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Fix #1630 (#1660)
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Kayce Basques authored Nov 5, 2019
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10 changes: 9 additions & 1 deletion src/site/content/en/lighthouse-performance/first-cpu-idle/index.md
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Expand Up @@ -4,11 +4,19 @@ title: First CPU Idle
description: |
Learn about Lighthouse's First CPU Idle metric and how to optimize it.
date: 2019-05-02
updated: 2019-10-10
updated: 2019-11-05
web_lighthouse:
- first-cpu-idle
---

{% Aside 'caution' %}
First CPU Idle is deprecated in Lighthouse 6.0. While some have found that First CPU Idle
offers a more meaningful measurement than [Time To Interactive](/interactive), the difference
isn't significant enough to justify maintaining two similar metrics. Moving forward,
consider using [Total Blocking Time](/lighthouse-total-blocking-time/) and
[Time To Interactive](/interactive) instead.
{% endAside %}

First CPU Idle is one of six metrics
tracked in the **Performance** section of the Lighthouse report.
Each metric captures some aspect of page load speed.
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11 changes: 10 additions & 1 deletion src/site/content/en/lighthouse-performance/first-meaningful-paint/index.md
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Expand Up @@ -5,11 +5,20 @@ description: |
Learn about Lighthouse's First Meaningful Paint metric and
how to measure and optimize it.
date: 2019-05-02
updated: 2019-10-10
updated: 2019-11-05
web_lighthouse:
- first-meaningful-paint
---

{% Aside 'caution' %}
First Meaningful Paint (FMP) is deprecated in Lighthouse 6.0. In practice FMP
has been overly sensitive to small differences in the page load, leading to inconsistent
(bimodal) results. Additionally, the metric's definition relies on browser-specific
implementation details, which means it cannot be standardized nor implemented in all web
browsers. Moving forward, consider using [Largest Contentful Paint](/largest-contentful-paint/)
instead.
{% endAside %}

First Meaningful Paint (FMP) is one of six metrics
tracked in the **Performance** section of the Lighthouse report.
Each metric captures some aspect of page load speed.
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160 changes: 144 additions & 16 deletions src/site/content/en/lighthouse-performance/performance-scoring/index.md
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@@ -1,9 +1,11 @@
---
layout: post
title: "Lighthouse performance scoring"
title: Lighthouse performance scoring
description: |
Learn how Lighthouse generates the performance score for your page.
Learn how Lighthouse generates the overall Performance score for your page.
subhead: How Lighthouse calculates your overall Performance score
date: 2019-09-19
updated: 2019-10-14
---

In general, only [metrics audits](/lighthouse-performance/#metrics)
Expand All @@ -15,9 +17,39 @@ real website performance data from the [HTTP Archive](https://httparchive.org/).
100 is the highest possible score and indicates
your page is in the ninety-eighth percentile of websites for that metric.

## Why your score fluctuates {: #fluctuations }

A lot of the variability in your overall Performance score and metric scores is not due to Lighthouse.
[Project Lantern](https://github.com/GoogleChrome/lighthouse/blob/master/docs/lantern.md) has minimized
much of the variance in Lighthouse's measurements.

When your Performance score fluctuates it's usually because of changes in underlying conditions. Common
problems include:

* A/B tests
* Internet traffic routing changes
* Testing with different versions of Lighthouse
* Testing on different devices, such as a high-performance desktop and a low-performance laptop
* Browser extensions that inject JavaScript into all pages you visit and make network requests

Furthermore, even though Lighthouse can provide you a single overall Performance score, it might be more
useful to think of your site performance as a distribution of scores, rather than a single number.
See the introduction of [User-Centric Performance Metrics](https://developers.google.com/web/fundamentals/performance/user-centric-performance-metrics)
to understand why.

## How the performance metrics are weighted {: #weightings }

Each audit is weighted based on heuristics.
More heavily weighted audits have a bigger effect on your overall Performance score.
The table below shows the weighting for each contributing performance audit.
The tables below show the weighting for each metric in each version of Lighthouse.

