Cities: Skylines 1 Won't Launch: Separate Mods, Logs and Memory Clues

Run the reversible launch test first

Paradox's November 2026 article uses Steam launch options to disable Workshop and mods. That is a diagnostic comparison, not a universal cure. Keep the game's normal files and saves intact for the first test.

1. Record whether the game closes before the menu, crashes after the menu or fails only when opening one city.
2. On Steam, temporarily add Paradox's documented `-noWorkshop -disableMods` launch options for the original game.
3. Launch once and record the result, including whether the menu appears and whether the same crash occurs.
4. If the game starts, re-enable content in small batches rather than restoring everything at once.
5. If it still crashes, continue to the log rather than immediately deleting user data.

References: Paradox Support: Cities won't launch or crashes after launch

Read the log as evidence, not as a diagnosis

Paradox names `output_log.txt` in the game installation's `Cities_Data` folder and describes examples involving Citrix Workspace and very low free physical/paging memory. Those examples are clues in the article, not proof that every machine with those programs is affected. Preserve the top of the log and the crash time for support.

1. Open the log after a failed launch and note the first repeated error or the earliest relevant lines near startup.
2. If the log explicitly names a third-party component, record its exact name and version; do not uninstall software solely because another player's post blamed it.
3. If the log reports memory pressure, close other applications and review system memory/paging settings using platform support; do not assume a fixed page-file size is safe for every PC.
4. Keep the full log private unless you have reviewed it for usernames or paths; send it through the official support route.

References: Paradox Support: Cities won't launch or crashes after launch

Choose a branch by what still works

References: Paradox Support: Cities won't launch or crashes after launch · Paradox Support: Save does not load / mods cause errors

Before you play

• I noted whether the menu, a new city and the affected city each load.
• I made one no-mod launch comparison.
• I recorded the game version and copied relevant log lines.
• I did not delete saves or remove software based only on a forum anecdote.
• I confirmed the instructions are for the 2015 game.

Frequently asked questions

Sources & revision notes

Editorial revision: November 6, 2026; not a gameplay test date. The reference notes identify source limits and version differences.

1. Paradox Support: Cities won't launch or crashes after launch (Official)

   Legacy Cities: Skylines (2015) PC troubleshooting, updated November 3, 2026. It describes mod/Workshop isolation and collecting output_log.txt; follow current support instructions and preserve saves.

2. Paradox Support: Save does not load / mods cause errors (Official)

   Paradox's Cities: Skylines (2015) support article, updated May 17, 2026. It recommends testing Steam launch options --disableMods --noWorkshop before removing mods and says to back up Addons. Not applicable to Cities: Skylines II.

3. Cities: Skylines player discussions (Community)

   External Steam topics are user-generated and may refer to old mods, builds or DLC. They are leads, not verified fixes; never upload a private city save publicly.