diff --git a/BUILD.bazel b/BUILD.bazel
index a090b69..f7e7481 100644
--- a/BUILD.bazel
+++ b/BUILD.bazel
@@ -57,7 +57,7 @@ npm_package(
         ":tinyland_security",
     ],
     package = "@tummycrypt/tinyland-security",
-    version = "0.2.3",
+    version = "0.3.0",
     visibility = ["//visibility:public"],
 )
 
diff --git a/MODULE.bazel b/MODULE.bazel
index 1981645..be67073 100644
--- a/MODULE.bazel
+++ b/MODULE.bazel
@@ -1,6 +1,6 @@
 module(
     name = "tummycrypt_tinyland_security",
-    version = "0.2.3",
+    version = "0.3.0",
     compatibility_level = 1,
 )
 
diff --git a/package.json b/package.json
index 2f89a8f..966930a 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@tummycrypt/tinyland-security",
-  "version": "0.2.3",
+  "version": "0.3.0",
   "description": "IP hashing, encryption, risk scoring, device detection, VPN detection, rate limiting, and timing-safe utilities",
   "type": "module",
   "main": "./dist/index.js",
diff --git a/src/index.ts b/src/index.ts
index 490db36..4ee0758 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -122,3 +122,13 @@ export {
 	deactivateIpBan, getActiveBans, cleanupExpiredBans,
 	configureIpBanStore
 } from './ipBans.js';
+
+
+export {
+	applyDefaultSecurityHeaders,
+	getDefaultSecurityHeaders,
+} from './securityHeaders.js';
+export type {
+	SecurityHeaderPreset,
+	SecurityHeadersOptions,
+} from './securityHeaders.js';
diff --git a/src/securityHeaders.ts b/src/securityHeaders.ts
new file mode 100644
index 0000000..a95eb77
--- /dev/null
+++ b/src/securityHeaders.ts
@@ -0,0 +1,101 @@
+/**
+ * Security headers for HTTP responses.
+ *
+ * Provides convenience functions for applying a known-safe set of security
+ * headers to a Headers object, with three presets reflecting common deployment
+ * postures:
+ *
+ * - `strict`: maximum restriction, suitable for admin apps and authenticated
+ *   surfaces. Frame-ancestors none, COOP/CORP same-origin, locked-down
+ *   Permissions-Policy, base-uri/form-action self.
+ * - `moderate`: relaxes CORP to same-site and X-Frame-Options to SAMEORIGIN
+ *   for apps that embed within the same site or allow same-site framing.
+ * - `permissive`: minimal headers (Referrer-Policy + X-Content-Type-Options).
+ *   For public read-only surfaces where CSP would block legitimate behavior.
+ *
+ * `applyDefaultSecurityHeaders` is idempotent — it only sets headers that
+ * are not already present, so consumers can override individual headers
+ * upstream and still benefit from the rest of the preset.
+ */
+
+export type SecurityHeaderPreset = "strict" | "moderate" | "permissive";
+
+export interface SecurityHeadersOptions {
+  /** Which preset to start from. Defaults to "strict". */
+  preset?: SecurityHeaderPreset;
+  /**
+   * Per-header overrides applied on top of the preset.
+   * Pass a string to set a header value.
+   * Pass `null` to remove a header that the preset would otherwise apply.
+   */
+  overrides?: Record<string, string | null>;
+}
+
+const STRICT_HEADERS: Readonly<Record<string, string>> = Object.freeze({
+  "Content-Security-Policy":
+    "base-uri 'self'; form-action 'self'; frame-ancestors 'none'; object-src 'none'",
+  "Cross-Origin-Opener-Policy": "same-origin",
+  "Cross-Origin-Resource-Policy": "same-origin",
+  "Permissions-Policy":
+    "accelerometer=(), camera=(), geolocation=(), gyroscope=(), magnetometer=(), microphone=(), payment=(), usb=()",
+  "Referrer-Policy": "strict-origin-when-cross-origin",
+  "X-Content-Type-Options": "nosniff",
+  "X-Frame-Options": "DENY",
+});
+
+const MODERATE_HEADERS: Readonly<Record<string, string>> = Object.freeze({
+  ...STRICT_HEADERS,
+  "Cross-Origin-Resource-Policy": "same-site",
+  "X-Frame-Options": "SAMEORIGIN",
+});
+
+const PERMISSIVE_HEADERS: Readonly<Record<string, string>> = Object.freeze({
+  "Referrer-Policy": "strict-origin-when-cross-origin",
+  "X-Content-Type-Options": "nosniff",
+});
+
+const PRESETS: Readonly<Record<SecurityHeaderPreset, Readonly<Record<string, string>>>> =
+  Object.freeze({
+    strict: STRICT_HEADERS,
+    moderate: MODERATE_HEADERS,
+    permissive: PERMISSIVE_HEADERS,
+  });
+
+/**
+ * Get the resolved security header map for a preset, with overrides applied.
+ *
+ * Returns a fresh object each call — the caller is free to mutate it.
+ */
+export function getDefaultSecurityHeaders(
+  options: SecurityHeadersOptions = {},
+): Record<string, string> {
+  const { preset = "strict", overrides = {} } = options;
+  const resolved: Record<string, string> = { ...PRESETS[preset] };
+  for (const [key, value] of Object.entries(overrides)) {
+    if (value === null) {
+      delete resolved[key];
+    } else {
+      resolved[key] = value;
+    }
+  }
+  return resolved;
+}
+
+/**
+ * Apply security headers to a Headers object.
