diff --git a/docs/src/api/class-locatorassertions.md b/docs/src/api/class-locatorassertions.md
index 1d4b4b2890..a76aa1a964 100644
--- a/docs/src/api/class-locatorassertions.md
+++ b/docs/src/api/class-locatorassertions.md
@@ -91,56 +91,64 @@ await Expect(locator).Not.ToContainTextAsync("error");
 
 The opposite of [`method: LocatorAssertions.toBeChecked`].
 
-### option: LocatorAssertions.NotToBeChecked.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeChecked.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeChecked.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeDisabled
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeDisabled`].
 
-### option: LocatorAssertions.NotToBeDisabled.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeDisabled.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeDisabled.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeEditable
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeEditable`].
 
-### option: LocatorAssertions.NotToBeEditable.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeEditable.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeEditable.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeEmpty
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeEmpty`].
 
-### option: LocatorAssertions.NotToBeEmpty.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeEmpty.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeEmpty.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeEnabled
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeEnabled`].
 
-### option: LocatorAssertions.NotToBeEnabled.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeEnabled.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeEnabled.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeFocused
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeFocused`].
 
-### option: LocatorAssertions.NotToBeFocused.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeFocused.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeFocused.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeHidden
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeHidden`].
 
-### option: LocatorAssertions.NotToBeHidden.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeHidden.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeHidden.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToBeVisible
 * langs: python
 
 The opposite of [`method: LocatorAssertions.toBeVisible`].
 
-### option: LocatorAssertions.NotToBeVisible.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeVisible.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToBeVisible.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.NotToContainText
@@ -158,7 +166,8 @@ Expected substring or RegExp or a list of those.
 
 Whether to use `element.innerText` instead of `element.textContent` when retrieving DOM node text.
 
-### option: LocatorAssertions.NotToContainText.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToContainText.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToContainText.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveAttribute
 * langs: python
@@ -175,7 +184,8 @@ Attribute name.
 
 Expected attribute value.
 
-### option: LocatorAssertions.NotToHaveAttribute.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveAttribute.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveAttribute.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveClass
 * langs: python
@@ -187,7 +197,8 @@ The opposite of [`method: LocatorAssertions.toHaveClass`].
 
 Expected class or RegExp or a list of those.
 
-### option: LocatorAssertions.NotToHaveClass.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveClass.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveClass.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveCount
 * langs: python
@@ -199,7 +210,8 @@ The opposite of [`method: LocatorAssertions.toHaveCount`].
 
 Expected count.
 
-### option: LocatorAssertions.NotToHaveCount.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveCount.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveCount.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveCSS
 * langs: python
@@ -216,7 +228,8 @@ CSS property name.
 
 CSS property value.
 
-### option: LocatorAssertions.NotToHaveCSS.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveCSS.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveCSS.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveId
 * langs: python
@@ -228,7 +241,8 @@ The opposite of [`method: LocatorAssertions.toHaveId`].
 
 Element id.
 
-### option: LocatorAssertions.NotToHaveId.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveId.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveId.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveJSProperty
 * langs: python
@@ -245,7 +259,8 @@ Property name.
 
 Property value.
 
-### option: LocatorAssertions.NotToHaveJSProperty.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveJSProperty.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveJSProperty.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveText
 * langs: python
@@ -262,7 +277,8 @@ Expected substring or RegExp or a list of those.
 
 Whether to use `element.innerText` instead of `element.textContent` when retrieving DOM node text.
 
-### option: LocatorAssertions.NotToHaveText.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveText.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveText.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.NotToHaveValue
 * langs: python
@@ -274,7 +290,8 @@ The opposite of [`method: LocatorAssertions.toHaveValue`].
 
 Expected value.
 
-### option: LocatorAssertions.NotToHaveValue.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveValue.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.NotToHaveValue.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeChecked
@@ -314,7 +331,8 @@ await Expect(locator).ToBeCheckedAsync();
 ### option: LocatorAssertions.toBeChecked.checked
 - `checked` <[boolean]>
 
-### option: LocatorAssertions.toBeChecked.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeChecked.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeChecked.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeDisabled
@@ -351,7 +369,8 @@ var locator = Page.Locator("button.submit");
 await Expect(locator).ToBeDisabledAsync();
 ```
 
-### option: LocatorAssertions.toBeDisabled.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeDisabled.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeDisabled.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeEditable
@@ -388,7 +407,8 @@ var locator = Page.Locator("input");
 await Expect(locator).ToBeEditableAsync();
 ```
 
-### option: LocatorAssertions.toBeEditable.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeEditable.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeEditable.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeEmpty
@@ -425,7 +445,8 @@ var locator = Page.Locator("div.warning");
 await Expect(locator).ToBeEmptyAsync();
 ```
 
-### option: LocatorAssertions.toBeEmpty.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeEmpty.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeEmpty.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeEnabled
@@ -462,7 +483,8 @@ var locator = Page.Locator("button.submit");
 await Expect(locator).toBeEnabledAsync();
 ```
 
