Factorio 2.1: what enemy-expansion alerts actually tell you

As of 3 October 2026: Factorio’s 2.1 experimental changes include an alert for a newly built enemy base within active radar coverage. The useful distinction is coverage: having explored an area does not make it continuously watched. The alert reports a base being built, rather than promising advance warning of every attack.

Check the branch before changing a factory

The official stable download page currently labels its headless release 2.0.77; the experimental page labels 2.1.20 experimental. This article concerns the desktop 2.1 changes. It does not announce the same rollout for a console edition.

The latest entry on the official blog index checked today is dated 25 September. The 2.1.20 release notes, dated 22 September, include an artillery-reaction-group performance fix. They give no benchmark from which to promise a particular frame-rate improvement. The explanation below follows the developer’s documented behaviour; it is not a hands-on test.

What the expansion changes are trying to achieve

In Friday Facts #445, published on 7 August, Klonan describes generally larger, less frequent expansion groups. Group size takes account of evolution and map settings, while candidate placement was reworked toward open or previously cleared areas.

The same account records building cooldowns changed in 2.1.13 to 30 seconds by default and 10 seconds for Deathworld. Those numbers describe pauses between building entities. They are not a timetable telling you when the next attack will arrive.

What an alert does—and what silence cannot prove

The developer says an expansion-base alert appears when a worm or spawner is built in a chunk with active radar coverage. A distant radar scan might happen to catch the event, but that occasional scan is not continuous coverage.

For a returning player, the practical question is therefore narrower than “Can I see this place on the map?” Ask whether it was actively covered when the new structure appeared. An absent alert is not evidence that no expansion occurred anywhere.

A reversible way to investigate

Before switching, follow the developer’s experimental-release warning: keep backups of saves and blueprints. Converted 2.1 saves and blueprints cannot be downgraded to 2.0. The announcement also warns that mods may not be ready and that gameplay can still change.

If you choose to explore the changes, use a disposable copy and keep a short observation log:

1. Record the starting conditions. Note your game version, mods and relevant map settings. “It happened in 2.1” is less useful than a reproducible setup.
2. Choose one question. For an alert check, concentrate on the location of the newly built enemy structure and radar coverage there. Do not simultaneously turn the exercise into a damage or performance comparison.
3. Separate observation from explanation. Record an alert you actually saw. If you missed the construction event, mark the result inconclusive instead of declaring the feature broken.
4. Keep the original save intact. Compare notes before deciding whether this experimental branch suits the factory you care about.

This is a proposed observation method, not a report that we ran it. For a separate platform question, see the scope of Factorio’s ARM Linux support.

References

• FactorioBot. (2026, September 22). Version 2.1.20. Factorio Forums. https://forums.factorio.com/136265
• Klonan. (2026, June 26). Friday Facts #444 – 2.1 Experimental release. Factorio. https://www.factorio.com/blog/post/fff-444
• Klonan. (2026, August 7). Friday Facts #445 – The Biters Bite Back. Factorio. https://www.factorio.com/blog/post/fff-445
• Wube Software. (n.d.). Blog. Factorio. Retrieved October 3, 2026, from https://www.factorio.com/blog/
• Wube Software. (n.d.). Download: experimental branch. Factorio. Retrieved October 3, 2026, from https://factorio.com/download/experimental
• Wube Software. (n.d.). Download: stable branch. Factorio. Retrieved October 3, 2026, from https://factorio.com/download

Reading notes: All linked game records come from the developer’s own sites. The blog and download pages were checked on 3 October 2026; their current state can change. Release notes document intended changes and fixes, not independently measured results or popularity. No gameplay footage, game artwork or affiliate links are used.