diff --git a/src/buildQueryURL.ts b/src/buildQueryURL.ts
index fe862ef9..6588c097 100644
--- a/src/buildQueryURL.ts
+++ b/src/buildQueryURL.ts
@@ -1,6 +1,19 @@
 import { castArray } from "./lib/castArray"
 import { devMsg } from "./lib/devMsg"
 
+import { version } from "../package.json"
+
+/**
+ * The query parameter used to indicate if the client is in development mode to
+ * the API.
+ */
+const PRISMIC_DEV_PARAM = "x-d"
+
+/**
+ * The query parameter used to indicate the version of the client to the API.
+ */
+const PRISMIC_CLIENT_VERSION_PARAM = "x-c"
+
 /**
  * Create a union of the given object's values, and optionally specify which
  * keys to get the values from.
@@ -374,5 +387,11 @@ export const buildQueryURL = (
 		}
 	}
 
+	url.searchParams.set(PRISMIC_CLIENT_VERSION_PARAM, `js-${version}`)
+
+	if (process.env.NODE_ENV === "development") {
+		url.searchParams.set(PRISMIC_DEV_PARAM, "1")
+	}
+
 	return url.toString()
 }
diff --git a/test/buildQueryURL.test.ts b/test/buildQueryURL.test.ts
index 5396d043..4fc5d2b8 100644
--- a/test/buildQueryURL.test.ts
+++ b/test/buildQueryURL.test.ts
@@ -1,12 +1,15 @@
 import { expect, it, vi } from "vitest"
 
+import { version } from "../package.json"
+
 import * as prismic from "../src"
 
 const endpoint = prismic.getRepositoryEndpoint("qwerty")
+const xClientVersionParam = `&x-c=js-${version}`
 
 it("includes ref", () => {
 	expect(prismic.buildQueryURL(endpoint, { ref: "ref" })).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref${xClientVersionParam}`,
 	)
 })
 
@@ -19,7 +22,7 @@ it("supports single filter", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&ref=ref",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&ref=ref${xClientVersionParam}`,
 	)
 
 	// TODO: Remove when we remove support for deprecated `predicates` argument.
@@ -31,7 +34,7 @@ it("supports single filter", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&ref=ref",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&ref=ref${xClientVersionParam}`,
 	)
 })
 
@@ -47,7 +50,7 @@ it("supports multiple filters", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&q=[[has(my.document.subtitle)]]&ref=ref",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&q=[[has(my.document.subtitle)]]&ref=ref${xClientVersionParam}`,
 	)
 
 	// TODO: Remove when we remove support for deprecated `predicates` argument.
@@ -62,7 +65,7 @@ it("supports multiple filters", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&q=[[has(my.document.subtitle)]]&ref=ref",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?q=[[has(my.document.title)]]&q=[[has(my.document.subtitle)]]&ref=ref${xClientVersionParam}`,
 	)
 })
 
@@ -85,7 +88,7 @@ it("supports params", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&access_token=accessToken&pageSize=1&page=1&after=after&fetch=fetch&fetchLinks=fetchLinks&graphQuery=graphQuery&lang=lang&orderings=[orderings]&routes=routes&brokenRoute=brokenRoute",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&access_token=accessToken&pageSize=1&page=1&after=after&fetch=fetch&fetchLinks=fetchLinks&graphQuery=graphQuery&lang=lang&orderings=[orderings]&routes=routes&brokenRoute=brokenRoute${xClientVersionParam}`,
 	)
 })
 
@@ -105,7 +108,9 @@ it("ignores nullish params", () => {
 				orderings: undefined,
 			}),
 		),
-	).toBe("https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref")
+	).toBe(
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref${xClientVersionParam}`,
+	)
 })
 
 it("supports array fetch param", () => {
@@ -117,7 +122,7 @@ it("supports array fetch param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&fetch=title,subtitle",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&fetch=title,subtitle${xClientVersionParam}`,
 	)
 })
 
@@ -130,7 +135,7 @@ it("supports array fetchLinks param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&fetchLinks=page.link,page.second_link",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&fetchLinks=page.link,page.second_link${xClientVersionParam}`,
 	)
 })
 
@@ -144,7 +149,7 @@ it("supports empty orderings param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[]",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[]${xClientVersionParam}`,
 	)
 
 	expect(
@@ -155,7 +160,7 @@ it("supports empty orderings param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[]",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[]${xClientVersionParam}`,
 	)
 })
 
@@ -169,7 +174,7 @@ it("supports array orderings param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[page.title,page.subtitle]",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[page.title,page.subtitle]${xClientVersionParam}`,
 	)
 })
 
