# REST API reference

nxdns serves its admin API itself, on `web.bind:web.port` (default port 8080), as plain HTTP. TLS termination, where an operator wants it, belongs to a reverse proxy in front; the session cookie deliberately omits the `Secure` attribute so the supported plain-HTTP LAN deployment works.

The machine-readable contract is `src/web/openapi.yaml`, which the running server hands out unauthenticated at `GET /api/openapi.yaml`. Request and response schemas for every operation live there. When this page and the YAML disagree, the YAML wins.

The route table is `src/web/routes.zig`; the [Operations](#operations) table below carries all 64 of its entries.

## Conventions

- All request and response bodies are JSON (`application/json`), except `/metrics` (Prometheus text format), `/api/openapi.yaml` (YAML) and `/api/queries/live` (`text/event-stream`).
- Field names are snake_case, matching settings keys and SQL column names.
- Every error response carries the envelope `{"error": "<message>"}`. The message is operator-facing text; internal detail never reaches the wire — a 500 body is generic and the cause goes to the server log.
- Request bodies are strict: an unknown field is a 400, a body over 1 MiB is a
  413.
- A request whose path matches but whose method does not answers 405 with an `Allow` header. An unknown `/api` path is a JSON 404; unknown non-`/api` paths fall through to the embedded SPA (`index.html`), so client-side routing works.
- Item routes (`{id}`) match a positive integer id only.
- Mutations take effect live, upstreams and `/api/settings` included: a write rebuilds or reconfigures the owner it belongs to in-process. The exceptions are the settings keys that create or destroy a socket — the DNS, web, DoH and DoT bind addresses, ports and enabled flags. Writing one of those commits the row and reports `restart_pending: true` on `GET /api/config/status`; the settings envelope lists exactly those keys under `restart_required`.
- Every route has a policy class — `read`, `config_write` or `runtime_action` — and in file mode the `config_write` routes are refused. See [Configuration authority](#configuration-authority).

## Authentication

Cookie sessions, in memory, no accounts — one operator password. Setting that password is [set up admin authentication](../how-to/set-up-admin-authentication.md).

- Authentication is on exactly when `web.password_hash` is set. When no password is set, every route is open and `POST /api/auth/login` answers `{"authenticated": true, "auth_required": false}` without setting a cookie.
- `POST /api/auth/login` takes `{"password": "..."}`. A correct password answers 200 with a `Set-Cookie` for `nxdns_session` (`HttpOnly; SameSite=Lax; Path=/`, `Max-Age` = the session TTL). A wrong password is a 401; a stored hash the server cannot read is a 500, never a 401. Login attempts spend rate-limit tokens like any other request, and argon2id verification is deliberately slow.
- Every route whose auth policy is `session` answers 401 `{"error": "authentication required"}` without a valid cookie.
- Sessions live `web.session_ttl_hours` (default 24) from login; use does not extend the lifetime. The table holds 32 sessions; a 33rd login evicts the least recently used. Nothing is persisted — a server restart logs every operator out.
- Changing the password through `PUT /api/settings` revokes every live session immediately; the new password applies without a restart.
- `POST /api/auth/logout` ends the cookie's session and clears the cookie. The route is `.session` like any other, so with a password configured the router answers 401 before the handler runs when the cookie is missing, expired, revoked or already logged out; only a live session gets the 200. With no password configured every session route is open and logout answers 200.

## Rate limiting

A token bucket per client address: capacity and refill are both `web.api_rate_limit_per_min` (default 300) per minute, so a page-load burst up to the capacity is admitted and the long-run rate holds.

- An over-budget request answers 429 `{"error": "rate limited"}` with a `Retry-After` header giving the seconds until a token is available (rounded up, never zero).
- Loopback addresses (127.0.0.0/8 and ::1) are exempt while `web.api_localhost_exempt` is true (the default).
- The address a bucket keys on is the socket peer, unless that peer is listed in `web.trusted_proxies`. For a listed peer the address is instead the **last** entry of the request's `X-Forwarded-For` — the entry the proxy appended, which is the only one a client cannot write. A request from a trusted proxy with no such header keys on the proxy itself; one whose last entry is not an IP literal is answered 400, because the alternative is granting the proxy's own loopback exemption to whoever sent it. Only `X-Forwarded-For` is read; `Forwarded` (RFC 7239) and the PROXY protocol are not.
- Without `web.trusted_proxies`, a same-box reverse proxy makes every request loopback, so the default exemption disables the limiter for all remote clients. Set the proxy's address there, or set `web.api_localhost_exempt = false`.
- Exempt routes, which never consult a bucket: `/metrics` and `/api/health` (a Prometheus scrape must never see 429) and `/api/queries/live` (one long-lived stream must not drain its address's bucket; it is bounded by the SSE connection cap instead).
- The limiter tracks at most 4096 addresses. When the table is full and no slot is reclaimable, requests from unknown addresses are refused with 429.

