E3 viewership was at an all-time high this year, at least on Twitch. Official numbers released by the platform show that a record-breaking 2.9 million concurrent viewers tuned into Twitch at one point on June 10.
The previous record for total concurrent viewership on Twitch was 2.5 million, and was set in January of this year.
The Twitch infographic does not go into detail on the time frame in which this new record was set, but presumably the 2.9 million concurrent viewers tuned in during either Microsoft or Bethesda's E3 press conferences that day.
In addition, viewers watched over 1.6 billion total minutes of related Twitch content during E3, a 106.6% increase year over year. The average viewer watched 75.8 minutes of E3 content. In total, Twitch reports 97.6 million total views and over 21.2 million uniques during E3, though it's not clear if that was for E3-related content only or across all Twitch channels.
Twitch's E3 data covers the period from June 10-14, notably excluding any Twitch coverage of EA Play on June 9.