n-Keap Has a Real API. Most Accounts Never Call It Directly.
Keap runs a REST API secured with OAuth 2.0, covering contacts, companies, tags, custom fields, orders, and pipeline opportunities, with developer docs and an app marketplace sitting on top of it. If your account traces back to the old Infusionsoft days, you may have run into an older API style too. Both versions exist so a business can read from or write to Keap programmatically, but turning that into a reliable integration is still real development work, not a weekend script.
What the Keap API actually covers
The current REST API lets you create, read, and update contacts and companies, apply or remove tags, set custom field values, pull and create orders, and work with pipeline opportunities and their stages. Authentication runs through OAuth 2.0, so an integration has to request specific scopes and get a user's approval rather than getting blanket access to the account.
Webhooks are part of the picture too: you can subscribe to events like a contact being added, a tag getting applied, or an order being placed, and have Keap push that event to your system the moment it happens instead of polling the API on a timer and hoping nothing slipped through.
If your Keap account has been around since its Infusionsoft days, some of what you'll find in older developer forums and documentation still refers to the earlier API style that account was originally built against. We check which API generation an account is actually running on before building anything, rather than assuming every Keap account looks the same underneath.
Where most businesses stop and hire this out
Making one successful test call against Keap's API is genuinely quick. Building something that keeps running correctly through token refreshes, handles a webhook delivery that fails silently, and doesn't quietly drop a tag update when two automations fire at once is a different scope of work. That gap is exactly why keap integrations and infusionsoft developer show up as real searches alongside the raw API documentation query.
The custom field piece trips people up most often. Keap lets you build a long list of custom fields on a contact record, but using those fields in an external system means the API call has to reference the right internal field ID, not just the label you see on screen. Get that wrong and the integration looks like it's working until the data lands in the wrong place.
What We Build Against Keap's API
Custom field data that actually leaves Keap
We map a contact's custom fields to the right system of record outside Keap, an accounting tool, a project system, a membership platform, so the data you built those fields to capture gets used somewhere besides the Keap screen.
Webhook-driven automation instead of scheduled checks
We wire Keap's webhooks into the rest of your stack so a new order, a tag change, or a pipeline move triggers the next step immediately, rather than waiting on a nightly sync job to notice.
Not sure if something you want can even be built against Keap's API?
Describe what you're trying to move in or out of Keap, and we'll tell you honestly whether the current API covers it, whether it needs the older API style, or whether it needs a different approach entirely.
Thinking about building directly against Keap's API?
Tell us what's supposed to move in or out of Keap and on what trigger, and we'll scope it honestly before any code gets written. Keap's API happens to be the one in front of you right now, but the same custom-build approach applies to any system in your business that still isn't talking to the others.
Let's talk