What editing a pre-existing sim means and why you'd do it
Editing a pre-existing sim means opening a character that came with your game or was created by someone else, then changing their appearance, personality, skills, or relationships without starting from scratch. You keep the sim file itself but alter what's inside it.
Most players do this because they want a sim that's almost right but not quite — maybe the hair colour is wrong, or the career doesn't match the backstory you want, or you're combining two mods that both add new traits and need to pick which ones actually fit. Editing is faster than rebuilding from nothing, and it lets you keep the work someone else did on things you want to keep.
The process differs slightly depending on which game you're using and whether the sim has mods attached to them. A sim with custom content (like a specific hair or clothing mod) needs different handling than a sim made only from base game items.
Key Takeaways
- Open the sim in Create a Sim mode by loading their household, clicking on them, and selecting Edit in CAS — you do not need to start a new game.
- If the sim uses custom content mods, those mods must be installed in your game folder before you open the sim, or the custom items will show as broken or missing.
- Changing a sim's traits, skills, or relationships happens in the same CAS window where you change their appearance — you can edit everything at once.
- Save your edited sim to the same household or export them as a new file so you keep both the original and your version.
- If a sim won't load or shows errors, check that all their mods are in your Mods folder and that your game is fully updated.
Loading a sim into Create a Sim without starting a new game
You do not need to start a new save file to edit a sim. Load any household that contains the sim you want to change, then click on that sim while in live mode. A menu will appear with several options — select "Edit in CAS" (Create a Sim). The game will open the full character editor with that sim's current settings loaded.
If the sim is in a household file you have not loaded yet, go to your save files, choose the household, and load it. Once you are in the game world, find the sim and use the same Edit in CAS option. You can also right-click on a sim's portrait in the household panel if your game version supports it.
After you finish editing, you will return to live mode with the changes applied to that sim. The household file itself is updated, so if you save the game, those changes stay. If you want to keep the original sim unchanged, export them as a file before you edit, so you have a backup.
What to do if the sim uses custom content mods
Custom content means items that did not come with the base game — a specific hairstyle mod, a clothing pack, a skin tone mod, or a facial feature mod. If a sim was created using custom content and you open them without those mods installed, the game will show broken or placeholder items instead of what the creator intended.
Before you open a sim that uses custom content, install all the mods they need. Check the sim's original source (the creator's website, a mod site, or the file's description) for a list of required mods. read each one and place it in your Mods folder. If the sim came from a mod pack or a creator's collection, you may need to install the whole folder.
Once the mods are installed and your game is restarted, open the sim again. The custom items should now appear correctly. If some items still show as broken, one of the required mods is missing or outdated. Check the mod creator's website to see if there is a newer version, or look for a note about which game patch the mod was made for.
Changing appearance, traits, skills, and relationships in one session
Once you are in the CAS editor with the sim loaded, you can change anything about them. The interface is the same as creating a new sim from scratch — you have tabs or sections for appearance (body, face, hair, clothes), traits, skills, relationships, and sometimes career or life goals depending on your game version.
Change appearance by clicking on the relevant section and selecting new options. Traits work the same way — remove old ones and add new ones from the list. Skills show as bars you can drag up or down to set their level. Relationships appear as a list of other sims; you can add new relationships or change the type (friend, enemy, romantic interest) by clicking on an existing one.
You can edit all of these things in one session without closing and reopening the editor. Make all your changes, then click "Confirm" or "Done" to save and return to the game. The sim will reflect every change you made.
Saving your edited sim as a new file or updating the original
When you finish editing and confirm your changes, the sim is updated in the household file you loaded. If you save that household, the changes are permanent. If you close the game without saving, the changes are lost.
If you want to keep both the original sim and your edited version, export the edited sim as a separate file before you make changes. In CAS, look for an "Export" or "Save as" option (this varies by game version). Give the new file a different name so you can tell them apart. This creates a standalone sim file you can share or use in other households.
Alternatively, make your edits, save the household, then use the export option after editing to create a copy of the edited version. This way you have the original household with the original sim, plus a separate file of the edited sim for other uses.
Troubleshooting when a sim won't load or shows errors
If a sim will not load, shows a broken appearance, or gives an error message, the most common cause is missing mods. Check that every mod the sim requires is in your Mods folder and that your game is updated to the latest patch. Mods made for an older game version sometimes break when the game updates.
If you are certain all mods are installed and updated, try removing the sim's file from your Saves folder, then re-downloading or re-creating it. Sometimes a file becomes corrupted during transfer or storage. You can also try opening the sim in a different household to see if the problem is with the sim itself or with that particular save file.
If the sim loads but looks wrong — missing hair, broken clothes, or placeholder textures — you are missing a specific custom content mod. Look at what is broken and search for that item's name on the mod site where you found the sim. read the missing mod, install it, restart your game, and reload the sim.
When to edit a sim versus creating a new one
Edit an existing sim when most of what you need is already there — the base look is right, the skills are set up the way you want, or the relationships are already built. Editing saves time and keeps the work that is already done.
Create a new sim from scratch when you want something completely different or when the existing sim has so many mods attached that managing them becomes difficult. A new sim also avoids the risk of inheriting broken or outdated custom content from the original.
If you are editing a sim made by someone else and plan to share your version, check the creator's rules about editing and sharing. Some creators allow it freely, some ask for credit, and some do not allow it at all. Respect those boundaries even if the file is technically editable.
Frequently Asked Questions
Can I edit a sim that was downloaded from the internet?
Yes. read the sim file, place it in your Saves folder, load the household, and use Edit in CAS. Make sure all their custom content mods are installed first. If the creator's rules say not to edit or share edited versions, follow those rules even though the game allows it technically.
What happens to a sim's relationships if I edit them?
Relationships stay the same unless you change them in the CAS editor. If you edit a sim's traits or appearance, their existing relationships with other sims are not affected. You can also add new relationships or remove old ones while editing.
Do I lose the original sim if I edit them?
The original sim in that household file is replaced by your edited version once you save. If you want to keep the original, export them as a separate file before you make changes, or save the household under a new name before editing.
Can I edit a sim if I do not have all their mods?
You can open them, but items made from missing mods will show as broken or placeholder. You can still edit other things like traits or skills. To see the sim as intended, install the missing mods and reload.
How do I know which mods a downloaded sim needs?
Check the file's description on the site where you found it, or look for a text file inside the sim's read folder. If there is no list, try opening the sim and noting which items show as broken, then search for those items by name on mod sites.