## Live query stream (SSE)

`GET /api/queries/live` is server-sent events over chunked transfer, `Content-Type: text/event-stream`, `Cache-Control: no-store`.

- The stream opens with `retry: 3000`, so a browser `EventSource` reconnects on its own after a drop.
- Each query is one frame: `event: query` and a single `data:` line of JSON. The payload is the `Provenance` object — the body of `GET /api/queries/{id}` without its `id`, which does not exist yet because a live entry precedes its own insert. Its six groups are `request`, `group`, `policy`, `rewrites`, `route` and `response`.
- A `: ping` comment heartbeat goes out after 15 s of quiet, keeping middleboxes from reaping the idle connection.
- Each subscriber buffers up to 64 entries. A client too slow for the query rate overflows its buffer and the server ends the stream cleanly after delivering what the buffer held — queries are never held back for a slow reader. There is no gap marker: on reconnect, re-sync through `GET /api/queries`, which has the missed rows.
- Connections per client address are capped at `web.sse_max_connections_per_ip` (default 3); over the cap is a 429. The cap binds loopback too. The server holds at most 32 concurrent streams in total; when all slots are taken, the answer is a 503.

## Configuration authority

Which authority is live decides whether the API may write configuration. Under `nxdns run` the database is authority and every route behaves as it always has. Under `nxdns run --config FILE` the file is authority, and the routes that would edit configuration are refused: the file is the only place configuration changes, and a restart is what applies them.

### The refusal

A `config write` route in file mode answers **403** with the ordinary error envelope:

```json
{"error":"configuration is managed by /etc/nxdns/config.zon; edit the file and restart"}
```

There is no `code` field and no richer body. 403 is used for nothing else in this API, so the status alone is the machine-readable part, and a client that wants to know the mode in advance reads it from `GET /api/config/status` rather than probing for errors.

**401 comes first.** The router matches the path, spends a rate-limit token, checks the session, and only then checks the policy. So an unauthenticated request to a `config write` route in file mode is a 401, not a 403 — answering 403 first would tell an anonymous caller which routes exist.

`runtime action` and `read` routes are unaffected in both modes. Pausing blocking, refreshing blocklists, reloading certificates and logging in are operations on a running process, not statements about configuration, so a file-mode box still does all of them.

`DELETE /api/clients/{id}` is the one route whose answer depends on the row. Deleting a client the file does not declare is a runtime action and succeeds: without it, a mis-identified or departed device would be immortal in file mode, since the file can add addresses but never remove one it has never named. Deleting a client the file *does* declare contradicts the file, and answers the same 403.

### Discovering the authority

`GET /api/config/status` answers with the authority and the process's restart state:

| Field | Meaning |
| --- | --- |
| `authority` | `"database"` or `"managed_file"`. |
| `path` | The managed file's path, or `null` in database mode. |
| `reconciled_at` | Unix seconds when this process loaded the file, or `null` in database mode. |
| `restart_pending` | True once this process has committed a configuration change that only a restart applies. |

All four keys are always present; the two nullable ones carry `null` rather than being omitted, so a client can read `authority` without probing.

```json
{"authority": "database", "path": null, "reconciled_at": null, "restart_pending": false}
{"authority": "managed_file", "path": "/etc/nxdns/config.zon", "reconciled_at": 1786474016, "restart_pending": false}
```

The route requires a session, which is why the filesystem path is here rather than on the open `/api/version` and `/api/health`.

`restart_pending` is per-process state and nothing but process exit clears it. It rises for exactly one kind of change: a settings key that creates or destroys a socket — the DNS, web, DoH and DoT bind addresses, ports and enabled flags. Every other write, upstreams included, is applied in-process and leaves the flag alone. It is never persisted, so a `false` read after a restart means the restart happened, not that the flag was cleared. In file mode it stays false: those writes are refused before any handler runs.

`reconciled_at` answers exactly one question: **when did this process last read the file?** Compare it against the file's mtime to spot a restart that has not happened yet. It is a hint and not a verdict, in both directions — a clock that stepped, or a copy that preserved mtimes (`git checkout`, `rsync -a`), can make a newer file look older, and the database can change without either timestamp moving. It does not tell you whether the file and the running configuration agree; answering that would take content hashing, which nxdns deliberately does not do.

