diff --git a/CHANGES.md b/CHANGES.md
index fab3f36..54f6b6c 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,3 +1,7 @@
+## Unreleased
+
+* Added `tinify.Format` constants for the media types `convert` accepts. `SupportedImageTypes` is now derived from them.
+
 ## 1.8.3
 * add JXL to supported image formats
 * add node 26 as test target
diff --git a/README.md b/README.md
index 675f503..82d91ea 100644
--- a/README.md
+++ b/README.md
@@ -5,11 +5,11 @@
 
 # Tinify API client for Node.js
 
-A lightweight Node.js client for the Tinify API, used for [tinypng API](https://tinypng.com) and [TinyJPG](https://tinyjpg.com). This library lets you intelligently **compress**, **resize**, **convert**, and **store** images (AVIF, WebP, JPEG, PNG) with minimal effort. Read more at [http://tinify.com](http://tinify.com).
+A lightweight Node.js client for the Tinify API, used for [tinypng API](https://tinypng.com) and [TinyJPG](https://tinyjpg.com). This library lets you intelligently **compress**, **resize**, **convert**, and **store** images (AVIF, JXL, WebP, JPEG, PNG) with minimal effort. Read more at [http://tinify.com](http://tinify.com).
 
 ## 🚀 Features
 
-- Compress and optimize images in AVIF, WebP, JPEG, and PNG formats
+- Compress and optimize images in AVIF, JXL, WebP, JPEG, and PNG formats
 - Resize with intelligent cropping
 - Convert between formats
 - Preserve metadata (copyright, GPS, creation time)
diff --git a/src/index.ts b/src/index.ts
index b17619d..10e3af7 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,6 +1,7 @@
 import tinify from "./tinify"
 
 import Client from "./tinify/Client"
+import Format from "./tinify/Format"
 import Result from "./tinify/Result"
 import ResultMeta from "./tinify/ResultMeta"
 import Source from "./tinify/Source"
@@ -14,6 +15,7 @@ import {
 } from "./tinify/Error"
 
 tinify.Client = Client
+tinify.Format = Format
 tinify.ResultMeta = ResultMeta
 tinify.Result = Result
 tinify.Source = Source
diff --git a/src/tinify.ts b/src/tinify.ts
index 5027434..db73199 100644
--- a/src/tinify.ts
+++ b/src/tinify.ts
@@ -1,6 +1,7 @@
 import {nodeify, Callback} from "./tinify/compat"
 
 import Client from "./tinify/Client"
+import Format from "./tinify/Format"
 import Result from "./tinify/Result"
 import ResultMeta from "./tinify/ResultMeta"
 import Source from "./tinify/Source"
@@ -19,6 +20,7 @@ class Tinify {
   compressionCount?: number
 
   Client!: typeof Client
+  Format!: typeof Format
   Source!: typeof Source
   Result!: typeof Result
   ResultMeta!: typeof ResultMeta
diff --git a/src/tinify/Format.ts b/src/tinify/Format.ts
new file mode 100644
index 0000000..9dfafa2
--- /dev/null
+++ b/src/tinify/Format.ts
@@ -0,0 +1,42 @@
+/**
+ * Media types that images can be converted to.
+ *
+ * ```js
+ * const tinify = require("tinify")
+ *
+ * tinify.fromFile("input.png")
+ *   .convert({type: tinify.Format.JXL})
+ *   .toFile("output.jxl")
+ * ```
+ *
+ * Multiple types may be supplied, in which case the API returns the smallest
+ * result:
+ *
+ * ```js
+ * .convert({type: [tinify.Format.JXL, tinify.Format.WEBP]})
+ * ```
+ */
+const Format = {
+  /** WebP. */
+  WEBP: "image/webp",
+
+  /** PNG. */
+  PNG: "image/png",
+
+  /** JPEG. */
+  JPEG: "image/jpeg",
+
+  /** JPEG, an alias of `JPEG`. */
+  JPG: "image/jpg",
+
+  /** AVIF. */
+  AVIF: "image/avif",
+
+  /** JPEG XL. */
+  JXL: "image/jxl",
+
+  /** Wildcard, returns the smallest of the supported types. */
+  ANY: "*/*",
+} as const
+
+export default Format
diff --git a/src/tinify/Source.ts b/src/tinify/Source.ts
index e1fab71..3b5a924 100644
--- a/src/tinify/Source.ts
+++ b/src/tinify/Source.ts
@@ -2,18 +2,17 @@ import tinify from "../tinify"
 import {readFile, Callback} from "./compat"
 
 import Client from "./Client"
+import Format from "./Format"
 import Result from "./Result"
 import ResultMeta from "./ResultMeta"
 
-export type SupportedImageTypes = "image/webp"
-  | "image/png"
-  | "image/jpg"
-  | "image/jpeg"
-  | "image/jxl"
-  | "image/avif";
+type FormatValues = (typeof Format)[keyof typeof Format];
 
+export type SupportedImageTypes = Exclude<FormatValues, typeof Format.ANY>;
+
+// The wildcard "*/*" returns the smallest of Tinify's supported image types.
 export type WildcardOrSupportedImageTypes = SupportedImageTypes
-  | "*/*"; // The wildcard "*/*" returns the smallest of Tinify's supported image types, currently JPEG, PNG and WebP.
+  | typeof Format.ANY;
 
 export type ConvertOptions = {
   type: WildcardOrSupportedImageTypes | SupportedImageTypes[];
diff --git a/test/tinify-typing-test.ts b/test/tinify-typing-test.ts
index bc2311e..06b9078 100644
--- a/test/tinify-typing-test.ts
+++ b/test/tinify-typing-test.ts
@@ -15,8 +15,17 @@ async function run() {
     await tinify.fromFile("/foo/bar").convert({ type: "image/webp" })
     await tinify.fromFile("/foo/bar").convert({ type: "image/png" })
     await tinify.fromFile("/foo/bar").convert({ type: "image/jpg" })
+    await tinify.fromFile("/foo/bar").convert({ type: "image/jxl" })
+    await tinify.fromFile("/foo/bar").convert({ type: "image/avif" })
     await tinify.fromFile("/foo/bar").convert({ type: "*/*" })
 
+    // The Format constants are accepted everywhere a literal is.
+    await tinify.fromFile("/foo/bar").convert({ type: tinify.Format.JXL })
+    await tinify.fromFile("/foo/bar").convert({ type: tinify.Format.ANY })
+    await tinify.fromFile("/foo/bar").convert({
+      type: [tinify.Format.JXL, tinify.Format.WEBP],
+    })
+
     await tinify.fromBuffer("foo")
       .resize({method: "fit", width: 150, height: 100})
       .preserve("copyright", "creation")