# Selector engines

Playwright supports multiple selector engines used to query elements in the web page.

Selector can be used to obtain `ElementHandle` (see [page.$()](api.md#pageselector) for example) or shortcut element operations to avoid intermediate handle (see [page.click()](api.md#pageclickselector-options) for example).

## Selector syntax

Selector is a string that consists of one or more clauses separated by `>>` token, e.g. `clause1 >> clause2 >> clause3`.  When multiple clauses are present, next one is queried relative to the previous one's result.

Each clause contains a selector engine name and selector body, e.g. `engine=body`. Here `engine` is one of the supported engines (e.g. `css` or a custom one). Selector `body` follows the format of the particular engine, e.g. for `css` engine it should be a [css selector](https://developer.mozilla.org/en/docs/Web/CSS/CSS_Selectors). Body format is assumed to ignore leading and trailing whitespaces, so that extra whitespace can be added for readability. If selector engine needs to include `>>` in the body, it should be escaped inside a string to not be confused with clause separator, e.g. `text="some >> text"`.

For example,
```
css=article >> css=.bar > .baz >> css=span[attr=value]
```
is equivalent to
```js
document
  .querySelector('article')
  .querySelector('.bar > .baz')
  .querySelector('span[attr=value]')
```

For convenience, selectors in the wrong format are heuristically converted to the right format:
- Selector starting with `//` is assumed to be `xpath=selector`. Example: `page.click('//html')` is converted to `page.click('xpath=//html')`.
- Selector starting with `"` is assumed to be `text=selector`. Example: `page.click('"foo"')` is converted to `page.click('text="foo"')`.
- Otherwise, selector is assumed to be `css=selector`. Example: `page.click('div')` is converted to `page.click('css=div')`.

## Examples

```js
// queries 'div' css selector
const handle = await page.$('css=div');

// queries '//html/body/div' xpath selector
const handle = await page.$('xpath=//html/body/div');

// queries '"foo"' text selector
const handle = await page.$('text="foo"');

// queries 'span' css selector inside the result of '//html/body/div' xpath selector
const handle = await page.$('xpath=//html/body/div >> css=span');

// converted to 'css=div'
const handle = await page.$('div');

// converted to 'xpath=//html/body/div'
const handle = await page.$('//html/body/div');

// converted to 'text="foo"'
const handle = await page.$('"foo"');

// queries 'span' css selector inside the div handle
const handle = await divHandle.$('css=span');
```

## Built-in selector engines

### css

CSS engine is equivalent to [`Document.querySelector`](https://developer.mozilla.org/en/docs/Web/API/Document/querySelector). Example: `css=.article > span:nth-child(2) li`.

> **NOTE** Malformed selector not starting with `//` nor with `"` is automatically transformed to css selector. For example, Playwright converts `page.$('span > button')` to `page.$('css=span > button')`. Selectors starting with `"` are converted to [text](#text). Selectors starting with `//` are converted to [xpath](#xpath).

### xpath

XPath engine is equivalent to [`Document.evaluate`](https://developer.mozilla.org/en/docs/Web/API/Document/evaluate). Example: `xpath=//html/body`.

> **NOTE** Malformed selector starting with `//` is automatically transformed to xpath selector. For example, Playwright converts `page.$('//html/body')` to `page.$('xpath=//html/body')`.

### text

Text engine finds an element that contains a text node with passed text. Example: `text=Login`.
- By default, the match is case-insensitive, ignores leading/trailing whitespace and searches for a substring. This means `text= Login` matches `<button>Button loGIN (click me)</button>`.
- Text body can be escaped with double quotes for precise matching, insisting on exact match, including specified whitespace and case. This means `text="Login "` will only match `<button>Login </button>` with exactly one space after "Login".
- Text body can also be a JavaScript-like regex wrapped in `/` symbols. This means `text=/^\\s*Login$/i` will match `<button> loGIN</button>` with any number of spaces before "Login" and no spaces after.

> **NOTE** Text engine first searches for elements in the light dom in the iteration order, and then recursively inside open shadow roots in the iteration order. It does not search inside closed shadow roots or iframes.

> **NOTE** Input elements of the type `button` and `submit` are rendered with their value as text, and text engine finds them. For example, `text=Login` matches `<input type=button value="Login">`.