@@ -183,7 +188,7 @@ it("supports setting direction of ordering param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[page.title,page.subtitle]",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[page.title,page.subtitle]${xClientVersionParam}`,
 	)
 
 	expect(
@@ -198,7 +203,7 @@ it("supports setting direction of ordering param", () => {
 			}),
 		),
 	).toBe(
-		"https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[page.title+desc,page.subtitle+desc]",
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&orderings=[page.title+desc,page.subtitle+desc]${xClientVersionParam}`,
 	)
 })
 
@@ -219,7 +224,7 @@ it("supports single item routes param", () => {
 	).toBe(
 		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&routes=[${JSON.stringify(
 			route,
-		)}]`,
+		)}]${xClientVersionParam}`,
 	)
 })
 
@@ -247,10 +252,28 @@ it("supports array routes param", () => {
 	).toBe(
 		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref&routes=${JSON.stringify(
 			routes,
-		)}`,
+		)}${xClientVersionParam}`,
 	)
 })
 
+it("forwards `x-c` param in production", () => {
+	expect(prismic.buildQueryURL(endpoint, { ref: "ref" })).toBe(
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref${xClientVersionParam}`,
+	)
+})
+
+it("forwards `x-c` and `x-d` param in development", () => {
+	const originalEnv = { ...process.env }
+
+	process.env.NODE_ENV = "development"
+
+	expect(prismic.buildQueryURL(endpoint, { ref: "ref" })).toBe(
+		`https://qwerty.cdn.prismic.io/api/v2/documents/search?ref=ref${xClientVersionParam}&x-d=1`,
+	)
+
+	process.env = originalEnv
+})
+
 it("warns if NODE_ENV is development and a string is provided to `orderings`", () => {
 	const originalEnv = { ...process.env }
 
diff --git a/test/client-buildQueryURL.test.ts b/test/client-buildQueryURL.test.ts
index 1aff7f14..92a1b730 100644
--- a/test/client-buildQueryURL.test.ts
+++ b/test/client-buildQueryURL.test.ts
@@ -4,8 +4,12 @@ import { createTestClient } from "./__testutils__/createClient"
 import { getMasterRef } from "./__testutils__/getMasterRef"
 import { mockPrismicRestAPIV2 } from "./__testutils__/mockPrismicRestAPIV2"
 
+import { version } from "../package.json"
+
 import type * as prismic from "../src"
 
+const xClientVersion = `js-${version}`
+
 it("builds a query URL using the master ref", async (ctx) => {
 	const repositoryResponse = ctx.mock.api.repository()
 	const ref = getMasterRef(repositoryResponse)
@@ -21,6 +25,7 @@ it("builds a query URL using the master ref", async (ctx) => {
 
 	const expectedSearchParams = new URLSearchParams({
 		ref,
+		"x-c": xClientVersion,
 	})
 	url.searchParams.delete("integrationFieldsRef")
 	url.searchParams.sort()
@@ -31,6 +36,21 @@ it("builds a query URL using the master ref", async (ctx) => {
 	expect(url.searchParams.toString()).toBe(expectedSearchParams.toString())
 })
 
+it("includes the `x-d` param in development", async (ctx) => {
+	const originalEnv = { ...process.env }
+	process.env.NODE_ENV = "development"
+
+	mockPrismicRestAPIV2({ ctx })
+
+	const client = createTestClient()
+	const res = await client.buildQueryURL()
+	const url = new URL(res)
+
+	expect(url.searchParams.get("x-d")).toBe("1")
+
+	process.env = originalEnv
+})
+
 it("includes params if provided", async (ctx) => {
 	const params: prismic.BuildQueryURLArgs = {
 		accessToken: "custom-accessToken",
@@ -49,6 +69,7 @@ it("includes params if provided", async (ctx) => {
 		lang: params.lang?.toString() ?? "",
 		// TODO: Remove when Authorization header support works in browsers with CORS.
 		access_token: params.accessToken ?? "",
+		"x-c": xClientVersion,
 	})
 
 	url.searchParams.delete("integrationFieldsRef")
@@ -78,6 +99,7 @@ it("includes default params if provided", async (ctx) => {
 		lang: clientConfig.defaultParams?.lang?.toString() ?? "",
 		// TODO: Remove when Authorization header support works in browsers with CORS.
 		access_token: clientConfig.accessToken ?? "",
+		"x-c": xClientVersion,
 	})
 
 	url.searchParams.delete("integrationFieldsRef")
@@ -111,6 +133,7 @@ it("merges params and default params if provided", async (ctx) => {
 		page: clientConfig.defaultParams?.page?.toString() ?? "",
 		// TODO: Remove when Authorization header support works in browsers with CORS.
 		access_token: clientConfig.accessToken ?? "",
+		"x-c": xClientVersion,
 	})
 
 	url.searchParams.delete("integrationFieldsRef")