diff --git a/src/blog.ts b/lib/blog.d.ts
similarity index 58%
rename from src/blog.ts
rename to lib/blog.d.ts
index 905ceb4..2cb85ec 100644
--- a/src/blog.ts
+++ b/lib/blog.d.ts
@@ -11,7 +11,7 @@ export class Blog {
 	/**
 	 * The languages in use on the blog or site, in ISO 639-1 format.
 	 */
-	languages: Array<string>;
+	languages: Set<string>;
 
 	/**
 	 * The blog or site URL.
@@ -22,35 +22,20 @@ export class Blog {
 	 * Creates a new blog.
 	 * @param options An object providing values to initialize this instance.
 	 */
-	constructor(options: BlogOptions = {}) {
-		this.charset = options.charset ?? "";
-		this.languages = options.languages ?? [];
-		this.url = options.url ? new URL(options.url) : null;
-	}
+	constructor(options?: BlogOptions);
 
 	/**
 	 * Creates a new blog from the specified JSON object.
 	 * @param json A JSON object representing a blog.
 	 * @returns The instance corresponding to the specified JSON object.
 	 */
-	static fromJson(json: Record<string, any>): Blog {
-		return new this({
-			charset: typeof json.blog_charset == "string" ? json.blog_charset : "",
-			languages: typeof json.blog_lang == "string" ? json.blog_lang.split(",").map(language => language.trim()) : [],
-			url: typeof json.blog == "string" ? json.blog : ""
-		});
-	}
+	static fromJson(json: Record<string, any>): Blog;
 
 	/**
 	 * Returns a JSON representation of this object.
 	 * @returns The JSON representation of this object.
 	 */
-	toJSON(): Record<string, any> {
-		const map: Record<string, any> = {blog: this.url?.href ?? ""};
-		if (this.charset) map.blog_charset = this.charset;
-		if (this.languages.length) map.blog_lang = this.languages.join();
-		return map;
-	}
+	toJSON(): Record<string, any>;
 }
 
 /**
diff --git a/src/blog.coffee b/src/blog.coffee
new file mode 100644
index 0000000..6a6364e
--- /dev/null
+++ b/src/blog.coffee
@@ -0,0 +1,27 @@
+# Represents the front page or home URL transmitted when making requests.
+export class Blog
+
+	# Creates a new blog.
+	constructor: (options = {}) ->
+
+		# The character encoding for the values included in comments.
+		@charset = options.charset ? ""
+
+		# The languages in use on the blog or site, in ISO 639-1 format.
+		@languages = new Set(options.languages ? [])
+
+		# The blog or site URL.
+		@url = if options.url then new URL options.url else null
+
+	# Creates a new blog from the specified JSON object.
+	@fromJson: (json) -> new @
+		charset: if typeof json.blog_charset == "string" then json.blog_charset else ""
+		languages: if typeof json.blog_lang == "string" then json.blog_lang.split(",").map (language) -> language.trim() else []
+		url: if typeof json.blog == "string" then json.blog else ""
+
+	# Returns a JSON representation of this object.
+	toJSON: ->
+		map = blog: @url?.href ? ""
+		map.blog_charset = @charset if @charset
+		map.blog_lang = Array.from(@languages).join "," if @languages.size
+		map
diff --git a/test/blog_test.coffee b/test/blog_test.coffee
new file mode 100644
index 0000000..d8f3f2a
--- /dev/null
+++ b/test/blog_test.coffee
@@ -0,0 +1,36 @@
+import {Blog} from "@cedx/akismet"
+import {deepEqual, equal, ok} from "node:assert/strict"
+import {describe, it} from "node:test"
+
+# Tests the features of the `Blog` class.
+describe "Blog", ->
+	describe "fromJson()", ->
+		it "should return an empty instance with an empty map", ->
+			blog = Blog.fromJson {}
+			equal blog.charset.length, 0
+			equal blog.languages.length, 0
+			equal blog.url, null
+
+		it "should return an initialized instance with a non-empty map", ->
+			blog = Blog.fromJson
+				blog: "https://github.com/cedx/akismet.js"
+				blog_charset: "UTF-8"
+				blog_lang: "en, fr"
+
+			equal blog.charset, "UTF-8"
+			deepEqual blog.languages, ["en", "fr"]
+			ok blog.url instanceof URL
+			equal blog.url.href, "https://github.com/cedx/akismet.js"
+
+	describe "toJSON()", ->
+		it "should return only the blog URL with a newly created instance", ->
+			json = new Blog(url: "https://github.com/cedx/akismet.js").toJSON()
+			equal Object.keys(json).length, 1
+			equal json.blog, "https://github.com/cedx/akismet.js"
+
+		it "should return a non-empty map with an initialized instance", ->
+			json = new Blog(charset: "UTF-8", languages: ["en", "fr"], url: "https://github.com/cedx/akismet.js").toJSON()
+			equal Object.keys(json).length, 3
+			equal json.blog, "https://github.com/cedx/akismet.js"
+			equal json.blog_charset, "UTF-8"
+			equal json.blog_lang, "en,fr"
diff --git a/test/blog_test.js b/test/blog_test.js
deleted file mode 100644
index e99ce57..0000000
--- a/test/blog_test.js
+++ /dev/null
@@ -1,46 +0,0 @@
-import {Blog} from "@cedx/akismet";
-import {deepEqual, equal, ok} from "node:assert/strict";
-import {describe, it} from "node:test";
-
-/**
- * Tests the features of the {@link Blog} class.
- */
-describe("Blog", () => {
-	describe("fromJson()", () => {
-		it("should return an empty instance with an empty map", () => {
-			const blog = Blog.fromJson({});
-			equal(blog.charset.length, 0);
-			equal(blog.languages.length, 0);
-			equal(blog.url, null);
-		});
-
-		it("should return an initialized instance with a non-empty map", () => {
-			const blog = Blog.fromJson({
-				blog: "https://github.com/cedx/akismet.js",
-				blog_charset: "UTF-8",
-				blog_lang: "en, fr"
-			});
-
-			equal(blog.charset, "UTF-8");
-			deepEqual(blog.languages, ["en", "fr"]);
-			ok(blog.url instanceof URL);
-			equal(blog.url.href, "https://github.com/cedx/akismet.js");
-		});
-	});
-
-	describe("toJSON()", () => {
-		it("should return only the blog URL with a newly created instance", () => {
-			const json = new Blog({url: "https://github.com/cedx/akismet.js"}).toJSON();
-			equal(Object.keys(json).length, 1);
-			equal(json.blog, "https://github.com/cedx/akismet.js");
-		});
-
-		it("should return a non-empty map with an initialized instance", () => {
-			const json = new Blog({charset: "UTF-8", languages: ["en", "fr"], url: "https://github.com/cedx/akismet.js"}).toJSON();
-			equal(Object.keys(json).length, 3);
-			equal(json.blog, "https://github.com/cedx/akismet.js");
-			equal(json.blog_charset, "UTF-8");
-			equal(json.blog_lang, "en,fr");
-		});
-	});
-});