Valheim’s stock dedicated server has no documented -seed startup option. To run a server with a specific seed, create the world in the Valheim client, stop the dedicated server, copy the complete world save (including its .db and .fwl data) into the server’s active save directory, and launch the server with -world set to that save’s exact name. If that world name already exists, Valheim loads the existing save instead of generating a new seed.
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What the server actually controls
Valheim separates world generation from server selection. The dedicated server’s documented -world argument tells it which save to open or create; it does not accept a seed value. Iron Gate’s guide describes the option this way: “-world “Dedicated” – A World with the name entered will be created. You may also choose an already existing World by entering its name.”
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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsThat distinction explains most failed seed attempts. Adding -seed MySeed to a normal server script does not configure the world. The reliable process is to generate the world in the client, migrate that save to the server, and then select it by name.
| Argument or setting | What it does | What it does not do |
|---|---|---|
-world |
Selects a world save by its exact save name, or creates a world with that name if none exists. | Does not reseed an existing save. |
-name |
Sets the server’s name as shown in the server browser. | Does not select the world save. |
-password |
Sets the password required to join. | Does not identify or generate a world. |
-savedir |
Changes the root directory in which Valheim stores saves. | Does not import a world by itself. |
-crossplay |
Uses Valheim’s PlayFab crossplay backend when supported by your setup. | Does not alter the world seed. |
Before you begin
Prepare both the client copy and the server before moving files. You need:
- A Valheim client in which you can create and save a new world.
- Access to the dedicated server’s save directory and launch script or hosting-panel settings.
- The exact world name you intend to use. Treat capitalization and spaces as significant when entering the name.
- A way to stop the server completely before replacing or adding save files.
- Backups of both the local source save and the server’s destination save before copying anything.
Do not perform the migration while the server is running. Valheim may still have the world open or be writing a save, so a live copy can leave the database and metadata out of sync.
Step 1: Create the seeded world in the Valheim client
Choose a new world
- Start Valheim and open the world-selection screen.
- Choose the control to create a new world.
- Enter a distinctive world name. This becomes the save basename that you will later put after
-world. - Enter the desired value in the world-creation Seed field. Valheim accepts the seed format offered by the client; record the value exactly if you need to reproduce it later.
- Create the world and enter it once so Valheim writes the initial save files.
- Exit to the menu and quit Valheim fully before copying the save.
The seed is stored as part of the world’s metadata when the client creates the save. You do not need to place the seed in the dedicated-server command line afterward.
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If you are testing multiple seeds, give each world a different name, such as MistyCoast-01 and MistyCoast-02. A name identifies a save; it is not merely a label displayed in the browser. Reusing a name that already exists on the server causes the server to load that existing world, so the new seed appears to have been ignored.
Step 2: Locate the save and back it up
Default save roots
Iron Gate documents these default Valheim save roots:
| Operating system | Default save root |
|---|---|
| Windows | %USERPROFILE%/AppData/LocalLow/IronGate/Valheim |
| Linux | ~/.config/unity3d/IronGate/Valheim |
The exact subdirectory layout can vary with the Valheim build and save mode. Look for the current world save directory and preserve the complete set of files for the world, not just a single file. The documented migration workflow uses matching .db and .fwl files; the .fwl metadata carries the seed in the implementation described by the migration documentation.
Make two separate backups
- Copy the newly created client world to a safe location outside the active Valheim save root. Include every file belonging to that world.
- Stop the dedicated server and copy its current save directory to a second backup location before changing it.
- Keep the backups until you have joined the migrated world and confirmed that the expected terrain and progress are present.
A backup is especially important if you plan to remove a same-named destination save. Deleting a save before verifying a replacement can turn a naming mistake into permanent world loss.
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Step 3: Stop the dedicated server and copy the complete world
Stop cleanly
Use the server application’s normal stop control or stop the service from the operating system. Wait for the process to exit rather than copying files immediately after issuing a stop command. The destination must not be writing the same world while you replace its files.
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Preserve the save pair and current layout
Copy the client world’s matching .db and .fwl files into the server’s active save location, or copy the complete current world directory when your installation uses directory-based saves. Keep the original basenames. Renaming only one half of the pair can make the server treat the world as missing or damaged.
When a server already has a world with the same name, do not overwrite it casually. The safer choices are:
- Use a new
-worldname for the imported world, leaving the existing save untouched. - Move the old destination save out of the active directory only after making and checking a backup.
- Replace the old save with the imported files only when you deliberately want the new world to take that name.
Step 4: Put the files under the server’s active save root
The files must be placed where the running server looks for saves. If you use Valheim’s default location, use the Windows or Linux root shown above. If your script includes -savedir, that argument overrides the default; copy the world under the directory selected by that option instead.
A common cause of “missing world” errors is copying files to the default path while the launch script points to a custom path. Treat -savedir as authoritative. Check the script, service definition, or hosting panel for the active value before transferring files.
Custom save roots
For example, a server launched with a custom root might contain an argument like:
-savedir "/srv/valheim-data"In that case, the imported world belongs under the save layout inside /srv/valheim-data, not under the account’s default ~/.config/unity3d/IronGate/Valheim directory. The quoted path is an example of syntax; use the path configured on your own server.
