Related: How to Secure a Web Application
Webhooks and APIs both let software talk to other software. People often mix them up or ask which one to use. The short answer is that they are not rivals. An API is how you ask for data when you want it. A webhook is how a service tells you the moment something happens. This guide explains the difference in plain terms. It covers push versus pull, when each one fits, reliability and retries, and security like signatures, with real examples.
Key takeaways
- An API call is pull. Your app asks for data when it needs it.
- A webhook is push. The other service sends data to you when an event happens.
- Use an API for on demand reads, writes, and actions you control.
- Use a webhook for instant updates, so you do not poll over and over.
- Webhooks need retries, since the receiver can be down for a moment.
- Verify webhook signatures so you know the message is real and not faked.
The core difference
An API, in the common web sense, is an endpoint you call. Your app sends a request and gets a response back right away. You are in control of when it runs. You decide to fetch a customer, create an order, or update a record. Nothing happens until you ask.
A webhook flips this around. You give another service a URL that you own. When an event happens on their side, they send an HTTP request to your URL. You do not ask for it. You just receive it. A webhook is really just an API call, but the direction is reversed.
So the difference is direction and timing. With an API you reach out. With a webhook the data comes to you. Both use the same HTTP building blocks underneath.
Push versus pull
The clearest way to think about this is push versus pull.
| Aspect | API (pull) | Webhook (push) |
|---|---|---|
| Who starts | Your app starts the request | The other service starts the request |
| Timing | Whenever you choose | The moment an event happens |
| Freshness | Only as fresh as your last call | Near real time |
| Cost | Wasted calls if nothing changed | No call until there is news |
| Setup | Simple, just call the endpoint | You must host a public URL |
Polling is the pull pattern taken to an extreme. Polling means you call an API again and again to check for changes. Most of those calls return nothing new. That wastes resources. A webhook removes this waste. The service only contacts you when there is real news.
When each one fits
Pick the tool that matches the job. Often you use both in the same product.
An API is the better fit when:
- You need data right now, in response to a user action.
- You are reading or writing on your own schedule.
- You need an exact answer to a specific question, like one order by its id.
- You are doing a one time job, such as a report or a bulk import.
A webhook is the better fit when:
- You want to react the moment something changes on another service.
- You would otherwise poll an API over and over for updates.
- Events are the natural unit, like a payment, a new signup, or a shipped order.
- You want to avoid delay between an event and your response.
A simple rule helps. If you ask for it, use an API. If you want to be told about it, use a webhook. Many real systems combine the two. A webhook tells you an event happened, then you call the API to fetch the full details.
Reliability and retries
APIs and webhooks fail in different ways, so they need different care.
With an API call, your app is awake and waiting. If a call fails, you see the error and can try again. You control the retry.
With a webhook, the risk is on the receiving side. Your server might be down, slow, or restarting when the event fires. Good webhook senders handle this with these patterns:
- Retries. If your endpoint does not return a success, the sender tries again later.
- Back off. Each retry waits a bit longer than the last, to avoid hammering you.
- A success signal. You should return a 200 status fast to confirm you got it.
- Idempotency. Retries can deliver the same event twice, so you must handle duplicates safely.
Two practices make webhook receivers reliable. First, accept the event, store it, and return 200 quickly. Do the slow work afterward in a background job. Second, use an event id to skip events you have already processed, so a repeated delivery does not create a second order or a double charge.
Security and signatures
A webhook URL is public, so anyone could try to send fake events to it. You must prove that a message really came from the right sender. The common method is a signature.
Here is how signatures usually work. The sender and you share a secret key. When the sender posts an event, it signs the body with that secret, often using HMAC. It puts the result in a header. When you receive the event, you compute the same signature on the raw body using your copy of the secret. If your value matches the header, the event is genuine. If not, you reject it.
- Always use HTTPS so the data is encrypted in transit.
- Check a timestamp in the request to block replayed old events.
- Keep the secret out of your code, in a safe environment variable.
- Optionally limit which sender IP ranges you accept, if the provider lists them.
Real examples make this concrete. Stripe sends webhooks for payment events and signs them with a secret. GitHub sends webhooks when code is pushed and includes a signature header. Both expect you to verify the signature before you trust the data.
FAQ
Can a service offer both webhooks and an API?
Yes, and most good ones do. The API lets you pull data and take actions. The webhooks push you updates as events happen. A common flow is to receive a webhook, then call the API to load the full record before you act on it.
What happens if my webhook endpoint is down?
The sender usually retries for a while with longer gaps between tries. If your endpoint stays down too long, you can miss events. To recover, many providers offer an API to list recent events, so you can backfill what you missed once you are back up.
Are webhooks hard to test?
They are a little harder than APIs because the call comes to you. During development you can use a tunneling tool to expose your local server to the internet. Many providers also offer a dashboard to resend test events, which makes debugging much easier.
Working with Apex Logic
We design and build integrations that use APIs and webhooks together. We set up reliable receivers with retries, idempotency, and signature checks, so your data stays correct and secure. If you are connecting payments, automating workflows, or wiring up an AI chatbot, see our services or contact us.
References
Stripe documentation on webhooks, signature verification, and event retries.
GitHub documentation on webhook delivery and securing payloads.
MDN Web Docs on HTTP requests, status codes, and HTTPS.
Comments