-### option: LocatorAssertions.toBeEnabled.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeEnabled.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeEnabled.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeFocused
@@ -499,7 +521,8 @@ var locator = Page.Locator("input");
 await Expect(locator).ToBeFocusedAsync();
 ```
 
-### option: LocatorAssertions.toBeFocused.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeFocused.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeFocused.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeHidden
@@ -536,7 +559,8 @@ var locator = Page.Locator(".my-element");
 await Expect(locator).ToBeHiddenAsync();
 ```
 
-### option: LocatorAssertions.toBeHidden.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeHidden.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeHidden.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toBeVisible
@@ -573,7 +597,8 @@ var locator = Page.Locator(".my-element");
 await Expect(locator).ToBeVisibleAsync();
 ```
 
-### option: LocatorAssertions.toBeVisible.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toBeVisible.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toBeVisible.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.toContainText
 * langs:
@@ -664,7 +689,8 @@ Expected substring or RegExp or a list of those.
 
 Whether to use `element.innerText` instead of `element.textContent` when retrieving DOM node text.
 
-### option: LocatorAssertions.toContainText.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toContainText.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toContainText.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toHaveAttribute
@@ -711,7 +737,8 @@ Attribute name.
 
 Expected attribute value.
 
-### option: LocatorAssertions.toHaveAttribute.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveAttribute.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveAttribute.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.toHaveClass
 * langs:
@@ -789,7 +816,8 @@ Expected class or RegExp or a list of those.
 
 Expected class or RegExp or a list of those.
 
-### option: LocatorAssertions.toHaveClass.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveClass.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveClass.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toHaveCount
@@ -831,7 +859,8 @@ await Expect(locator).ToHaveCountAsync(3);
 
 Expected count.
 
-### option: LocatorAssertions.toHaveCount.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveCount.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveCount.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.toHaveCSS
 * langs:
@@ -877,7 +906,8 @@ CSS property name.
 
 CSS property value.
 
-### option: LocatorAssertions.toHaveCSS.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveCSS.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveCSS.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.toHaveId
 * langs:
@@ -918,7 +948,8 @@ await Expect(locator).ToHaveIdAsync("lastname");
 
 Element id.
 
-### option: LocatorAssertions.toHaveId.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveId.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveId.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 
 ## async method: LocatorAssertions.toHaveJSProperty
@@ -966,7 +997,8 @@ Property name.
 
 Property value.
 
-### option: LocatorAssertions.toHaveJSProperty.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveJSProperty.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveJSProperty.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.toHaveScreenshot
 * langs: js
@@ -982,7 +1014,8 @@ const locator = page.locator('button');
 await expect(locator).toHaveScreenshot();
 ```
 
-### option: LocatorAssertions.toHaveScreenshot.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveScreenshot.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveScreenshot.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ### option: LocatorAssertions.toHaveScreenshot.disableAnimations = %%-screenshot-option-disable-animations-%%
 
@@ -1086,7 +1119,8 @@ Expected substring or RegExp or a list of those.
 
 Whether to use `element.innerText` instead of `element.textContent` when retrieving DOM node text.
 
-### option: LocatorAssertions.toHaveText.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveText.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveText.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: LocatorAssertions.toHaveValue
 * langs:
@@ -1129,4 +1163,5 @@ await Expect(locator).ToHaveValueAsync(new Regex("[0-9]"));
 
 Expected value.
 
-### option: LocatorAssertions.toHaveValue.timeout = %%-assertions-timeout-%%
+### option: LocatorAssertions.toHaveValue.timeout = %%-js-assertions-timeout-%%
+### option: LocatorAssertions.toHaveValue.timeout = %%-csharp-java-python-assertions-timeout-%%
diff --git a/docs/src/api/class-pageassertions.md b/docs/src/api/class-pageassertions.md
index 49019c01bb..266a134477 100644
--- a/docs/src/api/class-pageassertions.md
+++ b/docs/src/api/class-pageassertions.md
@@ -99,7 +99,8 @@ The opposite of [`method: PageAssertions.toHaveTitle`].
 
 Expected title or RegExp.
 
-### option: PageAssertions.NotToHaveTitle.timeout = %%-assertions-timeout-%%
+### option: PageAssertions.NotToHaveTitle.timeout = %%-js-assertions-timeout-%%
+### option: PageAssertions.NotToHaveTitle.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: PageAssertions.NotToHaveURL
 * langs: python
@@ -112,7 +113,8 @@ The opposite of [`method: PageAssertions.toHaveURL`].
 
 Expected substring or RegExp.
 
