Custom Close integration development
Appfront builds custom Close integrations that connect your sales CRM to your website, marketing stack or own application. Using the Close REST API and webhooks, we synchronise leads, contacts, opportunities and activities in real time. Your team works in a single pipeline, website leads land straight in Close, and your other systems stay automatically up to date.
What is a Close integration?
Close is a sales CRM for B2B teams, SaaS companies and start-ups, bringing calling, email and SMS together in one tidy pipeline. The model revolves around leads: a company or organisation that holds contacts, tasks, opportunities and activities. Where many CRMs become heavy and cumbersome, Close is built for speed: calling, emailing and following up from the same view.
In practice, a custom integration means: automatically creating leads and contacts from your website forms, synchronising opportunities and pipeline status with your own systems, reading activities such as calls and emails for reporting, populating custom fields with data from your application, and reacting in real time via webhooks whenever something changes in Close.
Appfront builds according to the official Close developer documentation and the OWASP ASVS security standard. We tailor the data model, synchronisation direction and error handling to your actual sales process, so the integration grows with your team and stays reliable at high volumes.
Leads and contacts in sync
Website leads, form submissions and contacts land automatically in the right Close lead, with no duplicate entry. Updates flow both ways: if a contact changes in your system, Close follows, and vice versa.
Pipeline insight
Opportunities and their status (active, won or lost) flow into your dashboards and reporting. Management sees pipeline value in real time, without manually exporting from Close.
Real-time via webhooks
As soon as an opportunity is won or a lead status changes, Close sends a webhook. Your onboarding, invoicing or email flow starts straight away, with no polling and no delay.
Our development process for Close integrations
We work to a proven methodology that removes uncertainty early and delivers a stable integration. From an initial analysis of your sales process and the data flows you need, through to go-live and ongoing management, every step is aimed at an integration your team can understand and trust.
We map out which objects you want to integrate (leads, contacts, opportunities or activities), in which direction the data should flow, and which custom fields and triggers are involved.
We design the integration architecture, choose between API key and OAuth 2.0, and set up an error handling and retry strategy.
Implementation with automated tests, structured logging and monitoring. You see working builds along the way.
Controlled go-live with data validation and a safety net, followed by ongoing management and further development.
What a Close integration delivers in practice
Every Close integration is set up specifically for your sales process, data flows and adjacent systems. Below are the capabilities we most often deliver for organisations that run Close at the heart of their commercial process.
REST API and secure authentication
We build on the official Close REST API using JSON over predictable endpoints. Authentication runs via an API key (HTTP Basic) for server-side integrations, or via OAuth 2.0 for user-facing integrations, always with scoped permissions and keys held in a secure vault.
Lead and contact sync
We synchronise leads (companies or organisations) and their underlying contacts, including multiple phone numbers, email addresses and URLs, between Close and your website, marketing tool or application. With deduplication, so the same prospect does not end up in the pipeline twice.
Opportunities & pipeline
We connect opportunities, with their status (active, won or lost) and optionally an amount, to your dashboards, invoicing or forecasting. Status changes flow in both directions, so the pipeline in Close and your own system always stay in step.
Activities: calls and emails
We read activities in Close (calls, emails, email threads, SMS, WhatsApp, meetings and notes) for reporting, or write them from your systems. This keeps the full contact history with a lead in one place.
Webhooks and event log
With webhooks, your system receives a POST whenever something changes in Close: a new lead, a won opportunity, a completed call. We validate the signature and capture events reliably; the event log, with 30 days of history, acts as a safety net for missed notifications.
Custom fields and segments
We connect your own fields and segments via Close's custom field structure. Data from your application populates the right fields on leads and contacts, so smart views and filters in Close are accurate and your sales team can act straight away on the right segments.
Typical use cases in practice
A Close integration looks very different from one organisation to the next. We see a number of recurring patterns, and for each we have a working setup with attention to the data model, synchronisation direction and the right webhook triggers.
B2B sales teams
B2B teams selling by phone and email from Close. Website leads land directly in the pipeline, opportunities and their status synchronise with your dashboards, and won deals automatically trigger your onboarding. See also our API integrations.
SaaS & startups
SaaS companies and start-ups that want to scale quickly with a lean, fast sales motion. Sign-ups from the product flow into Close as leads, trial behaviour enriches the opportunity, and webhooks connect Close to invoicing and customer success. Our web app development service also fits in with this.
Inside sales
Inside sales teams handling high volumes of calls and emails from a single pipeline. We integrate lead sources, feed calls and emails back as activities for reporting, and automate follow-up via webhooks so no lead falls through the cracks.
Agencies & professional services
Agencies and professional service providers with their own sales motion who use Close for new business. Enquiry forms on the website create a lead straight away, contacts and opportunities sync with your project tool, and a won deal kicks off your bespoke intake workflow.
Technology we use
We build Close integrations using the official REST API and webhooks, combined with the backend stack that suits you. The exact choice depends on your existing systems and the synchronisation direction you need, so your own team can manage or further develop the implementation.
Why choose Appfront for your Close integration?
