hidane (火種, the seed of fire) — a Firestore emulator without Java.

hidane (pronounced hi-da-ne) aims to be a drop-in replacement for the official Cloud Firestore emulator: a single Rust binary that speaks the same gRPC, REST and WebChannel wire protocols, evaluates the same Security Rules, reads and writes the same import / export directories, and runs under firebase-tools. No JDK to install. Starts in milliseconds. Tested for parity against the official emulator as the oracle.

v0.2.0 enforces Security Rules. hidane serves the Firestore API over gRPC, REST and WebChannel: documents, queries, aggregations, vector search, transactions, listeners, exports and imports, and the emulator's own endpoints, each checked against the official emulator; firebase-tools launches it in place of the official one. Since v0.2.0 it evaluates firestore.rules as the official emulator does, with its denial messages, :ruleCoverage and debug() output (v0.1 allowed every request). The plan is in docs/ROADMAP.md, the work in issues.

curl -fsSL https://hidane.dev/install.sh | sh             # or Homebrew, npm, cargo: see Install
hidane exec -- firebase emulators:start --only firestore  # under firebase-tools, no Java needed
hidane --host 127.0.0.1 --port 8080                       # or on its own:
export FIRESTORE_EMULATOR_HOST=127.0.0.1:8080

hidane exec runs the command with hidane standing in for java and the official jar, for that command only (ADR 0006).

The official emulator is a closed-source Java application shipped as a jar. Three things about it hurt everyday local development and CI (details and raw logs: docs/why.md):

All numbers are measurements, but not side by side: the official emulator's were taken in Phase 0 on a loaded workstation (see the caveat in docs/why.md), hidane's later on a quiet one (results/startup-memory-hidane.txt, results/listen-batch-writes-hidane.csv). A same-machine comparison is #50.

Which clients can use hidane depends on the transport their SDK speaks to an emulator (docs/compatibility.md). "Verified" means the client's results were compared with the official emulator's (results/):

hidane treats the official emulator as the oracle. Scripts in tools/oracle/ ask the official emulator how it answers — 31 recorded fixtures so far, from value ordering to WebChannel framing, export files and Security Rules — and the test suite replays every recording against hidane; SDK transcripts from both emulators are compared in results/. A parity table with a badge will follow (#43). No claim of compatibility without a test behind it. Differences that are intentional (performance bugs and known defects of the official emulator that hidane will not reproduce) are listed in docs/parity-exceptions.md.

Two open-source emulators came closest in our survey. Both document a gRPC endpoint for the server SDKs; neither documents REST, WebChannel, Security Rules or running under firebase-tools, which is the gap hidane is built to close.

As read from their READMEs in October 2026; corrections welcome.

Every channel installs the same release binaries: macOS (arm64, x86_64), Linux (arm64, x86_64; static, any distribution) and Windows (x64).

curl -fsSL https://hidane.dev/install.sh | sh   # macOS, Linux: into ~/.local/bin, SHA-256 checked
brew install hidane-dev/tap/hidane               # Homebrew (macOS, Linux)
npm install --save-dev hidane                    # npm, every platform: the binary is an optional dependency
cargo binstall hidane                            # the release archive, through cargo-binstall
cargo install hidane                             # from source, Rust 1.88 or newer
dart pub global activate hidane                  # pub.dev: a launcher that downloads the binary on first run
docker run --rm -p 8080:8080 ghcr.io/hidane-dev/hidane

Then export FIRESTORE_EMULATOR_HOST=127.0.0.1:8080, or let firebase emulators:start launch it through hidane exec. The archives, their checksums and build provenance are on GitHub Releases (how to verify them). The macOS binaries are not signed yet: one downloaded with a browser needs xattr -d com.apple.quarantine hidane.

• Why hidane — the measurements behind the table above, with sources
• Compatibility — transport per SDK, how each finds the emulator, which RPCs they use
• Parity exceptions — where hidane and the official emulator intentionally differ
• Roadmap — scope of v0.1 / v0.2 / v0.3, targets, risks
• Decision records — storage engine, gRPC stack, WebChannel timing, Rules engine, license (all drafts)
• Benchmark results — the official emulator baseline, hidane's measurements and the SDK differentials
• Releasing — release assets, checksums, provenance and how a release is cut

hidane is built issue by issue, each one measured against the official emulator first. Please open an issue before sending a pull request; the code you would touch may be about to change shape. Parity-gap reports (a request whose answer differs from the official emulator's) are especially welcome. See CONTRIBUTING.md, the issue templates and Discussions. Security issues go through private vulnerability reporting.

• Local development and CI only. hidane is not a production database and must not be exposed on a network without authentication.
• Security Rules are evaluated once per condition: where the official emulator evaluates twice and lists the reasons of both passes in a denial (firebase-tools#6252), hidane lists one.
• Cloud Firestore only. The Realtime Database, Cloud Storage and Auth emulators are out of scope.
• Features the official emulator does not implement either (the Admin API, TTL, point-in-time recovery, bundles) stay unimplemented. See docs/parity-exceptions.md.

hidane is a clean-room implementation written from the public protobuf definitions (googleapis), the public Firebase and Google Cloud documentation, and black-box observation of the official emulator. No code was decompiled or ported from the official jar. Thanks to the authors of skunkteam/rust-firestore-emulator and YutaUra/firestore-emulator, whose public work helped us map the landscape, and to the model projects whose approach to parity testing we follow: dynoxide and zerobrew.

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option (ADR 0001).

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Firebase, Cloud Firestore and Google Cloud are trademarks of Google LLC. hidane is an independent open-source project and is not affiliated with, endorsed by, or sponsored by Google.