TL;DR
API (Application Programming Interface) is a way for different systems to communicate. API integrations allow you to connect your app with payments, CRM, email marketing and other services. Here's how they work and which to choose.
Who this is for
- Developers implementing API integrations
- Business owners planning integrations in their app
- Companies looking for the best API solutions
Keyword (SEO)
api integrations, how apis work, popular apis, payment api, crm api, webhook
What is API?
API (Application Programming Interface) is an interface that allows different applications to communicate with each other. With API you can:
- Connect systems – your app can use functions of other systems
- Automate processes – e.g. automatic email sending after order
- Extend functionality – add payments, CRM, analytics without building from scratch
- Save time – you don't have to build everything yourself
How do API integrations work?
1. Authorization
Most APIs require authorization:
- API Key – simple key for authorization
- OAuth 2.0 – secure authorization with tokens
- JWT – JSON Web Token tokens
2. Request/Response
Communication via HTTP:
- GET – fetching data
- POST – sending data
- PUT/PATCH – updating data
- DELETE – deleting data
3. Webhook
Webhook is a notification from API to your app:
- Event-driven – API sends notification when something happens
- Real-time – immediate notifications
- Automation – e.g. webhook after payment triggers email sending
Popular API integrations
1. Payments
Stripe:
- Card payments, Apple Pay, Google Pay
- Subscriptions and recurring payments
- International payments
- API: REST, documentation: excellent
PayPal:
- PayPal and card payments
- Popular worldwide
- Simple implementation
- API: REST
Square:
- Payment processing
- Point of sale
- Good for US market
- API: REST
2. CRM and customer management
HubSpot:
- CRM, marketing automation
- Integrations with email, social media
- Free plan available
- API: REST, GraphQL
Salesforce:
- Enterprise CRM
- Advanced features
- High costs
- API: REST, SOAP
Pipedrive:
- Simple CRM for small businesses
- Focus on sales
- Reasonable prices
- API: REST
3. Email marketing
SendGrid:
- Transactional emails
- Marketing campaigns
- Good deliverability
- API: REST
Mailchimp:
- Email marketing
- Campaign automation
- Free plan available
- API: REST
Resend:
- Modern transactional emails
- Simple API
- Good prices
- API: REST
4. Analytics and tracking
Google Analytics:
- Traffic tracking
- Conversion tracking
- Free
- API: REST
Mixpanel:
- Event tracking
- User analytics
- Advanced features
- API: REST
Segment:
- Customer data platform
- Integrations with many tools
- Data centralization
- API: REST
5. Communication
Twilio:
- SMS, voice, video
- International
- Good API
- API: REST
SendGrid (SMS):
- SMS messaging
- Simple implementation
- Good prices
- API: REST
How to implement API integration?
1. API selection
- Check documentation – is it clear and complete
- Check limits – rate limits, costs
- Check support – is there community, support
- Check security – does it use HTTPS, OAuth
2. Authorization
- Get API key – register in the service
- Configure OAuth – if required
- Store securely – use environment variables (.env)
3. Implementation
- Use SDK – if available (easier)
- Or REST client – axios, fetch in JavaScript
- Handle errors – retry logic, error handling
- Test – use sandbox/test environment
4. Webhook
- Configure endpoint – URL that will receive webhook
- Verify signature – check if webhook is authentic
- Handle asynchronously – webhook can arrive anytime
- Log – log webhooks for debugging
Best practices
1. Security
- Use HTTPS – always encrypt communication
- Don't commit API keys – use .env, don't commit to Git
- Verify webhooks – check signature before processing
- Rate limiting – limit number of requests
2. Error handling
- Retry logic – retry request on error
- Timeout – set timeout for requests
- Error handling – handle all possible errors
- Logging – log errors for debugging
3. Performance
- Cache – cache responses when possible
- Batch requests – combine multiple requests into one
- Async processing – process webhooks asynchronously
- Monitoring – monitor API response time
Integration examples
Stripe – payments
// One-time payment
const payment = await stripe.paymentIntents.create({
amount: 2000, // $20.00
currency: 'usd',
payment_method: 'pm_card_visa',
});
// Subscription
const subscription = await stripe.subscriptions.create({
customer: 'cus_xxx',
items: [{ price: 'price_xxx' }],
});
SendGrid – email
// Transactional email
await sgMail.send({
to: 'user@example.com',
from: 'noreply@example.com',
subject: 'Welcome!',
html: '<h1>Welcome to our service!</h1>',
});
HubSpot – CRM
// Add contact to CRM
await hubspot.contacts.create({
email: 'user@example.com',
firstname: 'John',
lastname: 'Doe',
});
API integration costs
Free (with limits)
- Google Analytics
- Mailchimp (up to 500 contacts)
- HubSpot (free plan)
Paid
- Stripe: 2.9% + $0.30 per transaction
- SendGrid: from $15/month
- Twilio: from $0.0075/SMS
- Mixpanel: from $25/month
Summary
API integrations allow extending app functionality without building everything from scratch. Choose API with good documentation, secure authorization and appropriate limits. Remember about security, error handling and performance. Popular APIs are Stripe (payments), SendGrid (email), HubSpot (CRM) and Google Analytics (analytics).
Want to implement API integrations?
- Contact – tell us about your project
- See our implementations – examples of integrations
- Check our process – how we work