GoHighLevel API Integration: A Practical Guide for Agencies

GoHighLevel API integration lets an outside system read and write HighLevel data directly: contacts, opportunities, calendars, conversations and more. The current API lives on the services.leadconnectorhq.com host, and you authenticate with either an OAuth 2.0 app or a private integration token. In practice, most agencies combine the API with webhooks: HighLevel pushes events out through webhook actions, and Make, n8n or your own code calls the API to fetch details and write changes back.

I build HighLevel integrations for agencies regularly. This guide covers how authentication works, the operations you will use most, how to connect the GHL API to Make.com and n8n, and the mistakes that cause broken syncs.

What the GoHighLevel API can do

The API covers most of what you can do in the HighLevel interface. Common resources include:

• Contacts: search, create, update, add and remove tags, manage custom fields.
• Opportunities: create, update stage and status, search by pipeline.
• Calendars and appointments: check free slots, create and update appointments.
• Conversations and messages: read conversations and send messages.
• Locations (sub-accounts): read location details, and at agency level, work across locations.
• Custom fields and values: read and manage the custom data clients rely on.

The exact list of endpoints, scopes and versions is in the HighLevel developer documentation. Always check it before building, because endpoints and required scopes change between API versions.

Authentication: OAuth vs private integration tokens

HighLevel's docs list two ways to authenticate.

Private integration token

A private integration token is created inside the agency or sub-account settings and scoped to the permissions you choose. It is the simplest option when you are building for your own agency or a specific client. Treat it like a password: store it in your automation tool's credential store, never in a shared document, and rotate it when staff leave.

OAuth 2.0 app

An OAuth app is created in the HighLevel marketplace developer area. Clients or sub-accounts install it and grant scopes, and your app gets access and refresh tokens. This is the right choice when you are building something many agencies or many sub-accounts will install, or when you want a cleaner permission model across clients. It is more work: you need to handle token refresh and store tokens per location.

For most agency builds I start with private integration tokens and only move to OAuth when the integration needs to be installed across many accounts.

GoHighLevel API webhook pattern

The API is pull. Webhooks are push. A reliable integration usually uses both:

1. An event happens in HighLevel, like a form submission or a pipeline stage change.
2. A workflow action sends a webhook with the contact ID, location ID and the key fields to Make, n8n or your server. See my GoHighLevel webhooks guide.
3. The receiver calls the API with the contact or opportunity ID to fetch the full, current record.
4. The receiver does the work: enrich data, post to Slack, create a ClickUp task, update a sheet.
5. The receiver writes back to HighLevel through the API, such as adding a tag or moving the opportunity.

Sending IDs in the webhook and fetching the full record from the API avoids stale data and keeps webhook payloads small.

Connecting the GHL API to Make.com

Make has a HighLevel app with ready-made modules for common operations. For anything those modules do not cover, use Make's HTTP module to call the API directly.

A typical setup:

1. Trigger: a Custom Webhook module in Make receives the event from a HighLevel workflow.
2. Fetch: a HighLevel module, or an HTTP request with your token in the Authorization header, gets the contact by ID.
3. Route: a Router splits the flow based on, for example, the pipeline or a tag.
4. Act: Slack, ClickUp and Google Sheets modules do the work.
5. Write back: an HTTP request updates the contact or opportunity.
6. Handle errors: error handlers on the HTTP modules, with a Slack alert on failure.

When calling the API with HTTP, include the headers the docs require, which include the bearer token and an API version header, and send JSON bodies. Copy header names exactly from the documentation for the endpoint you are using.

Connecting the GHL API to n8n

In n8n the same pattern applies:

1. A Webhook node receives the HighLevel event.
2. The HighLevel node handles common operations, or an HTTP Request node calls any endpoint using a stored credential.
3. IF and Switch nodes route the flow.
4. Slack, ClickUp and Google Sheets nodes do the work.
5. An error workflow posts failures to Slack.

If you are deciding which tool should own the logic, see GoHighLevel vs n8n.

Example integrations agencies build

• Lead source sync. Leads from a partner site or marketplace come in through the API, are deduplicated against existing contacts and dropped into the right pipeline.
• Won deal to onboarding. When an opportunity is won, the integration creates a ClickUp project, a Google Drive folder and a Slack channel. My client onboarding build replaced about 40 manual setup steps per new client with one form submission.
• Cross-client reporting. A scheduled scenario loops through each client location, pulls opportunity counts and values, and writes a summary to a sheet or Slack.
• Positive reply routing. When a cold email reply is classified as positive, the contact is created or updated in HighLevel and the team is pinged. I run a positive-reply sales alert built on this pattern.
• Data enrichment. New contacts are enriched with company data before the sales team sees them. See data enrichment pipelines.

Common GoHighLevel API mistakes

• Wrong location context. Many calls are scoped to a location. Using an agency-level token against a sub-account endpoint, or the wrong location ID, returns errors or empty results.
• Missing scopes. A token without the needed scope fails with an authorization error. Check scopes when you create the token.
• Creating duplicates. Always search by email or phone before creating a contact, or use an upsert-style operation where the docs offer one.
• Ignoring rate limits. Loops across many contacts can hit limits. Add delays or batch the work, and check the current limits in the docs.
• Hard-coded custom field IDs. Custom field IDs differ between sub-accounts, even from the same snapshot in some cases. Look them up per location.
• No logging. When a sync fails, you need to know which record and why. Log failures to a sheet or Slack.

How I build this

I build GoHighLevel API integrations with Make, n8n and custom code, connected to Slack, ClickUp, Google Workspace and whatever else your agency runs on. See my API integrations service, or if you already have an integration that breaks, the Automation Rescue is a 48-hour fixed-price fix. For a quick review first, request a free 15-minute Loom teardown.

FAQ

Does GoHighLevel have an API?

Yes. HighLevel has a documented API for contacts, opportunities, calendars, conversations and more, authenticated with OAuth 2.0 or a private integration token.

How do I get a GoHighLevel API key?

For your own agency or a client account, create a private integration token in the settings and choose its scopes. For an app many accounts will install, create an OAuth app in the HighLevel developer marketplace.

Can I use the GoHighLevel API with Make.com?

Yes. Make has a HighLevel app for common actions, and the HTTP module can call any endpoint in the API with your token.

What is the difference between the GoHighLevel API and webhooks?

Webhooks push events out of HighLevel when something happens. The API lets an outside system request or change data whenever it needs to. Most integrations use both.