Elden Ring Compass — Save file / Progression Website

Check it out here: www.eldenringcompass.com

Upload (or continuously poll) your Elden Ring save and the site reads your progression — inventory, bosses defeated, graces, map markers, and more — entirely in your browser. Nothing is ever written back to the save.

Key Technologies

• TanStack Start (full-stack React framework) + TanStack Router (file-based routing)
• React 19 (with the React Compiler)
• Effect + @effect/atom-react — app state and the in-memory data layer (no TanStack Query, no IndexedDB)
• shadcn (Base UI variant, @base-ui/react) + Tailwind CSS v4
• Leaflet / react-leaflet — tiled interactive map
• TanStack Table + TanStack Virtual — virtualized data tables
• Bun + Turborepo — package manager and monorepo task runner
• Vite / Nitro — bundling and the production server
• oxlint / oxfmt — linting and formatting
• tsgo (TypeScript native preview) — type checking
• Vitest + Playwright — unit, browser, and E2E tests

Monorepo Layout

Package	What it is
apps/web	The website itself.
packages/data	The single runtime data source — game data + item icons baked by the extractor. This is all the web app consumes.
packages/save-parser (save-parser-ts)	Pure-TypeScript Elden Ring save parser. Runs in the browser/worker.
packages/extractor (er-extractor)	Build-time CLI that reads an installed copy of the game and bakes everything data needs (names, stats, markers, icons, graces, event scripts).
packages/vendored-data	Build-time-only reverse-engineered constants the extractor can't derive from the install (event-flag tables, AES/RSA keys, param schemas). See its README for provenance.
packages/config/*	Shared TypeScript / oxlint config.

Data & Save Parsing

The save parser is pure TypeScript — the old Rust/WASM save-editor stack has been removed (the TS port is dramatically faster and ships with no native deps).

Game data is produced by our own er-extractor, which reads the installed game directly (Oodle decompression via bun:ffi, dvdbnd unpacking, FMG/PARAM/MSB/EMEVD parsing) and bakes the result into @elden-ring-compass/data. This replaces the external erdb dataset the project originally relied on. The reverse-engineered constants that can't be read from the install are vendored in packages/vendored-data, adapted from these excellent upstream projects:

• ER-Save-Lib — save-format constants (event-flag table, regulation key)
• UXM-Selective-Unpack — archive RSA keys + file-path dictionary
• soulsmods / Paramdex — PARAMDEF field schemas for regulation.bin
• soulstruct — EMEVD instruction dictionary (EMEDF)

Features

• In-browser save parsing: your save is parsed locally — it never leaves your machine, and the site never writes to it.
• Continuous save polling: point the tab at your save and it keeps the view updated as you play, without re-uploading.
• Local storage sync: map position, row selection, and column filters all persist locally.
• Tiled interactive map with item/boss/grace markers.

Additional Details

The default code snippet requires Node.js for the HTTP server, but any simple HTTP file server will work.

If you prefer, you can manually upload the save without using continuous polling.

Can this get me banned?

No, this site has no ability to make changes to the save. For edits to be possible, you would either need to redownload your save after uploading or the HTTP server would need to support PUT/POST requests, which if you use the snippet provided it doesn't. (Not that my site even makes these requests) Elden Ring is fine with other programs reading or copying the save. Steam does this repeatedly to make cloud backups.

Let me know what you think!

Contributing

Prerequisites

The web app only needs Bun. A reproducible toolchain is also provided via Nix (flake.nix).

Note: building game data from scratch with er-extractor additionally requires an installed copy of Elden Ring and the Rust toolchain (for the extractor's native image codec). You do not need either to run or develop the web app — the prebuilt data package is committed.

Setting up Nix (recommended)

If you have Nix installed with flake support enabled:

# Enter the development shell (auto-activates with direnv if installed)
nix develop

# Or if using direnv:
direnv allow

Without Nix

Just install Bun.

Setup

Install dependencies:

bun install

Development

Start the development server:

bun run dev

Checks

# Lint + format
bun run lint

# Type checking (tsgo)
bun run typecheck

# Tests
bun run test

# Full production build
bun run build