Step 5: Select the imported world with -world
Edit the dedicated-server launch script or panel field so -world exactly matches the imported save basename. For a world named MistyCoast-01, the relevant portion is:
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-world "MistyCoast-01"Keep the other arguments separate. A Windows-style command might look like:
valheim_server.exe -nographics -batchmode -name "Misty Coast Server" -port 2456 -world "MistyCoast-01" -password "use-a-long-password"A Linux service or shell script uses the same Valheim arguments, with the executable and surrounding service syntax appropriate to that installation:
./valheim_server.x86_64 -nographics -batchmode -name "Misty Coast Server" -port 2456 -world "MistyCoast-01" -password "use-a-long-password"These examples illustrate the world-selection argument; they are not a complete firewall, service, or update configuration. Do not add an invented -seed argument expecting it to change the imported world.
Keep the three names straight
-world: the save name Valheim opens.-name: the public server-browser name players see.-password: the join password.
Changing -name can make the server look different in the browser while leaving the selected world unchanged. Only -world, together with the files available in the active save root, determines which world is loaded.
Step 6: Start the server and verify the result
- Start the server with the edited script or panel configuration.
- Watch the console or service log during startup.
- Confirm that startup reaches “Game server connected.” Iron Gate uses this message as the indication that the server has connected successfully.
- Join from Valheim and inspect the terrain, spawn area, structures, and progression to confirm that this is the intended seeded world.
- Once verified, make a fresh backup of the working server save.
If the server connects but players see the wrong terrain, the connection itself is not proof that the correct save loaded. Check the world name, active save root, and destination files before changing gameplay settings.
Why a custom seed appears to be ignored
The script contains -seed
The stock dedicated server does not expose a documented seed startup flag. Remove the unsupported argument and use the client-created-world migration process. A command line can select a save with -world, but it cannot reseed an existing save.
The old world has the same name
Existing saves take precedence. If the server already contains MistyCoast-01 and you launch with -world "MistyCoast-01", Valheim opens that existing save rather than generating a new one from the seed you entered elsewhere. Choose a new world name or move the old save out of the active directory after a verified backup.
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Only one file was copied
The .db and .fwl files work as a set. Copying only the database or only the metadata can produce a missing, stale, or invalid world. Re-copy the complete world save while the server is stopped.
The files are in the wrong directory
If -savedir points somewhere else, the server will not use files placed in the default path. Compare the launch configuration with the location where you copied the save. This is also common when a managed host exposes a panel directory that differs from the operating system user’s default folder.
The world name does not match exactly
Check spaces, punctuation, capitalization, and the save basename. The value after -world must identify the imported save. Do not substitute the browser name from -name.
The server was not fully stopped
A running process can overwrite the copied files on its next save. Stop it, wait for the process to exit, restore the backup if necessary, and repeat the migration with the server offline.
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Iron Gate documents a default -saveinterval of 1,800 seconds (30 minutes). You can leave that default in place or set the option explicitly in the launch configuration:
-saveinterval 1800The interval controls how often the running server saves; it does not affect world generation or the seed. Iron Gate also documents automatic-backup arguments. Configure those according to your server’s available storage and retention needs, and still keep an offline or separate copy before migrations and destructive file changes.
The -crossplay option selects the PlayFab backend for crossplay-compatible operation. It likewise does not change the world seed or the save selected by -world. Decide on crossplay independently from the world-import procedure.
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Self-hosted server or managed hosting?
The seed workflow is the same in principle, but the operational work differs.
| Approach | Control | Operational effort | Main risk |
|---|---|---|---|
| Self-hosted Windows or Linux server | Direct control of files, -savedir, launch scripts, backups, and logs. |
You must locate paths, stop services, transfer files, and maintain scripts. | Copying to the wrong root or editing the wrong script can load another save. |
| Managed Valheim server hosting | The host panel may provide an upload area, world selector, and backup controls. | Less operating-system work, but you must follow the provider’s save-upload and restart process. | A panel’s displayed server name may not be the world basename; verify which field controls -world. |
For a managed service, upload the complete save set through the provider’s documented file manager or support workflow, set the world field to the exact basename, restart the instance, and inspect the console for a successful connection. Do not assume that changing a browser-name field imports or reseeds a world.
A repeatable migration checklist
- Create a new client world and enter the intended seed in the world-creation screen.
- Record the exact world name and seed value.
- Exit Valheim completely after the world has been created.
- Stop the dedicated server and back up its current save.
- Back up the client source save.
- Copy the complete world data, including matching
.dband.fwlfiles or the complete current directory layout. - Place the files under the active save root, taking
-savedirinto account. - Use a new destination name if a same-named save already exists, unless you intentionally replace it after a verified backup.
- Set
-worldto the exact imported save basename. - Leave
-nameand-passwordfor their own purposes. - Start the server and wait for “Game server connected.”
- Join and verify the expected world before deleting any backup.
Direct answers to common setup questions
Can I add a seed to the Valheim server start command?
Not with the stock dedicated server’s documented arguments. Create the seeded world in the client, migrate its complete save, and select it with -world.
Does changing -world generate a world from a new seed?
It creates a world only when that name has no existing save. If the name already exists, Valheim loads that save and does not reseed it.
Where should the files go on Linux or Windows?
Use the documented default root for your operating system unless the launch configuration includes -savedir. A custom -savedir takes precedence over the default location.
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What proves the migration worked?
The server log should reach “Game server connected,” and a client joining should see the intended terrain and world progress. Check the selected name and save path if the connection succeeds but the world is wrong.
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