Appfront has extensive experience building API integrations for a wide range of organisations in the Netherlands. We always start with a thorough analysis of your existing systems and processes. An integration should not only work technically, but also add practical value to the way you work.
For every integration, we write clear documentation and make sure your own team, or any future supplier, can understand and manage it. No black box, just transparent code and clear agreements on monitoring, alerting and maintenance.
You work with a dedicated point of contact who understands both the technical and the functional side. This keeps communication short, prevents misunderstandings and speeds up decisions when choices need to be made during development.
See also our wider services around API integrations, middleware, custom software development and web app development.
- Experience with the Close REST API, webhooks and the lead/opportunity model
- Specialists in CRM integrations for B2B sales teams and SaaS
- Well versed in custom fields, activity sync and pipeline automation
- Secure by default: API key rotation, webhook signature validation, scoped permissions
- Structured error handling and retry mechanisms
- Comprehensive logging and monitoring from day one
- Clear documentation your team can read and manage
- A fixed point of contact, no account managers passed around
- Ongoing maintenance and proactive further development
- A way of working aligned with your existing IT landscape
Security and privacy in Close integrations
By definition, a CRM holds personal data about leads, contacts and customers: names, phone numbers, email addresses and the full contact history. Appfront builds in line with the OWASP ASVS. This means, among other things: API keys held in secure vaults, webhook signature validation, scoped OAuth permissions and regular audits of the data flows between Close and your systems.
We follow data minimisation: only the fields the integration needs are synchronised, and tokens are issued with the narrowest possible scope. We document the data flows between Close and your application so your record of processing activities is complete and you can demonstrate compliance with the GDPR. We rotate API keys periodically and keep them strictly separated per integration.
More on our security approach: information security policy and CVD policy.
- GDPR-compliant data processing and data minimisation
- Encryption in transit (TLS 1.2+) and at rest
- Role-based access and least-privilege principles
- Audit logs with traceable data flows
- Automatic retries and dead-letter queues
- Monitoring and alerting for anomalies
- Secrets management in line with best practice
- Documentation for your record of processing activities
Frequently asked questions about Close integrations
Answers to the questions we are asked most often about Close integrations.
A Close integration is a technical link between Close.com and another system, such as your website, marketing stack, invoicing tool or own application. Through the Close REST API, leads, contacts, opportunities and activities are created and synchronised programmatically. Webhooks push real-time updates whenever something changes in Close. An integration can be simple (a website form that creates a lead in Close) or extensive (two-way sync of pipeline, custom fields and activities).
Close is a good fit for B2B sales teams, SaaS companies, start-ups and inside-sales organisations that make a lot of calls and send many emails from a single CRM. Close includes built-in calling, email and SMS, and a streamlined pipeline designed for speed. For teams looking to automate outbound and follow-up workflows, it is a strong option. If you need heavy enterprise functionality or marketing automation, we will work out together whether Close or another platform is a better match.
The Close REST API lets you connect, among other things, leads, contacts, opportunities, activities (calls, emails, SMS, notes and meetings), tasks, custom fields and smart views. Common integrations include website forms that create leads, a data warehouse that reads pipeline data, a marketing tool that synchronises contacts, and webhooks that keep your own system informed of status changes. We tailor the scope to your actual sales process.
We work with the official Close REST API and webhooks, combined with the backend stack that suits you: Node.js, Python, PHP, .NET, Ruby or Go. Authentication runs via an API key (HTTP Basic) for server-side integrations, or via OAuth 2.0 for user-facing integrations. For data modelling we use the lead, contact, opportunity and activity resources, with custom fields where your process requires them.
The cost is determined by the complexity of the data flows, the number of systems to connect, the desired direction and frequency of synchronisation, and the amount of custom business logic. Ongoing maintenance, monitoring and support also affect the total investment. We always provide a clear quote following a no-obligation analysis of your situation.
Yes. A CRM inherently holds personal data about leads and customers, so we handle that data with care. Appfront builds to the OWASP ASVS standard: API keys are kept in secure vaults, webhook signatures are validated, tokens are scoped with minimal permissions, and permissions are separated per integration. We document the data flows between Close and your systems so that your record of processing activities remains complete and you can demonstrably comply with the GDPR.
Yes. Appfront regularly takes over existing CRM integrations, even if they were originally set up by another party. We review the API integration, webhook configuration, custom field model and error handling, document the current setup and propose improvements. From that point on, we handle adjustments, extensions and monitoring, including timely rotation of API keys.
Close suits B2B sales teams that sell by phone and email: SaaS companies, startups, inside sales departments, scale-ups, and agencies or service providers with their own sales motion. Typical integrations include website leads landing directly in the pipeline, marketing contacts syncing in both directions, pipeline data flowing into a dashboard, and webhooks that trigger your onboarding or invoicing as soon as an opportunity is won.
Ready to build your Close integration?
Tell us which leads, contacts or opportunities you want to synchronise, and which systems Close needs to connect with. We're happy to help you think through the data model, the sync direction and the right webhook triggers. A no-obligation first conversation gives you a clear picture of what's possible within half an hour. You can also take a look at our integrations.