## Operations

Auth `open` means no session is required; `session` means a valid session cookie is required whenever a password is set. Rate limit `counted` spends a token; `exempt` never consults the limiter. Policy `config write` is the class refused in file mode; `read` and `runtime action` are always served.

| Method | Path | Auth | Rate limit | Policy | Purpose |
|---|---|---|---|---|---|
| GET | `/metrics` | open | exempt | read | Prometheus metrics |
| GET | `/api/health` | open | exempt | read | Health rollup |
| GET | `/api/version` | open | counted | read | Build and uptime |
| GET | `/api/openapi.yaml` | open | counted | read | This API's OpenAPI document |
| POST | `/api/auth/login` | open | counted | runtime action | Log in |
| POST | `/api/auth/logout` | session | counted | runtime action | Log out |
| GET | `/api/queries` | session | counted | read | Query log rows for the Activity page |
| GET | `/api/queries/{id}` | session | counted | read | One query, fully explained |
| GET | `/api/queries/live` | session | exempt | read | Live query stream (server-sent events) |
| GET | `/api/overview` | session | counted | read | Everything the Overview page draws, for one period |
| GET | `/api/lookup` | session | counted | read | Explain a domain |
| GET | `/api/diagnostics` | session | counted | read | Operational event log |
| DELETE | `/api/diagnostics` | session | counted | runtime action | Purge every resolved event |
| GET | `/api/diagnostics/{id}` | session | counted | read | One operational event |
| DELETE | `/api/diagnostics/{id}` | session | counted | runtime action | Purge one resolved event |
| GET | `/api/groups` | session | counted | read | List groups |
| POST | `/api/groups` | session | counted | config write | Create a group |
| GET | `/api/groups/{id}` | session | counted | read | Read a group |
| PUT | `/api/groups/{id}` | session | counted | config write | Update a group |
| DELETE | `/api/groups/{id}` | session | counted | config write | Delete a group |
| GET | `/api/groups/{id}/sources` | session | counted | read | Blocklist sources assigned to a group |
| PUT | `/api/groups/{id}/sources` | session | counted | config write | Replace the assignment |
| GET | `/api/blocklists` | session | counted | read | List blocklist sources |
| POST | `/api/blocklists` | session | counted | config write | Add a blocklist source |
| POST | `/api/blocklists/update` | session | counted | runtime action | Refresh every enabled source now |
| GET | `/api/blocklists/{id}` | session | counted | read | Read a blocklist source |
| PUT | `/api/blocklists/{id}` | session | counted | config write | Update a blocklist source |
| DELETE | `/api/blocklists/{id}` | session | counted | config write | Delete a blocklist source |
| GET | `/api/rules` | session | counted | read | List rules |
| POST | `/api/rules` | session | counted | config write | Create a rule |
| GET | `/api/rules/{id}` | session | counted | read | Read a rule |
| PUT | `/api/rules/{id}` | session | counted | config write | Update a rule |
| DELETE | `/api/rules/{id}` | session | counted | config write | Delete a rule |
| GET | `/api/local-records` | session | counted | read | List local DNS records |
| POST | `/api/local-records` | session | counted | config write | Create a local record |
| GET | `/api/local-records/{id}` | session | counted | read | Read a local record |
| PUT | `/api/local-records/{id}` | session | counted | config write | Update a local record |
| DELETE | `/api/local-records/{id}` | session | counted | config write | Delete a local record |
| GET | `/api/forward-zones` | session | counted | read | List forward zones |
| POST | `/api/forward-zones` | session | counted | config write | Create a forward zone |
| GET | `/api/forward-zones/{id}` | session | counted | read | Read a forward zone |
| PUT | `/api/forward-zones/{id}` | session | counted | config write | Update a forward zone |
| DELETE | `/api/forward-zones/{id}` | session | counted | config write | Delete a forward zone |
| GET | `/api/clients` | session | counted | read | List clients |
| GET | `/api/clients/{id}` | session | counted | read | Read a client |
| PUT | `/api/clients/{id}` | session | counted | config write | Rename or regroup a client |
| DELETE | `/api/clients/{id}` | session | counted | runtime action | Forget a client |
| GET | `/api/client-prefixes` | session | counted | read | List client prefixes |
| PUT | `/api/client-prefixes` | session | counted | config write | Replace the prefix table |
| GET | `/api/upstreams` | session | counted | read | List upstream resolvers |
| POST | `/api/upstreams` | session | counted | config write | Add an upstream |
| GET | `/api/upstreams/{id}` | session | counted | read | Read an upstream |
| PUT | `/api/upstreams/{id}` | session | counted | config write | Update an upstream |
| DELETE | `/api/upstreams/{id}` | session | counted | config write | Delete an upstream |
| GET | `/api/pause` | session | counted | read | Read the pause state |
| POST | `/api/pause` | session | counted | runtime action | Pause or resume blocking |
| GET | `/api/settings` | session | counted | read | Read the scalar settings |
| PUT | `/api/settings` | session | counted | config write | Update settings |
| GET | `/api/config/status` | session | counted | read | Read the configuration authority and restart state |
| POST | `/api/certs/reload` | session | counted | runtime action | Reload the TLS certificates from disk |

There is no `POST /api/clients`: client rows come from DNS activity or import, never from the API.