{% Aside %}
The weightings have changed over time because the Lighthouse team is regularly
doing research and gathering feedback to understand which metrics have the biggest
impact on user-perceived performance.
{% endAside %}

### Lighthouse 6

<div class="w-table-wrapper">
<table>
Expand All @@ -30,34 +62,130 @@ The table below shows the weighting for each contributing performance audit.
<tbody>
<tr>
<td><a href="/first-contentful-paint/">First Contentful Paint</a></td>
<td>3</td>
<td>20%</td>
</tr>
<tr>
<td><a href="/speed-index/">Speed Index</a></td>
<td>10%</td>
</tr>
<tr>
<td><a href="/first-meaningful-paint/">First Meaningful Paint</a></td>
<td>1</td>
<td>20%</td>
</tr>
<tr>
<td><a href="/interactive/">Time to Interactive</a></td>
<td>15%</td>
</tr>
<tr>
<td><a href="/lighthouse-total-blocking-time/">Total Blocking Time</a></td>
<td>20%</td>
</tr>
</tbody>
</table>
</div>


### Lighthouse 5

<div class="w-table-wrapper">
<table>
<thead>
<tr>
<th>Audit</th>
<th>Weight</th>
</tr>
</thead>
<tbody>
<tr>
<td><a href="/first-contentful-paint/">First Contentful Paint</a></td>
<td>23%</td>
</tr>
<tr>
<td><a href="/speed-index/">Speed Index</a></td>
<td>4</td>
<td>27%</td>
</tr>
<tr>
<td><a href="/first-meaningful-paint/">First Meaningful Paint</a></td>
<td>7%</td>
</tr>
<tr>
<td><a href="/interactive/">Time to Interactive</a></td>
<td>33%</td>
</tr>
<tr>
<td><a href="/first-cpu-idle/">First CPU Idle</a></td>
<td>2</td>
<td>13%</td>
</tr>
</tbody>
</table>
</div>

### Lighthouse 3 and 4

<div class="w-table-wrapper">
<table>
<thead>
<tr>
<th>Audit</th>
<th>Weight</th>
</tr>
</thead>
<tbody>
<tr>
<td><a href="/first-contentful-paint/">First Contentful Paint</a></td>
<td>23%</td>
</tr>
<tr>
<td><a href="/speed-index/">Speed Index</a></td>
<td>27%</td>
</tr>
<tr>
<td><a href="/first-meaningful-paint/">First Meaningful Paint</a></td>
<td>7%</td>
</tr>
<tr>
<td><a href="/interactive/">Time to Interactive</a></td>
<td>5</td>
<td>33%</td>
</tr>
<tr>
<td><a href="/first-cpu-idle/">First CPU Idle</a></td>
<td>13%</td>
</tr>
</tbody>
</table>
</div>

{% Aside %}
Your Performance score will vary somewhat each time you run Lighthouse because
of changes in underlying conditions (for example, network speed).
You can minimize variations by running Lighthouse without any programs
that affect page load, like anti-virus scanners or browser extensions.
{% endAside %}
### Lighthouse 2

See the [Lighthouse Scoring Guide](https://developers.google.com/web/tools/lighthouse/v3/scoring#a11y)
for more information.
<div class="w-table-wrapper">
<table>
<thead>
<tr>
<th>Audit</th>
<th>Weight</th>
</tr>
</thead>
<tbody>
<tr>
<td><a href="/first-contentful-paint/">First Contentful Paint</a></td>
<td>6%</td>
</tr>
<tr>
<td><a href="/speed-index/">Speed Index</a></td>
<td>6%</td>
</tr>
<tr>
<td><a href="/first-meaningful-paint/">First Meaningful Paint</a></td>
<td>29%</td>
</tr>
<tr>
<td><a href="/interactive/">Time to Interactive</a></td>
<td>29%</td>
</tr>
<tr>
<td><a href="/first-cpu-idle/">First CPU Idle</a></td>
<td>29%</td>
</tr>
</tbody>
</table>
</div>

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