-### option: PageAssertions.NotToHaveURL.timeout = %%-assertions-timeout-%%
+### option: PageAssertions.NotToHaveURL.timeout = %%-js-assertions-timeout-%%
+### option: PageAssertions.NotToHaveURL.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: PageAssertions.toHaveScreenshot
 * langs: js
@@ -127,7 +129,8 @@ yield the same result, and save the last one as an expectation.
 await expect(page).toHaveScreenshot();
 ```
 
-### option: PageAssertions.toHaveScreenshot.timeout = %%-assertions-timeout-%%
+### option: PageAssertions.toHaveScreenshot.timeout = %%-js-assertions-timeout-%%
+### option: PageAssertions.toHaveScreenshot.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ### option: PageAssertions.toHaveScreenshot.disableAnimations = %%-screenshot-option-disable-animations-%%
 
@@ -184,7 +187,8 @@ await Expect(page).ToHaveTitle("Playwright");
 
 Expected title or RegExp.
 
-### option: PageAssertions.toHaveTitle.timeout = %%-assertions-timeout-%%
+### option: PageAssertions.toHaveTitle.timeout = %%-js-assertions-timeout-%%
+### option: PageAssertions.toHaveTitle.timeout = %%-csharp-java-python-assertions-timeout-%%
 
 ## async method: PageAssertions.toHaveURL
 * langs:
@@ -225,4 +229,5 @@ await Expect(page).ToHaveURL(new Regex(".*checkout"));
 
 Expected substring or RegExp.
 
-### option: PageAssertions.toHaveURL.timeout = %%-assertions-timeout-%%
+### option: PageAssertions.toHaveURL.timeout = %%-js-assertions-timeout-%%
+### option: PageAssertions.toHaveURL.timeout = %%-csharp-java-python-assertions-timeout-%%
diff --git a/docs/src/api/params.md b/docs/src/api/params.md
index 8da0274650..691eebcfa5 100644
--- a/docs/src/api/params.md
+++ b/docs/src/api/params.md
@@ -703,31 +703,36 @@ The default value can be changed by using the [`method: BrowserContext.setDefaul
 Maximum time in milliseconds, defaults to 30 seconds, pass `0` to disable timeout. The default value can be changed by
 using the [`method: AndroidDevice.setDefaultTimeout`] method.
 
-## assertions-timeout
+## js-assertions-timeout
 * langs: js
 - `timeout` <[float]>
 
-Time to retry the assertion for. Defaults to `timeout` in [`property: TestConfig.expect`].
+Time to retry the assertion for. Defaults to `timeout` in `TestConfig.expect`.
 
-## assertions-pixel-count
-* langs: js
-- `pixelCount` <[int]> an acceptable amount of pixels that could be different, unset by default.
-
-## assertions-pixel-ratio
-* langs: js
-- `pixelRatio` <[float]> an acceptable ratio of pixels that are different to the total amount of pixels, between `0` and `1`, unset by default.
-
-## assertions-threshold
-* langs: js
-- `threshold` <[float]> an acceptable percieved color difference in the [YIQ color space](https://en.wikipedia.org/wiki/YIQ) between pixels in compared images, between zero (strict) and one (lax), default is configurable with [`property: TestConfig.expect`]. Defaults to `0.2`.
-
-
-## assertions-timeout
+## csharp-java-python-assertions-timeout
 * langs: java, python, csharp
 - `timeout` <[float]>
 
 Time to retry the assertion for.
 
+## assertions-pixel-count
+* langs: js
+- `pixelCount` <[int]>
+
+An acceptable amount of pixels that could be different, unset by default.
+
+## assertions-pixel-ratio
+* langs: js
+- `pixelRatio` <[float]>
+
+An acceptable ratio of pixels that are different to the total amount of pixels, between `0` and `1`, unset by default.
+
+## assertions-threshold
+* langs: js
+- `threshold` <[float]>
+
+An acceptable percieved color difference in the [YIQ color space](https://en.wikipedia.org/wiki/YIQ) between pixels in compared images, between zero (strict) and one (lax), default is configurable with `TestConfig.expect`. Defaults to `0.2`.
+
 ## shared-context-params-list
 - %%-context-option-acceptdownloads-%%
 - %%-context-option-ignorehttpserrors-%%
diff --git a/utils/doclint/api_parser.js b/utils/doclint/api_parser.js
index a05faee9eb..daf2529ad8 100644
--- a/utils/doclint/api_parser.js
+++ b/utils/doclint/api_parser.js
@@ -40,6 +40,7 @@ class ApiParser {
     }
     const body = md.parse(bodyParts.join('\n'));
     const params = paramsPath ? md.parse(fs.readFileSync(paramsPath).toString()) : null;
+    checkNoDuplicateParamEntries(params);
     const api = params ? applyTemplates(body, params) : body;
     /** @type {Map<string, Documentation.Class>} */
     this.classes = new Map();
@@ -371,4 +372,18 @@ function isTypeOverride(existingMember, member) {
   return false;
 }
 
+/**
+ * @param {MarkdownNode[]=} params
+ */
+function checkNoDuplicateParamEntries(params) {
+  if (!params)
+    return;
+  const entries = new Set();
+  for (const node of params) {
+    if (entries.has(node.text))
+      throw new Error('Duplicate param entry, for language-specific params use prefix (e.g. js-...): ' + node.text);
+    entries.add(node.text);
+  }
+}
+
 module.exports = { parseApi };