What Happens in Swarm Simulator While You Are Away?

When you return to Swarm Simulator after closing it, the game shows a "Welcome back!" message that tells you how long you were gone and what your swarm produced in that time. This works because the game saves your progress in browser storage (cookies/localStorage), so it can compare your last session against the current time and credit you with offline production.

What the welcome-back message shows

On return, a popup displays three pieces of information:

• A greeting: "Welcome back!"
• Time away: the duration since you last closed the game, shown in human-readable form (for example, hours or days).
• Offline gains: the amount your swarm produced while you were away, displayed with a number and the matching unit type (such as larvae or meat).

The message is informational — it reports what already happened rather than asking you to claim anything.

Why offline progress depends on saved data

The offline calculation only works if the game can read your previous save. That save lives in your browser's cookies/localStorage. If that storage is unavailable, the game cannot tell when you last played or what you had, so the welcome-back summary won't appear correctly.

The game's own error messages describe the common failure: the site needs permission to set cookies/localStorage, and the problem "usually happens when your browser is blocking third-party cookies." In that case you may see a loading error instead of your progress.

If the welcome-back message doesn't appear

1. Check cookie/storage settings for the site. Allow cookies and local storage for swarmsim.com, including third-party cookies if your browser blocks them by default.
2. Use a supported browser. The game states it does not support Safari and recommends Chrome or Firefox if you have trouble.
3. Recover a save if loading fails. If the game reports a problem loading your saved game, it displays your save data and asks you to keep it; once the issue is fixed, you can import that data through the options screen to restore your game.

A practical example

Suppose you leave the game running with a modest swarm, close the tab, and come back two days later. On reopening, the popup might say you were away for about two days and list the larvae or meat your swarm generated in that period. If you instead return and see a storage error, the fix is the same as above: enable cookies/localStorage for the site and reload in Chrome or Firefox.

Quick reference

The key takeaway: offline progress in Swarm Simulator is reported to you on return, and it depends on the game being able to save and read your progress in browser storage.