Build a Link Preview integration

A Link Preview is a real-time excerpt of authenticated content that unfurls in Notion when an authenticated user pastes a supported link in their workspace.

Developers can build Link Preview integrations to customize how links unfurl in Notion workspaces for domains they own.

This guide explains how to use the Notion Link Previews API to create Link Previews for your product. After you’ve read this guide, you’ll know how to:

1. Configure Link Preview settings in the integration dashboard

2. Set up the authorization flow

3. Use the Unfurl Callback URL

4. Manage updates to Link Previews

5. Submit a Link Preview integration for security review

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To build a Link Preview integration, you must first request access to the Link Preview API. Fill out the Link Preview request form before proceeding if you haven’t already.

Requirements

• You’ve requested and received access to the Link Previews API.
• You own the domain that you’re using to create Link Previews. You’ll need to share a verification code from Notion with your domain host when you initialize the integration.
• Your application supports OAuth 2.0.
• You’ve read the Link Previews overview, so you have a good idea of what you’re building and how it works.
• You’ve read the Authorization guide and have familiarized yourself with Notion integrations.
• The Link Preview destination is not gated and is generally available to all your users

With those requirements met, read on!

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To build a Link Preview integration, you must first request access to the Link Preview API. Fill out the Link Preview request form before proceeding if you haven’t already.

🌱 Create a public Notion integration

Link Preview integrations are a type of public integration. To create a Link Preview integration, you must first create a public integration. Once the public integration is created, you can enable the link preview setting through the integration's settings.

To learn how to create a public integration, follow the Authorization guide.

In short, you will need to:

1. Create a new integration in the integrations dashboard. All integrations are “internal” to start.
2. Convert the integration to be a public integration.

Now that the integration is public and you have already been given access to the Link Previews API, you are ready to build a Link Preview integration.

🛠️ Configure Link Preview settings in the integration dashboard

This step will guide you through enabling link previews for your integration, as well as filling out the link preview integration forms found in your integration settings.

To start, navigate to the public integration you will be using for your link preview integration. It can be found in the integration dashboard. If you have access to the Link Preview API, you will see a Link Preview tab in the side navigation.

This page contains a toggle input to enable link previews for your integration. Switching it on will display the External Authorization Setup form that will you need to fill out and save.

Once the link preview toggle is turned on for the integration, you will need to fill out two forms in the following order:

1. The External Authorization Setup form.
2. The Unfurling Domain & Patterns form.

In the next section, we'll review how to fill out these forms.

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If you don't see Link preview as an option, then:

• Make sure that you’ve applied and received access to the Link Previews API.
• Confirm that you’re logged in to the Notion account that you used to request access.
• Reach out to [email protected] if you continue to have issues.

1. Fill out the External Authorization Setup form

The External Authorization Setup settings give Notion the information that it needs to let a user authenticate with your service when they paste a Link Preview enabled URL in Notion.

After you’ve filled out this information, click "Submit ->" to continue to Unfurling Domain & Patterns.

2. Fill out the Unfurling Domain & Patterns form

The Unfurling Domain & Patterns settings give Notion the information that it needs to recognize the URLs that you want to unfurl Link Previews.

The URL matching and placeholder field includes its own fields:

After you've filled out the External Authorization Setup and Unfurling Domain & Patterns settings, click "Submit ->" to create the integration.

🔒 Set up the authorization flow

There are two high-level parts to the auth flow for a Link Preview:

• Your service authenticates with Notion. Notion sends a code to your OAuth Authorize URL. Your integration exchanges this code for a Notion access_token that enables your service to make authenticated requests to the Link Previews APIs.
• Notion authenticates with your service. Your service responds to Notion’s request with a code. Notion exchanges this token for your service’s access_token via your OAuth Token URL. This allows Notion to embed the data from your service in Link Previews.

The tokens need to be exchanged the first time a user attempts to add your Link Preview enabled URL to a page. After the initial exchange, the Notion access_token is long-living and doesn’t need to be updated. If you prefer, Notion can also support refresh tokens and fetch new tokens from your service.

The auth flow begins when a user shares your Link Preview enabled URL in Notion. Notion recognizes the link and redirects to the OAuth Authorize URL that you provided in the integration settings.

Notion includes the following query params to kick off the OAuth flow with your service:

Your implementation begins after Notion sends the request.

1. Provide OAuth form

Listen for requests to your OAuth Authorize URL. When you detect a request from Notion, present a UI that asks the user to allow the authentication process to continue.

For example, Slack shares the following interstitial when a user initiates a Link Preview from a Slack URL:

2. Authenticate with Notion’s access_token

In your integration implementation, retrieve the code that Notion sent when it called your OAuth Authorize URL. Then, send the code as part of a POST request to Notion’s token URL: https://api.notion.com/v1/oauth/token.

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The Notion code is valid for 10 minutes. If the code expires, then an error is returned and you need to reinitiate the auth flow for Notion to authenticate with your service (Step 2a).

To explore other possible errors, refer to the OAuth 2.0 documentation. Default to re-initiating the auth flow to handle errors.

