# Introduction

When several people work on one WordPress site, Presence API shows who else is there: who is logged in, which screen they are on, and which posts they have open.

![The dashboard with 101 people online, the admin bar's presence menu open, and Active Posts listing who is editing each post and page.](https://raw.githubusercontent.com/WordPress/presence-api/main/plugins/presence-api/.wordpress-org/screenshot-1.png)

## What you see

- Faces in the admin bar for everyone online, and a menu saying where each person is.
- An Active Posts box on the dashboard, listing each post someone has open.
- An Editors column on the Posts screen, showing who has each post open.
- An Online view on the Users screen.
- A notice when someone else saves a screen you have open, so you do not overwrite their change.

## How it knows

```mermaid
sequenceDiagram
	accTitle: How a browser tab tells the site someone is there
	accDescr: About once a minute, each open tab tells the site which screen the person is on. The site saves a short note saying the person is there, and replies with who else is around. A note that is not renewed stops counting after 150 seconds.
	participant Tab as Your browser tab
	participant Site as Your WordPress site
	Tab->>Site: I am here, on the Dashboard
	Site->>Site: Save a note: you are on the Dashboard
	Site-->>Tab: These people are here too
	Note over Site: A note not renewed within<br/>150 seconds stops counting
```

The check-in is Heartbeat, which WordPress already sends from each open tab about once a minute. Each one renews your note, so when you close the tab you disappear from other screens within 150 seconds, without logging out.

## Words used in these docs

| Word | Meaning |
| --- | --- |
| Row | One saved note: this person is in this place, until this time |
| Room | A place people can be, such as the whole admin or one post |
| TTL | How long a row counts without being renewed, 150 seconds by default |
| Writer | Anything that saves rows, such as Heartbeat |
| Reader | Anything that shows rows, such as the admin bar |

## Try it

[Presence Scenes in Playground](https://playground.wordpress.net/?blueprint-url=https://raw.githubusercontent.com/WordPress/presence-api/main/blueprint-scenes.json) opens a WordPress site in your browser, with nothing to install, and plays two people editing one post. Watch the faces in the admin bar.

## Check your understanding

<details>
<summary>You close your laptop lid with the dashboard open. How long do others still see you online?</summary>

Up to 150 seconds. Your tab stops checking in, so your note is no longer renewed and stops counting when its time runs out.

</details>