The two diagnostics deletes purge history only. `DELETE /api/diagnostics/{id}` answers 204 for a resolved event, 409 for one that is still active — an open episode is the current state of the box, not history — and 404 for an id no row holds. `DELETE /api/diagnostics` removes every resolved event and answers `{"purged": N}`, leaving the active ones. Events still resolve on their own; these only decide when the resolved rows go.

Static assets are not routes. The router sends unmatched non-`/api` paths to the embedded SPA before any auth or rate-limit check.

## Settings keys

The envelope both operations answer with is `{settings, restart_required}`: the stored values, and the list of keys a restart applies — the bind addresses, ports and enabled flags of the four listeners, and nothing else. Every other key is applied by the PUT that changes it. It says nothing about the live authority or a restart already owed — those are per-process facts, and `GET /api/config/status` is their one home.

`GET /api/settings` and `PUT /api/settings` speak the `section.field` keys of [the configuration reference](configuration.md), with the values in their database spelling — notably `logging.level` is `"error"`, not `"err"`. Two keys behave differently over the API than in the file: `web.password` is write-only (accepted on a `PUT`, never returned, hashed before storage), and `web.password_hash` is neither readable nor directly writable, because a client that could install a hash could install one whose password it already knows.

In file mode `PUT /api/settings` is refused with the 403 above, password changes included. The password then lives where the rest of the configuration lives: set `web.password` in the file and restart. See [Password and hash](configuration.md#password-and-hash).

## Schemas

Request and response schemas for every operation live in the OpenAPI document: `src/web/openapi.yaml` in the repository, or `GET /api/openapi.yaml` from a running server.

### Policy reasons

Two places carry the same closed set of tags: `policy_reason` on a `GET /api/queries` row and on a `GET /api/queries/{id}` body (where it is `policy.reason`, and where the live stream sends the same field), and `reason` on a `GET /api/lookup` answer. The tag names what decided the query.

The first nine are the matcher's own verdicts, listed in the order they are consulted — the first that matches wins, so a rule always outranks a list.

| Tag | Decided by |
| --- | --- |
| `rule_allow_exact` | An `exact` rule with action `allow` |
| `rule_block_exact` | An `exact` rule with action `block` |
| `rule_allow_wildcard` | A `wildcard` rule with action `allow` |
| `rule_block_wildcard` | A `wildcard` rule with action `block` |
| `rule_allow_regex` | A `regex` rule with action `allow` |
| `rule_block_regex` | A `regex` rule with action `block` |
| `blocklist_exception` | An `@@` exception line in a downloaded list |
| `blocklist_domain` | A plain name in a downloaded list |
| `blocklist_wildcard` | A domain anchor (`||name^`) in a downloaded list |

The rest name a pipeline step that answered the query without consulting the matcher, and appear on a query row only.

| Tag | Decided by |
| --- | --- |
| `local_record` | A configured local record, answered before filtering |
| `forward_zone` | A configured forward zone, answered before filtering |
| `non_in_class` | The question was not class IN, so no rule could apply |
| `paused` | Filtering was paused |
| `snapshot_unavailable` | No filter snapshot was published yet, so the query went unfiltered |
| `no_match` | The matcher evaluated the name and nothing matched |
| `protocol_error` | A parsed request refused on protocol grounds — BADVERS, NOTIMP, a malformed EDNS OPT |

`policy_action` says which way the verdict went: `block`, `allow`, or `not_evaluated` for a query answered before any policy could apply. `/api/lookup` answers `none` when nothing matched, where a query row says `no_match`.

`route_kind` says where the answer came from: `blocked`, `local`, `forward_zone`, `upstream`, `cache` or `rejected`.

A non-empty `rewrites.cname_target` on a query detail means the decision landed on a CNAME target rather than on the name the client asked for; `policy.reason` is then the target's own reason. `/api/lookup` does not follow CNAMEs.

### Coverage

Every window-bounded read — `GET /api/queries` and `GET /api/overview` — answers with a `coverage` object: `available_since` is the oldest instant the query log is still complete for, and `complete` is true only when the window the request asked about starts at or after it. Retention deletes rows and advances the watermark in one transaction, so a client can tell an empty window from a pruned one instead of charting the gap as zero. A request with no lower bound at all asks about the whole of history, and is never complete.

Each of these responses reads its rows and its watermark inside one SQLite read transaction, so retention cannot prune between the two and hand back pre-prune rows tagged with a post-prune `available_since`. `GET /api/overview` puts every Overview panel inside that one transaction, so its totals and its four breakdowns describe one database state. Coherence stops there: two separate requests are two separate reads, and queries logged between them can move the counts.
