docs(test): mention webp as alternative snapshot format in toHaveScreenshot

docs/src/api/class-locatorassertions.md

@@ -1992,6 +1992,9 @@ yield the same result, and then compare the last screenshot with the expectation
 ```js
 const locator = page.getByRole('button');
 await expect(locator).toHaveScreenshot('image.png');
+
+// Store the snapshot in the WebP format.
+await expect(locator).toHaveScreenshot('image.webp');
 ```
 
 Note that screenshot assertions only work with Playwright test runner.
@@ -2000,7 +2003,7 @@ Note that screenshot assertions only work with Playwright test runner.
 * since: v1.23
 - `name` <[string]|[Array]<[string]>>
 
-Snapshot name.
+Snapshot name. Must have a `.png` or `.webp` extension, the screenshot is captured in the corresponding format. Both formats are lossless.
 
 ### option: LocatorAssertions.toHaveScreenshot#1.timeout = %%-js-assertions-timeout-%%
 * since: v1.23
@@ -2042,6 +2045,8 @@ Snapshot name.
 This function will wait until two consecutive locator screenshots
 yield the same result, and then compare the last screenshot with the expectation.
 
+The snapshot is stored in the PNG format. To store it in the WebP format instead, pass a snapshot name with the `.webp` extension.
+
 **Usage**
 
 ```js

docs/src/api/class-pageassertions.md

@@ -242,6 +242,9 @@ yield the same result, and then compare the last screenshot with the expectation
 
 ```js
 await expect(page).toHaveScreenshot('image.png');
+
+// Store the snapshot in the WebP format.
+await expect(page).toHaveScreenshot('image.webp');
 ```
 
 Note that screenshot assertions only work with Playwright test runner.
@@ -250,7 +253,7 @@ Note that screenshot assertions only work with Playwright test runner.
 * since: v1.23
 - `name` <[string]|[Array]<[string]>>
 
-Snapshot name.
+Snapshot name. Must have a `.png` or `.webp` extension, the screenshot is captured in the corresponding format. Both formats are lossless.
 
 ### option: PageAssertions.toHaveScreenshot#1.timeout = %%-js-assertions-timeout-%%
 * since: v1.23
@@ -298,6 +301,8 @@ Snapshot name.
 This function will wait until two consecutive page screenshots
 yield the same result, and then compare the last screenshot with the expectation.
 
+The snapshot is stored in the PNG format. To store it in the WebP format instead, pass a snapshot name with the `.webp` extension.
+
 **Usage**
 
 ```js

docs/src/test-snapshots-js.md

@@ -50,6 +50,12 @@ The snapshot name `example-test-1-chromium-darwin.png` consists of a few parts:
 
 The snapshot name and path can be configured with [`property: TestConfig.snapshotPathTemplate`] in the playwright config.
 
+Snapshots are stored as PNG by default. Give the snapshot a name with the `.webp` extension to store it in the WebP format instead, it is also lossless:
+
+```js
+await expect(page).toHaveScreenshot('landing.webp');
+```
+
 > Note that `toHaveScreenshot()` also accepts an array of path segments to the snapshot file such as `expect().toHaveScreenshot(['relative', 'path', 'to', 'snapshot.png'])`.
 > However, this path must stay within the snapshots directory for each test file (i.e. `a.spec.js-snapshots`), otherwise it will throw.
 

packages/playwright/types/test.d.ts

@@ -9549,10 +9549,14 @@ interface LocatorAssertions {
    * ```js
    * const locator = page.getByRole('button');
    * await expect(locator).toHaveScreenshot('image.png');
+   *
+   * // Store the snapshot in the WebP format.
+   * await expect(locator).toHaveScreenshot('image.webp');
    * ```
    *
    * Note that screenshot assertions only work with Playwright test runner.
-   * @param name Snapshot name.
+   * @param name Snapshot name. Must have a `.png` or `.webp` extension, the screenshot is captured in the corresponding format.
+   * Both formats are lossless.
    * @param options
    */
   toHaveScreenshot(name: string|ReadonlyArray<string>, options?: {
@@ -9638,6 +9642,9 @@ interface LocatorAssertions {
    * This function will wait until two consecutive locator screenshots yield the same result, and then compare the last
    * screenshot with the expectation.
    *
+   * The snapshot is stored in the PNG format. To store it in the WebP format instead, pass a snapshot name with the
+   * `.webp` extension.
+   *
    * **Usage**
    *
    * ```js
@@ -9976,10 +9983,14 @@ interface PageAssertions {
    *
    * ```js
    * await expect(page).toHaveScreenshot('image.png');
+   *
+   * // Store the snapshot in the WebP format.
+   * await expect(page).toHaveScreenshot('image.webp');
    * ```
    *
    * Note that screenshot assertions only work with Playwright test runner.
-   * @param name Snapshot name.
+   * @param name Snapshot name. Must have a `.png` or `.webp` extension, the screenshot is captured in the corresponding format.
+   * Both formats are lossless.
    * @param options
    */
   toHaveScreenshot(name: string|ReadonlyArray<string>, options?: PageAssertionsToHaveScreenshotOptions): Promise<void>;
@@ -9988,6 +9999,9 @@ interface PageAssertions {
    * This function will wait until two consecutive page screenshots yield the same result, and then compare the last
    * screenshot with the expectation.
    *
+   * The snapshot is stored in the PNG format. To store it in the WebP format instead, pass a snapshot name with the
+   * `.webp` extension.
+   *
    * **Usage**
    *
    * ```js