People are posting the squares to take part in the Blackout Tuesday movement, which began in the music industry. Artists pledged not to release new music or post to social media for a day to commemorate George Floyd. TV stations and radio channels also got involved by holding on air silences.
Others then hopped on the trend by posting the black squares to Instagram and committing to not post again for the rest of the day. This appears to be an unintended offshoot from the original Blackout Tuesday campaign which was aimed at making space for an "honest, reflective and productive conversation" about the collective action needed to "support the Black community".