With Performance Monitoring, you can use attributes to segment performance data and focus
on your app's performance in different real-world scenarios.
After you click a trace name in the traces table (located at the bottom of
the
[*Performance* dashboard](https://console.firebase.google.com/project/_/performance)), you can drill down into
metrics of interest. Use the
**Filter** button
(top-left of the screen) to filter the data by attribute, for example:
.
## Default attributes
Performance Monitoring automatically collects a variety of default attributes depending
on the type of trace.
In addition to these default attributes, you can also
[create custom attributes](https://firebase.google.com/docs/perf-mon/attributes.md.txt#create-custom-attributes) on your
[custom code traces](https://firebase.google.com/docs/perf-mon/custom-code-traces.md.txt) to segment data by
categories specific to your app. For example, in a game, you can segment data by
game level.
### Default attributes for Apple and Android apps
All traces for Apple and Android apps collect the following attributes by default:
- App version
- Country
- OS level
- Device
- Radio
- Carrier
In addition, network request traces also collect the following attribute:
- MIME type
## Collecting user data
> [!IMPORTANT]
> **Collecting user data:** Performance Monitoring does not itself collect
> any personally identifiable information (PII), such as names, email
> addresses, or phone numbers. Developers can collect additional data using
> Performance Monitoring by creating custom attributes on custom code traces. Such data collected through
> Performance Monitoring should not contain information that personally identifies an
> individual to Google.
>
> Here's an example of a log message that *does not* contain
> personally identifiable information:
>
> ```java
> trace.putAttribute("experiment", "A");
> ```
>
> Here's an example that *does* contain personally
> identifiable information (***do not use*** this type of
> custom attribute in your app):
>
> ```java
> trace.putAttribute("email", user.getEmailAddress());
> ```
>
> Data that exposes any personally identifiable information is subject to
> deletion without notice.
## Create custom attributes
You can create custom attributes on any of your instrumented
[custom code traces](https://firebase.google.com/docs/perf-mon/custom-code-traces.md.txt).
Use the Performance Monitoring Trace API
([Swift](https://firebase.google.com/docs/reference/swift/firebaseperformance/api/reference/Classes/Trace.md.txt)
\|
[Obj-C](https://firebase.google.com/docs/reference/ios/firebaseperformance/api/reference/Classes/FIRTrace.md.txt))
to add custom attributes to custom code traces.
To use custom attributes, add code to your app that defines the attribute and
associates it with a specific custom code trace. You can set the custom
attribute anytime between when the trace starts and when the trace stops.
Note the following:
- Names for custom attributes must meet the following requirements:
- No leading or trailing whitespace, no leading underscore (`_`) character
- No spaces
- Max length is 32 characters
- Allowed characters for the name are `A-Z`, `a-z`, and `_`.
- Each custom code trace can record up to 5 custom attributes.
- Please ensure that custom attributes do not contain any information that
personally identifies an individual to Google.
Learn more about this guideline
> [!IMPORTANT]
> **Collecting user data:** Performance Monitoring does not itself collect
> any personally identifiable information (PII), such as names, email
> addresses, or phone numbers. Developers can collect additional data using
> Performance Monitoring by creating custom attributes on custom code traces. Such data collected through
> Performance Monitoring should not contain information that personally identifies an
> individual to Google.
>
> Here's an example of a log message that *does not* contain
> personally identifiable information:
>
> ```java
> trace.putAttribute("experiment", "A");
> ```
>
> Here's an example that *does* contain personally
> identifiable information (***do not use*** this type of
> custom attribute in your app):
>
> ```java
> trace.putAttribute("email", user.getEmailAddress());
> ```
>
> Data that exposes any personally identifiable information is subject to
> deletion without notice.
### Swift
**Note:** This Firebase product is not available on macOS, Mac Catalyst, watchOS targets.
```swift
let trace = Performance.startTrace(name: "CUSTOM_TRACE_NAME")
trace.setValue("A", forAttribute: "experiment")
// Update scenario.
trace.setValue("B", forAttribute: "experiment")
// Reading scenario.
let experimentValue:String? = trace.valueForAttribute("experiment")
// Delete scenario.
trace.removeAttribute("experiment")
// Read attributes.
let attributes:[String, String] = trace.attributes;
```
### Objective-C
**Note:** This Firebase product is not available on macOS, Mac Catalyst, watchOS targets.
```objective-c
FIRTrace *trace = [FIRPerformance startTraceWithName:@"CUSTOM_TRACE_NAME"];
[trace setValue:@"A" forAttribute:@"experiment"];
// Update scenario.
[trace setValue:@"B" forAttribute:@"experiment"];
// Reading scenario.
NSString *experimentValue = [trace valueForAttribute:@"experiment"];
// Delete scenario.
[trace removeAttribute:@"experiment"];
// Read attributes.
NSDictionary *attributes = [trace attributes];
```