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# Source leads

> How to read and write leads and contacts to keep customer CRMs in sync using the Merge CRM API.

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#### User authorizes access

Your user authorizes your application to access their CRM (e.g. Salesforce, Hubspot) via an OAuth or similar authorization flow through Merge Link.

#### Fetch leads

Utilize the [**GET** /leads](https://docs.merge.dev/crm/leads/#leads_list) endpoint to fetch existing leads from your customer's CRM.

#### Fetch contacts

Utilize the [**GET** /contacts](https://docs.merge.dev/crm/contacts/#contacts_list) endpoint to fetch existing contacts from your customer's CRM.

> **Note**
>
> If there are any custom CRM fields that need to be pulled in, you can use [Remote Fields](/merge-unified/supplemental-data/remote-field-classes/remote-field-classes).

#### Create contacts and leads

As new contacts and leads get sourced, push them to your customers' CRMs using the [**POST** /contacts](https://docs.merge.dev/crm/contacts/#contacts_create) and [**POST** /leads](https://docs.merge.dev/crm/leads/#leads_create) endpoints.

#### Refresh contact and lead data regularly

Regularly call the [**GET** /contacts](https://docs.merge.dev/crm/contacts/#contacts_list) and [**GET** /leads](https://docs.merge.dev/crm/leads/#leads_list) endpoints using the `modified_after` query parameter to track updates to contacts and leads. Now your customers' contacts and leads in their CRM are always up-to-date!

> **Note**
>
> Use [webhooks](/merge-unified/reading-data/webhooks/merge-webhooks) for efficient and real-time syncs.

#### Start sourcing leads with Merge

Integrate today or talk to our sales team to learn how Merge unlocks hundreds of integrations in days - not years.

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Get a demo **

* [Remote Fields](/merge-unified/supplemental-data/remote-field-classes/remote-field-classes)

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