+ *
+ * Only sets headers that are not already present, so callers can override
+ * individual headers upstream (e.g. setting CSP per-route) and the preset
+ * fills in the rest.
+ */
+export function applyDefaultSecurityHeaders(
+  headers: Headers,
+  options: SecurityHeadersOptions = {},
+): void {
+  const resolved = getDefaultSecurityHeaders(options);
+  for (const [key, value] of Object.entries(resolved)) {
+    if (!headers.has(key)) {
+      headers.set(key, value);
+    }
+  }
+}
diff --git a/tests/securityHeaders.test.ts b/tests/securityHeaders.test.ts
new file mode 100644
index 0000000..7258824
--- /dev/null
+++ b/tests/securityHeaders.test.ts
@@ -0,0 +1,96 @@
+import { describe, expect, it } from "vitest";
+import {
+  applyDefaultSecurityHeaders,
+  getDefaultSecurityHeaders,
+} from "../src/securityHeaders.js";
+
+describe("getDefaultSecurityHeaders", () => {
+  it("returns the strict preset by default", () => {
+    const headers = getDefaultSecurityHeaders();
+    expect(headers["Content-Security-Policy"]).toContain("frame-ancestors 'none'");
+    expect(headers["X-Frame-Options"]).toBe("DENY");
+    expect(headers["Cross-Origin-Resource-Policy"]).toBe("same-origin");
+  });
+
+  it("relaxes X-Frame-Options and CORP for moderate", () => {
+    const headers = getDefaultSecurityHeaders({ preset: "moderate" });
+    expect(headers["X-Frame-Options"]).toBe("SAMEORIGIN");
+    expect(headers["Cross-Origin-Resource-Policy"]).toBe("same-site");
+    expect(headers["Content-Security-Policy"]).toBeDefined();
+  });
+
+  it("emits only minimal headers for permissive", () => {
+    const headers = getDefaultSecurityHeaders({ preset: "permissive" });
+    expect(headers["Referrer-Policy"]).toBe("strict-origin-when-cross-origin");
+    expect(headers["X-Content-Type-Options"]).toBe("nosniff");
+    expect(headers["Content-Security-Policy"]).toBeUndefined();
+    expect(headers["X-Frame-Options"]).toBeUndefined();
+  });
+
+  it("applies string overrides on top of preset", () => {
+    const headers = getDefaultSecurityHeaders({
+      preset: "strict",
+      overrides: { "X-Frame-Options": "SAMEORIGIN" },
+    });
+    expect(headers["X-Frame-Options"]).toBe("SAMEORIGIN");
+    expect(headers["Cross-Origin-Resource-Policy"]).toBe("same-origin");
+  });
+
+  it("removes headers when override is null", () => {
+    const headers = getDefaultSecurityHeaders({
+      preset: "strict",
+      overrides: { "Content-Security-Policy": null },
+    });
+    expect(headers["Content-Security-Policy"]).toBeUndefined();
+    expect(headers["X-Frame-Options"]).toBe("DENY");
+  });
+
+  it("returns a fresh object each call", () => {
+    const a = getDefaultSecurityHeaders();
+    const b = getDefaultSecurityHeaders();
+    a["Custom"] = "x";
+    expect(b["Custom"]).toBeUndefined();
+  });
+});
+
+describe("applyDefaultSecurityHeaders", () => {
+  it("sets all preset headers on an empty Headers object", () => {
+    const headers = new Headers();
+    applyDefaultSecurityHeaders(headers);
+    expect(headers.get("X-Frame-Options")).toBe("DENY");
+    expect(headers.get("X-Content-Type-Options")).toBe("nosniff");
+    expect(headers.get("Referrer-Policy")).toBe("strict-origin-when-cross-origin");
+  });
+
+  it("does not overwrite existing headers", () => {
+    const headers = new Headers();
+    headers.set("X-Frame-Options", "SAMEORIGIN");
+    applyDefaultSecurityHeaders(headers);
+    expect(headers.get("X-Frame-Options")).toBe("SAMEORIGIN");
+  });
+
+  it("respects preset choice", () => {
+    const headers = new Headers();
+    applyDefaultSecurityHeaders(headers, { preset: "moderate" });
+    expect(headers.get("X-Frame-Options")).toBe("SAMEORIGIN");
+  });
+
+  it("respects overrides", () => {
+    const headers = new Headers();
+    applyDefaultSecurityHeaders(headers, {
+      preset: "strict",
+      overrides: { "X-Custom": "tinyland" },
+    });
+    expect(headers.get("X-Custom")).toBe("tinyland");
+    expect(headers.get("X-Frame-Options")).toBe("DENY");
+  });
+
+  it("removes preset headers when override is null", () => {
+    const headers = new Headers();
+    applyDefaultSecurityHeaders(headers, {
+      overrides: { "Content-Security-Policy": null },
+    });
+    expect(headers.has("Content-Security-Policy")).toBe(false);
+    expect(headers.get("X-Frame-Options")).toBe("DENY");
+  });
+});