---
title: "Tracing"
description: "Learn how to enable tracing in your app and get valuable performance insights about your application."
url: https://docs.sentry.io/platforms/apple/guides/ios/tracing/
---

# Set Up Tracing | Sentry for iOS

With [tracing](https://docs.sentry.io/product/insights/overview.md), Sentry tracks your software performance, measuring metrics like throughput and latency, and displaying the impact of errors across multiple systems. Sentry captures distributed traces consisting of transactions and spans, which measure individual services and individual operations within those services. Learn more about our model in [Distributed Tracing](https://docs.sentry.io/product/sentry-basics/tracing/distributed-tracing.md).

Automatic instrumentation for monitoring the performance of your application is currently in preview. You can also use custom instrumentation to capture transactions.

## [Configure](https://docs.sentry.io/platforms/apple/guides/ios/tracing.md#configure)

First, enable tracing and configure the sample rate for transactions. Set the sample rate for your transactions by either:

* Setting a uniform sample rate for all transactions using the `tracesSampleRate` option in your SDK config to a number between `0` and `1`. (For example, to send 20% of transactions, set `tracesSampleRate` to `0.2`.)
* Controlling the sample rate based on the transaction itself and the context in which it's captured, by providing a function to the `tracesSampler` config option.

The two options are meant to be mutually exclusive. If you set both, `tracesSampler` will take precedence.

```swift
import Sentry

SentrySDK.start { options in
    options.dsn = "___PUBLIC_DSN___"

+   // Example uniform sample rate: capture 100% of transactions
+   // In Production you will probably want a smaller number such as 0.5 for 50%
+   options.tracesSampleRate = 1.0

+   // OR if you prefer, determine traces sample rate based on the
+   // sampling context
+   options.tracesSampler = { context in
+       // Don't miss any transactions for VIP users
+       if context?["vip"] as? Bool == true {
+           return 1.0
+       } else {
+           return 0.25 // 25% for everything else
+       }
+   }
}
```

Learn more about tracing [options](https://docs.sentry.io/platforms/apple/guides/ios/configuration/options.md#tracing-options), how to use the [tracesSampler](https://docs.sentry.io/platforms/apple/guides/ios/configuration/sampling.md#setting-a-sampling-function) function, or how to [sample transactions](https://docs.sentry.io/platforms/apple/guides/ios/configuration/sampling.md#sampling-transaction-events).

## [Verify](https://docs.sentry.io/platforms/apple/guides/ios/tracing.md#verify)

Verify that tracing is working correctly by using our [automatic instrumentation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/instrumentation/automatic-instrumentation.md) or by starting and finishing a transaction using [custom instrumentation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/instrumentation/custom-instrumentation.md).

Test out tracing by starting and finishing a transaction, which you *must* do so transactions can be sent to Sentry. Learn how in our [Custom Instrumentation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/instrumentation/custom-instrumentation.md) content.

While you're testing, set `tracesSampleRate` to `1.0`, as that ensures that every transaction will be sent to Sentry. Once testing is complete, you may want to set a lower `tracesSampleRate` value, or switch to using `tracesSampler` to selectively sample and filter your transactions, based on contextual data.

## [Next Steps](https://docs.sentry.io/platforms/apple/guides/ios/tracing.md#next-steps)

* #### [Instrumentation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/instrumentation.md)

  Learn how to instrument tracing in your app.

* #### [Trace Propagation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/trace-propagation.md)

  Learn how to connect events across applications/services.

## Pages in this section

- [Instrumentation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/instrumentation.md)
- [Trace Propagation](https://docs.sentry.io/platforms/apple/guides/ios/tracing/trace-propagation.md)