The request is authorized using HTTP Basic Authentication. The credential is a colon-delimited combination of the integration’s CLIENT_ID and CLIENT_SECRET: CLIENT_ID:CLIENT_SECRET. You can find these values on the integration settings page. Visit notion.so/my-integrations, find your integration, and click View integration.

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Note that in HTTP Basic Authentication, credentials are base64 encoded before being added to the Authorization header. Notion also requires the word Basic before the base64 encoded string. A complete code param looks something like the following:

Basic NjQ5Mzc0OTIzNzQ5MjM4NDc5MjM4NDc5MjM0NzkyMzc0OjQ3Mzg5Mjc0OTIzODQ3Mjk0ODcyMzkzNDgyNzk0ODcyMzQ5

For more information, read about HTTP Basic Authentication in our Authorization guide.

The body of the request contains the following JSON-encoded fields:

The following example demonstrates an external_account object for [email protected], a Notion employee account, to authenticate with Slack to use a Slack Link Preview.

{
  "key": "A83823453409384",
  "name": "Notion - [email protected]"
}

The account name appears in the "My connections" settings page, where a user can review their authentications for your integration.

A complete POST request looks like the below:

curl --location --request POST 'https://api.notion.com/v1/oauth/token' \
--header 'Authorization: Basic '"$BASE64_ENCODED_ID_AND_SECRET"'' \
--header 'Content-Type: application/json' \
--header 'Notion-Version: 2022-06-28' \
--data '{
  "grant_type": "authorization_code",
  "code": "e202e8c9-0990-40af-855f-ff8f872b1ec6",
	"external_account": {
		"key": "A83823453409384",
		"name": "Notion - [email protected]"
	}
}'

Notion responds to the request with a 200 OK and the following response body:

Store the Notion response, and associate it with the user who initiated the OAuth flow. Notion stores the token that you provided.

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For tips on storing access_tokens, check out the auth guide.

3. Redirect to the redirect_uri with code

When a user selects "Allow" to grant Notion the requested permissions, redirect to the redirect_uri , the constant string notion.so/externalIntegrationAuthCallback, with your service’s unique code and the state that Notion sent to your service when it initiated the auth flow.

When Notion receives the redirect, it sends a POST request to the OAuth Token URL that you provided with the following body:

The body is sent in the application/x-www-form-urlencoded format and expects a JSON response.

4. Share the access_token with Notion

From your OAuth Token URL, respond to Notion’s POST request with an access_token body parameter in your 200 response.

Notion saves the access_token to send in future requests. Notion sends a request to your Unfurl Callback URL every time that the user associated with the token pastes a new Link Preview enabled URL or revisits a page with an existing Link Preview to refresh data.

How Notion handles OAuth errors

Notion handles error responses as described by the OAuth Error Spec. The message that Notion displays to the user varies depending on the information that you provide.

For example, you can respond with an error and a standard error code like access_denied:

https://notion.so/externalintegrationauthcallback?error=access_denied

In this instance, Notion shares the following message:

You can also add an error_description to the response:

https://notion.so/externalintegrationauthcallback?error=access_denied&error_description=The+user+has+denied+your+application+access

If Notion detects a description, then it replaces the standard dialogue prompt with the specified description, as in the below:

If Notion doesn’t recognize the error code, then it notes that the error is unknown:

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For more details on standard error codes, refer to the OAuth spec.

How to use refresh tokens (optional)

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Skip to Step 2e if you’re creating long-living access tokens. This section only applies to temporary access tokens.

Return a refresh_token

Instead of creating a long-living access_token, you can send a refresh_token alongside a temporary access token. Notion can then use the refresh_token to fetch new tokens from your service.

If you return a refresh_token, then you need to also return an expires_in integer, as in the following example:

{
  "access_token": "ABC",
  "refresh_token": "XYZ",
  "expires_in": 60000
}

expires_in represents the number of seconds until the access_token expires.

Notion requests to refresh a token

If Notion detects that the access_token is expired, meaning that the current time exceeds the time of the last refresh plus the expires_in value, then Notion refreshes the tokens when it calls your endpoints.

To refresh the token, Notion sends a POST request to your OAuth Token URL with the following parameters:

Respond to Notion’s request to refresh a token

From your OAuth Token URL, return an access_token in your 200 response. You can optionally return new refresh_token and expires_in values.

5. Test the auth flow in Notion

To test the auth flow, make sure that you’ve added the integration to a workspace. Then, navigate to "My connections" in the workspace settings. Click "Show all". Find the integration that you created in the list, and select "Connect" to kick off the auth flow.

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If you don’t see your integration in the list, then refresh the page. Notion only loads new integrations on page load.

If the auth flow is successful, then you’ll see a new entry under the "My connections" menu.

To verify that the key for this connection is unique, repeat the auth flow multiple times using the same credentials to validate that you only get a single entry.

📞 Use the Unfurl Callback URL

1. Configure unfurl attributes

After a user pastes a Link Preview enabled link and completes the auth flow, Notion sends a POST request to the Unfurl Callback URL that you provided in the integration settings.

