Browser extensions - new tab extension
Tags: javascript, html, webdev, beginners
Published: 2022-08-13 07:35:54


We already looked at our first extension that didn't have a view and a custom theme.

Now let's look at how we can make a new tab extension.
The idea behind these is that they replace the new tab with a webpage we created.

The result will be a new tab like this:

![Browser extensions - new tab extension](https://cdn.hashnode.com/res/hashnode/image/upload/v1659508291054/h_qZLBDqZ.png)

## New tab extension setup

To get started, we first have to create a new folder and navigate into it.

```bash
mkdir new-tab-extension && cd new-tab-extension
```

Now open up the project in your favorite editor.

The first thing we will add is the `manifest.json`. This is always the main entry point for any browser extension.

```js
{
  "manifest_version": 3,
  "version": "1.0",
  "name": "New Tab Extension",
  "description": "A demo first new tab experience",
  "action": {
    "default_icon": "icons/icon-48.png"
  },
  "icons": {
    "48": "icons/icon-48.png"
  },
  "chrome_url_overrides" : {
    "newtab": "new-tab.html"
  }
}
```

We defined this one as manifest version 3 and filled out the details as required.

The main difference here lies in the `chrome_url_overrides`.
You can tell you want to override some default browser behavior.

In our example, we overwrite the `newtab` to open a file called `new-tab.html`.
This is a file we will create and make our own.

Add the `new-tab.html` file to the root of your project.
I added the following basic html structure to it.

```html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>DDT New Tab</title>
    <link rel="stylesheet" type="text/css" href="./css/style.css" />
  </head>
  <body>
    <h1>Hello world 👋</h1>
  </body>
</html>
```

You can extend this as much as you want.

As you can see, we can even link to stylesheets.
I added a new stylesheet in a `css` directory.
I do a basic reset inside the file and center the text on the page.

```css
*,
*::before,
*::after {
  box-sizing: border-box;
}
* {
  margin: 0;
}
html,
body {
  height: 100%;
}
body {
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
  display: grid;
  place-items: center;
  background-color: rgb(238 242 255);
}
p,
h1,
h2,
h3,
h4,
h5,
h6 {
  overflow-wrap: break-word;
}
h1 {
  font-size: 10vmin;
  color: rgb(218 0 96);
}
```

## Testing the extension

We don't want to publish to the stores without testing our extension, so let's see what it takes to try it locally.

I prefer to use Chrome as it has a quicker interface for it.

In Chrome, click the plugins button and open up that page.

![Chrome extension overview](https://cdn.hashnode.com/res/hashnode/image/upload/v1659333220794/C7-4tkk9O.png)

Next, toggle the developer mode on. You'll get another menu where you get the option to load unpacked extensions.

Click the load unpacked and navigate to the `new-tab-extension` folder.

Chrome will notify you that the new tab is overwritten and if you want to keep it.

You can also download this extension from [GitHub](https://github.com/rebelchris/new-tab-extension/tree/part-1) and try it out yourself.

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