At the moment, Instagram users see a running total of people who have liked a post. In the trial, users will see a user name "and others" below posts.
Instagrammers can still view the number of likes their own posts receive.
There is concern social media platforms can contribute to low self-esteem and feelings of inadequacy in young people.
Instagram launched a similar trial in Canada in May and the new test is rolling out in Australia, New Zealand, Ireland, Italy, Japan and Brazil, the company told the BBC.