The request includes a Bearer authorization with the user’s access_token from your service, and the payload is a single field called uri that includes the link that the user shared:

curl -d '{"uri":"http://example.com/file/123"}' \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer <ACCESS_TOKEN>"
    -X POST https://example.com/unfurl

Set up the Unfurl Callback URL to respond to Notion’s request with a 200 OK including the uri, and an array of all of the unfurl attributes, the values to display in the Link Preview. The array must include a title attribute that gives the Link Preview a title and a dev attribute that indicates the developer or company that created the Link Preview.

The following is an example response:

{
  "uri": "http://example.com/file/123",
  "operations": [
    {
      "path": [
        "attributes"
      ],
      "set": [
        {
          "id": "title",
          "name": "Title",
          "type": "inline",
          "inline": {
            "title": {
              "value": "The Link Preview's Title",
              "section": "title"
            }
          }
        },
        {
          "id": "dev",
          "name": "Developer Name",
          "type": "inline",
          "inline": {
            "plain_text": {
              "value": "Acme Inc",
              "section": "secondary"
            }
          }
        },
        {
          "id": "color",
          "name": "Color",
          "type": "inline",
          "inline": {
            "color": {
              "value": {
                "r": 235,
                "g": 64,
                "b": 52
              },
              "section": "background"
            }
          }
        }
      ]
    }
  ]
}

To preview how different response objects unfurl in a Link Preview, explore the integration's Link Preview Lab.

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To learn more about unfurl attributes, refer to the Link Preview unfurl attributes reference.

2. Handle unfurl request errors

Set up the Unfurl Callback URL to handle errors, as in the following example.

{
  "uri": "http://example.com/file/123",
    "operations": [
        {
          "path": ["error"],
	        "set": { "status": 404, "message": "Content not found" }
        }
}

🔁 Manage updates to Link Previews

Update Link Previews to reflect data shared in unfurl attributes

If the unfurl attributes from your service change over time, then you can alert Notion to update the Link Preview to mirror those changes.

When your service detects changes to data that is referenced by a Link Preview, send a PATCH request to Notion’s /v1/external/object endpoint to update the unfurl attributes.

Include all of the same objects from the Unfurl Callback URL response in the request, including the attributes that haven’t changed, as in the following example:

curl -d `{
  "uri": "http://example.com/file/123",
    "operations": [
        {
          "path": ["attributes"],
        "set": [
          {
            "id": "title",
            "name": "Title",
            "type": "inline",
            "inline": {
              "title": {
                "value": "The Link Preview's NEW Title",
                "section": "title"
              }
            }
          },
          {
            "id": "color",
            "name": "Color",
            "type": "inline",
            "inline": {
              "color": {
                "value": {
                  "r": 235,
                  "g": 64,
                  "b": 52
                },
                "section": "background"
              }
            }
          }
        ]
        }
  ]
}` \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer <ACCESS_TOKEN>" \
	  -H "Notion-Version: 2021-08-16" \
    -X PATCH https://api.notion.com/v1/external/object

It’s also possible to set a new error request. For example, if the data originally shared in a Link Preview can’t be found, then you could send an update request as follows:

curl -d `{
  "uri": "http://example.com/file/123",
    "operations": [
        {
          "path": ["error"],
	        "set": { "status": 404, "message": "Content not found" }
        }
  ]
}` \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer <ACCESS_TOKEN>" \
	  -H "Notion-Version: 2021-08-16" \
    -X PATCH https://api.notion.com/v1/external/object

You can also set both new attributes and an error request at the same time, as in the below example:

curl -d `{
  "uri": "http://example.com/file/123",
    "operations": [
        {
          "path": ["attributes"],
	        "set": [
	          {
	            "id": "title",
	            "name": "Title",
	            "type": "inline",
	            "inline": {
	              "title": {
	                "value": "The Link Preview's Title",
	                "section": "title"
	              }
	            }
	          },
	          {
	            "id": "color",
	            "name": "Color",
	            "type": "inline",
	            "inline": {
	              "color": {
	                "value": {
	                  "r": 235,
	                  "g": 64,
	                  "b": 52
	                },
	                "section": "background"
	              }
	            }
	          }
	        ]
        },
        {
          "path": ["error"],
	        "set": { "status": 404, "message": "Content not found" }
        }
  ]
}` \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer <ACCESS_TOKEN>" \
	  -H "Notion-Version: 2021-08-16" \
    -X PATCH https://api.notion.com/v1/external/object

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When updating a Link Preview’s unfurl attributes, there’s no need to clear the error. If no error is sent, then the error is automatically cleared.

Notion updates your service when a user deletes Link Preview enabled URLs

When a user deletes all Link Previews associated with a URL from their workspace, Notion sends a DELETE request to your Unfurl Callback URL.

Listen for the request to perform any associated actions, like deleting the record from your service.

💫 Submit your integration for security review

Before a Link Preview integration can be publicly distributed, it needs to pass a security review. Fill out this form to submit your integration for review.

👀 Next steps

• To learn more about customizing a Link Preview’s unfurl attributes, refer to the reference docs