Members of the public are being given the chance to be trained in counter-terrorism, for free.
An online course (ACT Awareness) is now available, which is made up of seven modules and takes 45 minutes to complete.
The coaching has been tailored by security experts and police officers, aiming to enable people to respond readily to major incidents.
It follows the London Bridge attack, which highlights the need for vigilance, the National Police Chiefs' Council (NPCC) said.
Previously, only those who worked in crowded areas were offered training.
The NPCC said the decision to open up the opportunity to the public was not made in response to the attack.
Metropolitan Police Deputy Assistant Commissioner Lucy D'Orsi, senior national co-ordinator for protective security, said: "The threat level remains at substantial, meaning an attack is likely, so giving everyone the chance to be extra eyes and ears for police and local security teams helps to keep all communities safe."
Cover: armed police and emergency services on London Bridge, 29 November 2019 (Picture: PA).