---
title: "Get the public signing key."
method: GET
path: "/api/signing-key"
tags: ["Signing"]
---

# Get the public signing key.

`GET /api/signing-key`

Returns the operator's ES256 (ECDSA P-256) public signing key in PEM, JWK, and fingerprint form. Use the public key to verify the `X-Philter-Signature` JWT header returned on successful `POST /api/filter` and `POST /api/explain` responses when output signing is enabled. This endpoint does not require authentication.

## Response `200`

Public signing key details.

- string

## Other responses

- `400` — Bad Request
- `401` — Unauthorized
- `413` — Content Too Large
- `415` — Unsupported Media Type
- `500` — Internal Server Error
- `503` — Service Unavailable

## Changes

- **2026-08-04** `ee79a60eea42` — 1 info
  - added the non-success response with the status `415`
- **2026-08-03** `e46672d44401` — 1 info
  - added the non-success response with the status `413`

[Change history](https://skmtc.dev/philterd/apis/philter-api/changes/api/signing-key/get.md)

---

[API](https://skmtc.dev/philterd/apis/philter-api.md) · [All operations](https://skmtc.dev/philterd/apis/philter-api/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/philterd/philter-api/revisions/d90a12a66fa6/schema)