APIs and webhooks: what they are and when to use each one

An API is an interface that lets one application request information or perform an action in another system.

For example, an application can use a payments platform’s API to:

• Check the status of a transaction
• Create a refund
• Retrieve customer information
• Review payment history

In this model, the application that needs the information starts the conversation. It must make a request to the API and wait for a response.

A simple way to think about it: an API is a service you go to when you need something. The other system does not reach out on its own — you are the one who asks.

A webhook is a mechanism that lets one application notify another when an event happens.

Instead of repeatedly checking whether something has changed, the system that produces the event sends a notification to a URL you configured in advance.

For example, a payments platform can send a webhook when:

• A payment is completed
• A transaction is declined
• A refund is created
• A subscription is canceled

When the application receives that notification, it can run one or more actions. Those actions may be automatic — updating an order, sending data to another system, or starting an internal process. They can also create manual work, such as alerting a team to review an operation.

The main advantage of a webhook is that it lets you react quickly without polling the API over and over.

The clearest difference between an API and a webhook is who starts the communication.

With an API, our application asks:

“Has anything new happened?”

With a webhook, the other system tells us:

“This event just happened.”

That does not mean one is always better than the other. The choice depends on what the product needs.

An API is especially useful when the application needs information at a specific moment. A webhook is more convenient when the system should react as soon as an event occurs.

Webhooks are especially useful in automations that need some immediacy.

Imagine an online store. When a customer completes a payment, the system may need to:

• Mark the order as paid
• Update inventory
• Notify logistics
• Send a confirmation to the customer
• Log the transaction in a finance tool

Polling the payments API every few seconds to see whether the transaction completed would be inefficient. In this case, a webhook lets the payments platform announce the event so the store can start the process right away.

Other common cases include creating a user, signing a document, updating a shipment, receiving a form submission, or changing a task’s status.

Webhooks also make it easier to connect applications. The same event can be stored, transformed, and sent to different systems, so each tool does not have to keep querying the original source.

Not every process needs to run the instant an event happens.

Some actions should follow a schedule, batch information together, or control how many requests hit an API. In those cases, scheduled calls can be a better fit.

For example, a company might receive customer-related notifications throughout the day but only send emails during business hours. It might also collect several events and process them every fifteen minutes to avoid exceeding an external API’s rate limits.

A scheduled call lets you control:

• When the process runs
• How many requests are made
• How many events are processed in each batch
• Which actions should wait until a specific time window

So the need for immediacy should not be judged in isolation. The team also has to weigh technical limits, business rules, and the impact of the automation.

In many cases, the best solution combines webhooks and APIs.

A webhook can receive the notification immediately and store it in a queue, gateway, or intermediate system. Later, another process can run the needed actions at the right time.

This approach separates two responsibilities:

• Receive and record the event so it is not lost
• Process it when the right conditions are in place

For example, a webhook can record that a customer requested documents at 10 p.m. The notification is saved immediately, but the email goes out the next morning.

You can also use the webhook as the initial signal and then call an API for fuller details. The webhook says something happened; the API provides the up-to-date data needed to process the event.

APIs are not inherently more secure than webhooks. Security depends on how each mechanism is implemented.

An API usually uses keys, tokens, or credentials to authenticate requests. With webhooks, the receiving application must verify that the notification really came from the expected system. That can be done with cryptographic signatures, shared secrets, or header validation.

It is also important to assume a delivery can fail. The receiving server might be temporarily down or return an error. For that reason, a reliable system should plan for retries.

Retries should back off gradually, leaving more time between attempts. The application must also be ready to receive the same event more than once. Processing a payment, email, or update twice can cause serious errors.

A good practice is to assign a unique identifier to each event and keep track of which ones have already been processed.

APIs and webhooks should not be treated as rival technologies.

APIs let you request information or run actions when an application needs them. Webhooks let you react when an event happens, without repeatedly querying another system.

For a product team, the question is not simply which technology is better, but which behavior the product needs.

When an automation needs a fast reaction, a webhook is often a strong choice. When the process must run on a schedule, respect usage limits, or batch several operations, scheduled API calls can give you more control.

In many integrations, the most solid approach is to receive the event through a webhook, store it safely, and process it later with an API. That combination offers speed, flexibility, and a stronger foundation for reliable automations.