> For the complete documentation index, see [llms.txt](https://docs.pylenium.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.pylenium.io/driver-commands/web-performance/performance-api.md).

# Performance API

## Syntax

```python
py.performance -> Performance
py.performance.get() -> WebPerformance
```

## Usage

The <mark style="color:orange;">**Performance**</mark> class is where everything lives. It provides access to the following methods:

### WebPerformance

The main method used to generate a <mark style="color:orange;">**WebPerformance**</mark> object from the current web page. This is really all you need from this API and will be discussed in more detail [further below in Metrics](#metrics).

{% hint style="danger" %}
Calling this method too soon may yield NoneTypes because the browser hasn't generated them yet.
{% endhint %}

```python
py.performance.get() -> WebPerformance
```

### Time Origin

Return the <mark style="color:yellow;">**timeOrigin**</mark> precision value. This is the high-resolution timestamp of the start time of the performance measurement.

```python
py.performance.get_time_origin() -> float
```

### Navigation Timing

Return the <mark style="color:yellow;">**PerformanceNavigationTiming**</mark> W3 object as a Python object called <mark style="color:orange;">**NavigationTiming**</mark>.

```python
py.performance.get_navigation_timing() -> NavigationTiming
```

### Paint Timing

Return the <mark style="color:yellow;">**PerformancePaintTiming**</mark> object as a Python object called <mark style="color:orange;">**PaintTiming**</mark>.

```python
py.performance.get_paint_timing() -> PaintTiming
```

### Resources

Return a list of <mark style="color:yellow;">**PerformanceResourceTiming**</mark> objects as Python objects called <mark style="color:orange;">**\[ResourceTiming]**</mark>.

```python
py.performance.get_resources() -> List[ResourceTiming]
```

## Metrics

All of the timing objects include A LOT of data points, but many of them may not be useful.

{% hint style="info" %}
If you want to see ALL the data points, take a look at [the file in the GitHub Repo](https://github.com/ElSnoMan/pyleniumio/blob/main/pylenium/performance.py)
{% endhint %}

This is why the <mark style="color:orange;">**WebPerformance**</mark> object exists! It contains calculations for metrics that have been very useful when we talk about and measure web performance. After navigating to a website and capturing these metrics with <mark style="color:purple;">`py.performance.get()`</mark>, we can do whatever we want with them!

With a few lines of code, you have access to many valuable metrics:

```python
# perf will be used in the examples below
py.visit("https://your-website.com")
perf = py.performance.get()
```

### Page Load Time

The time it takes for the page to load as experienced by the user.

```python
perf.page_load_time() -> float
```

### Time to First Byte

The time it takes before the first byte of response is received from the server.

```python
perf.time_to_first_byte() -> float
```

### Time to First Contentful Paint

The time it takes for the majority of content to be fully rendered and consumable by the user.

```python
perf.time_to_first_contentful_paint() -> float
```

### Time to Interactive (TTI)

The time it takes for the layout to be stabilized and the page is responsive.

```python
perf.time_to_interactive() -> float
```

### Number of Requests

The number of requests sent from start of navigation until end of page load.

```python
perf.number_of_requests() -> int
```

### Time to DOM Content Loaded

The time it takes for the DOM content to load.

```python
perf.time_to_dom_content_loaded() -> float
```

### Page Weight

The amount of bytes transferred for the page to be loaded.

```python
perf.page_weight() -> float
```

### Connection Time

The time taken to connect to the server.

```python
perf.connection_time() -> float
```

### Request Time

The time taken to send a request to the server and receive the response.

```python
perf.request_time() -> float
```

### Fetch Time

The time to complete the document fetch (including accessing any caches, etc.).

```python
perf.fetch_time() -> float
```

## Examples

Store the entire <mark style="color:orange;">**WebPerformance**</mark> object in a variable, then convert it to a <mark style="color:yellow;">**Dictionary**</mark> to log it.

```python
perf = py.performance.get()
py.log.info(perf.dict())
```

Store a single data point in a variable and test against it.

```python
tti = py.performance.get().time_to_interactive()
assert tti < BASELINE, f"TTI should be less than our baseline."
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.pylenium.io/driver-commands/web-performance/performance-api.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.