> **NOTE** Malformed selector starting with `"` is automatically transformed to text selector. For example, Playwright converts `page.click('"Login"')` to `page.click('text="Login"')`.

### deep

Deep engine is equivalent to CSS, but with every [Descendant combinator](https://developer.mozilla.org/en-US/docs/Web/CSS/Descendant_combinator) piercing open shadow roots, including the implicit descendant combinator at the start of the selector. [See this article](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Using_shadow_DOM) for high-level overview of Shadow DOM.

```html
<article>
  <div>In the light dom</div>
  <div slot='myslot'>In the light dom, but goes into the shadow slot</div>
  <open mode shadow root>
    <div class='in-the-shadow'>
      <span class='content'>
        In the shadow dom
        <open mode shadow root>
          <li id='target'>Deep in the shadow</li>
        </open mode shadow root>
      </span>
    </div>
    <slot name='myslot'></slot>
  </open mode shadow root>
</article>
```

Note that `<open mode shadow root>` is not an html element, but rather a shadow root created with `element.attachShadow({mode: 'open'})`.

- `"deep=article div"` matches the first `<div>In the light dom</div>`
- `"deep=article > div"` matches two `div` elements that are direct children of the `article`
- `"deep=article .in-the-shadow"` matches the `<div class='in-the-shadow'>`, piercing the shadow root
- `"deep=article div > span"` matches the `<span class='content'>`, piercing the shadow root
- `"deep=article > .in-the-shadow"` does not match anything, because `<div class='in-the-shadow'>` is not a direct child of `article`
- `"deep=article li#target"` matches the `<li id='target'>Deep in the shadow</li>`, piercing two shadow roots

> **NOTE** Only use deep engine if you need to pierce shadow roots. Otherwise, prefer the more effective CSS engine.

> **NOTE** Deep engine first searches for elements in the light dom in the iteration order, and then recursively inside open shadow roots in the iteration order. It does not search inside closed shadow roots or iframes.

### id, data-testid, data-test-id, data-test

Attribute engines are selecting based on the corresponding atrribute value. For example: `data-test-id=foo` is similar to `deep=[data-test-id="foo"]`.

> **NOTE** Attribute engine first searches for elements in the light dom in the iteration order, and then recursively inside open shadow roots in the iteration order. It does not search inside closed shadow roots or iframes.

## Custom selector engines

Playwright supports custom selector engines, registered with [selectors.register(name, script[, options])](api.md#selectorsregistername-script-options).

Selector engine should have the following properties:

- `create` Function to create a relative selector from `root` (root is either a `Document`, `ShadowRoot` or `Element`) to a `target` element.
- `query` Function to query first element matching `selector` relative to the `root`.
- `queryAll` Function to query all elements matching `selector` relative to the `root`.

By default the engine is run directly in the frame's JavaScript context and, for example, can call an application-defined function. To isolate the engine from any JavaScript in the frame, but leave access to the DOM, resgister the engine with `{contentScript: true}` option. Content script engine is safer because it is protected from any tampering with the global objects, for example altering `Node.prototype` methods. All built-in selector engines run as content scripts. Note that running as a content script is not guaranteed when the engine is used together with other custom engines.

An example of registering selector engine that queries elements based on a tag name:
```js
// Must be a function that evaluates to a selector engine instance.
const createTagNameEngine = () => ({
  // Creates a selector that matches given target when queried at the root.
  // Can return undefined if unable to create one.
  create(root, target) {
    return root.querySelector(target.tagName) === target ? target.tagName : undefined;
  },

  // Returns the first element matching given selector in the root's subtree.
  query(root, selector) {
    return root.querySelector(selector);
  },

  // Returns all elements matching given selector in the root's subtree.
  queryAll(root, selector) {
    return Array.from(root.querySelectorAll(selector));
  }
});

// Register the engine. Selectors will be prefixed with "tag=".
await selectors.register('tag', createTagNameEngine);

// Now we can use 'tag=' selectors.
const button = await page.$('tag=button');

// We can combine it with other selector engines.
await page.click('tag=div >> text="Click me"');

// We can use it in any methods supporting selectors.
const buttonCount = await page.$$eval('tag=button', buttons => buttons.length);
```