343 Industries has announced that Halo Infinite campaign co-op beta will take place from 11 July 2022 to 22 July 2022. It’s open for everyone that owns the Halo Infinite campaign or has an active Xbox Game Pass subscription.

However, in order to play the Halo Infinite campaign co-op beta, you have to first join the Halo Insider program.

Here are the full steps provided by 343 Industries:

• Step 1: Make sure you’re signed up to the Halo Insider program.
• Step 2: Ensure you have the entitlement to Halo Infinite (Campaign). (i.e. you have purchased it or have an active Xbox Game Pass subscription).
• Step 3: If you’re participating on Xbox, have the Xbox Insider app downloaded, and opt into the Network Co-Op flight program once the flight is live. If you’re playing on Steam, you’ll be sent a unique key via Halo Insider communications to download the flighting build.
• Step 4: Launch the build, party up with friends, and jump into Zeta Halo!

To access the Halo Infinite campaign co-op beta, players have to start a brand new campaign and save. The full Halo Infinite campaign will be accessible, however, via online co-op with up to four players. During this period, players will also be able to replay Halo Infinite campaign missions with a new feature — Mission Replay, which was missing from the game’s launch last year.

Players accessing the game from Steam will have only until 5 July 2022 to sign up, but there’s no deadline for those playing on PC via the Xbox app or on consoles.

Best of all, Halo Infinite will support full crossplay co-op, which means that an Xbox One player, an Xbox Series X/S user, a PC player, and someone streaming the game on their phone (via Xbox Cloud) can all play together if they want to.

Here are some more details from an interview with Halo Infinite‘s Isaac Bender (Principal Software Engineering Lead) and John Mulkey (Lead World Designer):

Mulkey: This is one of the areas I am really excited about. The goal going in was to “allow everyone to play their campaigns together.” This meant that all progress made in the game, regardless of it being through Solo or Co-Op play, would be retained. I could be playing Solo campaign, jump into a Co-Op session for a few hours, then launch back into Solo play and all the mission progress, acquired collectibles, equipment found, achievements earned, and upgrades made in either session would be intact. Gone are the days of playing someone else’s game while earning no progress.

The way we are handling this is through something we internally refer to as “No Spartan Left Behind”. When players join the Fireteam and choose their save slots to play on, the game aggregates the states of all missions across those saves and sets up a world state in which any missions completed by all Fireteam members are marked as complete while any missions not completed by all are marked as incomplete.

Isaac: You can think of this system as creating a version of the world that’s like the “lowest common denominator” (or “intersection,” if you’re into set theory) of everyone’s Campaign progress. This way, no matter what you do, no one is completing missions out of order.

What this means is that any unlocks you find in Co-Op are retained in single-player. So, if you’re having a really hard time collecting a Skull, you can get in a game with a friend, and if they collect it while you’re in that session, you’ll get it too!

The full release of campaign co-op is expected coming sometime “later this year”, perhaps as early as August 2022. It was originally supposed to be available at launch back in November 2021.