavior, ultra-wide band technology to measure mounting and standing-tobe-mounted behavior and infrared thermography to measure temperatu