The UK government has unveiled a tool it says can accurately detect jihadist content and block it from being viewed.
Home Secretary Amber Rudd said she would not rule out forcing technology companies to use it by law.
Ms Rudd is visiting the US to meet tech companies to discuss the idea, as well as other efforts to tackle extremism.
Thousands of hours of content posted by the Islamic State group was run past the tool, in order to "train" it to automatically spot extremist material.
The government provided £600,000 of public funds towards the creation of the tool by an artificial intelligence company based in London.
ASI Data Science said the software is capable of detecting 94% of IS's online activity, with an accuracy of 99.995%.
Anything the software was not sure about would then be flagged up for a human decision to be taken.
It is intended to lighten the moderation burden faced by small companies that may not have the resources to effectively tackle extremist material being posted on their sites.
Similar tools in the past have been heavily criticised by advocates of an "open" internet, saying such efforts can produce false positives - and that means content that is not particularly problematic ends up being taken down or blocked.
In London, reporters were given an off-the-record briefing detailing how ASI's software worked, but were asked not to share its precise methodology. However, in simple terms, it is an algorithm that draws on characteristics typical of IS and its online activity.
In Silicon Valley, the home secretary said the tool was made as a way to Silicon Valley giants such as Facebook and Google are pouring their own resources into solving this problem, but this tool is at first intended to be used by small companies, and they may one day be forced to use it.
The Global Internet Forum to Counter Terrorism, launched last year, brings together several governments including the US and UK, and major internet firms like Facebook, Google, Twitter and others.
However, the bigger challenge is predicting which parts of the internet that jihadis will use next.
The Home Office estimates that between July and the end of 2017, extremist material appeared in almost 150 web services that had not been used for such propaganda before, reports BBC..