--- title: "Valheim 1.0: what changes on disk, measured" description: "The new world format read file by file on a real machine, before release: the folder that replaces the .db/.fwl pair, the 42% the conversion costs, and the network version that decides who gets in." url: https://tickserv.com/guides/valheim-1-0-world-format site: "TickServ (https://tickserv.com)" lang: en published: 2026-09-06 games: [valheim] --- # Valheim 1.0: what actually changes on disk, measured Valheim 1.0 changes how the game writes worlds. Iron Gate says so in two sentences in its patch notes; we wanted to see the files. This page is the raw reading, with the method to redo it. Nothing here is lifted from a press release: it was all measured on **6 September 2026**, on a machine rented for the occasion, before the public release. ## The method, so you can reject it The new format has lived on Valheim's **public test branch** since May 2026 — so it is observable before 9 September. You reach it with the Steam code `yesimadebackups`, and the `lloesche/valheim-server` image gets there with `PUBLIC_TEST=true`. The reading was taken on a 2 shared-vCPU, 4 GB machine at Hetzner in Falkenstein. A world was generated on the stable branch (`0.221.12`), shut down cleanly so that it got written, and then the **same data directory** was restarted on the test branch. That switch is what shows the conversion. ## Before: two files On `0.221.12`, a saved world is a flat pair: ``` worlds_local/ tickserv.db 322,596 B tickserv.fwl 49 B tickserv.fwl.old 49 B tickserv_backup_auto-20260906114306.fwl 49 B ``` Two things we didn't expect, and they matter if you move a world by hand. The `.fwl` is **49 bytes** and exists from the moment the world is created: the `.db` only appears at the first save. So a folder holding just a `.fwl` isn't an empty world, it's a world that was never saved. And the game files its own copies **next to the world**, prefixed `_backup_auto-` — they are inside the folder you copy, with nothing to tell you. ## After: a folder, and pieces Restarted on `0.221.13`, the same world becomes this: ``` worlds_local/ tickserv/ _main.1.fwl2 49 B _main.1.db2 133,435 B _main.1.chunks 32 B _main.1.ok 4 B 00_00__0_1.chunk 1,464 B 00_01__0_1.chunk 6 B tickserv_backup_20260906-115918.db 322,596 B tickserv_backup_20260906-115918.fwl 49 B ``` The thing to take away: **the extension changes**. It is no longer `.fwl` but `.fwl2`, and the `.db` becomes `.db2` alongside `.chunk` files. A tool looking for `*.db` and `*.fwl` — a backup script, a host's importer — will find **nothing** on a 1.0 world. And it's silent: no error, just a missing world. The world's name lives in the **folder name**. The files inside are generic, and their number goes up with each save (`_main.1.*` then `_main.2.*`). ## The conversion keeps a full copy, and costs 42% The server log says `Moved old World save into backup!`. The original pair is kept as-is, renamed `_backup_`. Measured result: | | Bytes | | ----------------- | ------- | | Before conversion | 322,743 | | After conversion | 457,733 | That's **+42%**, not the doubling one might fear: the converted world (133 KB) is much smaller than the copy of the old one (322 KB) sitting next to it. That copy is also your only way out if the conversion goes wrong — the game cannot roll a world back on its own. ## What doesn't change: the download The dedicated server weighs the same as before. Read from SteamCMD's output on the test branch: **1,761,753,577 bytes**, about 1.76 GB. If you're resizing a machine for 1.0, the download is not what moved. ## Network version goes from 36 to 37 The server announces `Valheim version: l-0.221.13 (network version 37)`, against `network version 36` on `0.221.12`. That number is what decides whether a player gets in. Since Steam updates clients on its own, a server that hasn't switched yet becomes, at release, a server **nobody can enter** — until it updates. ## The game's backups don't switch off with the image's A hosting trap, this one. The `lloesche` image has a `BACKUPS` setting for its own hourly archives. It has **no effect** on the backups the game takes itself, and the server says so in its log: ``` Considering autobackup for World. […] short time: 7200, long time: 43200, backup count: 4 ``` Those are the three defaults Iron Gate documents (`-backups 4`, `-backupshort 7200`, `-backuplong 43200`): up to four copies, one at two hours then three at twelve-hour intervals. They live in `worlds_local`, so inside any archive you make of that folder. On a server that only runs for a few hours at a time, the three "long" ones never fire — so `-backups 1` loses almost nothing. ## Renaming a world works, in both formats Useful if you're moving house: Valheim loads a renamed world, it doesn't build a new one. Verified in both formats, and the judge is a log line — `Done generating locations` appears **only** for a new world. | Format | Action | `Done generating locations` | | ------- | ----------------------------- | --------------------------------- | | Pre-1.0 | `MyWorld.db` + `.fwl` renamed | 0 times (against 1 at generation) | | 1.0 | folder `MyWorld/` renamed | 0 times | In both cases the world's bytes were intact after renaming. ## What we did not measure The RAM and CPU of a 1.0 server **with players on it**: that needs real players, and we didn't want to publish an estimate dressed up as a measurement. Since the Deep North only appears on unexplored ground, the question won't really bite until a few exploration sessions in. The conversion's behaviour with mods wasn't tested either — Iron Gate explicitly writes that the new save system hasn't been. > These readings come from running Valheim servers ourselves. If you'd rather not deal with any of > it: [see Valheim](https://tickserv.com/games/valheim).