This topic describes metrics that LaunchDarkly autogenerates from observability session replay events.
The LaunchDarkly observability session replay SDK plugins provide error monitoring and metric collection for errors, web vitals, and document loading in your browser application. The functionality is in separate plugins, which you enable in the initialization options for the LaunchDarkly SDK. The session replay plugins automatically collect and send data to LaunchDarkly, where you can review metrics, events, and errors from your application.
The observability events are prefixed with $ld:telemetry and LaunchDarkly automatically generates metrics from these events.
These expandable sections explain the metrics that LaunchDarkly autogenerates from events recorded by the observability plugins for LaunchDarkly browser SDKs:
Average Cumulative Layout Shift (CLS) per context (LaunchDarkly) $ld:telemetry:metric:cls
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average largest burst per context of layout shift scores for every unexpected layout shift that occurs during the entire lifecycle of a page.
Example usage: Observing the latency of interactions an end user makes with your application
P95 Cumulative Layout Shift (CLS) per context (LaunchDarkly) $ld:telemetry:metric:cls
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile largest burst per context of layout shift scores for every unexpected layout shift that occurs during the entire lifecycle of a page.
Example usage: Observing the latency of interactions an end user makes with your application
P99 Cumulative Layout Shift (CLS) per context (LaunchDarkly) $ld:telemetry:metric:cls
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile largest burst per context of layout shift scores for every unexpected layout shift that occurs during the entire lifecycle of a page.
Example usage: Observing the latency of interactions an end user makes with your application
Average Document Load Latency per context (LaunchDarkly) $ld:telemetry:metric:document_load
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average DOM load duration in milliseconds per context
Example usage: Observing the latency of interactions an end user makes with your application
P95 Document Load Latency per context (LaunchDarkly) $ld:telemetry:metric:document_load
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile DOM load duration in milliseconds per context
Example usage: Observing the latency of interactions an end user makes with your application
P99 Document Load Latency per context (LaunchDarkly) $ld:telemetry:metric:document_load
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile DOM load duration in milliseconds per context
Example usage: Observing the latency of interactions an end user makes with your application
User error rate (LaunchDarkly) $ld:telemetry:error
Metric kind: Custom conversion binary
Suggested analysis unit: User
Definition:
0Description:
Measures the percentage of contexts that encountered an error at least once. This metric is autogenerated by an initial $ld:telemetry:session:init event and populated by subsequent $ld:telemetry:error events. This means you can use the metric even if your app has not yet generated any errors.
Example usage: Running a guarded rollout to make sure the error change doesn’t result in a higher error rate
Average First Contentful Paint (FCP) per context (LaunchDarkly) $ld:telemetry:metric:fcp
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average time in milliseconds per context between first navigation to a page and when any part of the page’s content is rendered.
Example usage: Observing the latency of interactions an end user makes with your application
P95 First Contentful Paint (FCP) per context (LaunchDarkly) $ld:telemetry:metric:fcp
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile time in milliseconds per context between first navigation to a page and when any part of the page’s content is rendered.
Example usage: Observing the latency of interactions an end user makes with your application
P99 First Contentful Paint (FCP) per context (LaunchDarkly) $ld:telemetry:metric:fcp
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile time in milliseconds per context between first navigation to a page and when any part of the page’s content is rendered.
Example usage: Observing the latency of interactions an end user makes with your application
Average First Input Delay (FID) per context (LaunchDarkly) $ld:telemetry:metric:fid
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average time in milliseconds per context between a user’s first interaction (click, tap, or key press) and the time when the browser starts processing event handlers in response to that interaction.
Example usage: Observing the latency of interactions an end user makes with your application
P95 First Input Delay (FID) per context (LaunchDarkly) $ld:telemetry:metric:fid
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile time, in milliseconds per context, between a user’s first interaction (click, tap, or key press) and the time when the browser starts processing event handlers in response to that interaction.
Example usage: Observing the latency of interactions an end user makes with your application
P99 First Input Delay (FID) per context (LaunchDarkly) $ld:telemetry:metric:fid
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile time, in milliseconds per context, between a user’s first interaction (click, tap, or key press) and the time when the browser starts processing event handlers in response to that interaction.
Example usage: Observing the latency of interactions an end user makes with your application
Average Interaction to Next Paint (INP) per context (LaunchDarkly) $ld:telemetry:metric:inp
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average response time in milliseconds per context of all click, tap, and keyboard interactions during the lifespan of a visit to a page.
Example usage: Observing the latency of interactions an end user makes with your application
P95 Interaction to Next Paint (INP) per context (LaunchDarkly) $ld:telemetry:metric:inp
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile response time in milliseconds per context of all click, tap, and keyboard interactions during the lifespan of a visit to a page.
Example usage: Observing the latency of interactions an end user makes with your application
P99 Interaction to Next Paint (INP) per context (LaunchDarkly) $ld:telemetry:metric:inp
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile response time in milliseconds per context of all click, tap, and keyboard interactions during the lifespan of a visit to a page.
Example usage: Observing the latency of interactions an end user makes with your application
Average Largest Contentful Paint (LCP) per context (LaunchDarkly) $ld:telemetry:metric:lcp
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average time in milliseconds per context to render the largest image, text block, or video visible when first navigating to a page
Example usage: Observing the latency of interactions an end user makes with your application
P95 Largest Contentful Paint (LCP) per context (LaunchDarkly) $ld:telemetry:metric:lcp
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile time in milliseconds per context to render the largest image, text block, or video visible when first navigating to a page
Example usage: Observing the latency of interactions an end user makes with your application
P99 Largest Contentful Paint (LCP) per context (LaunchDarkly) $ld:telemetry:metric:lcp
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile time in milliseconds per context to render the largest image, text block, or video visible when first navigating to a page
Example usage: Observing the latency of interactions an end user makes with your application
Average Time to First Byte (TTFB) per context (LaunchDarkly) $ld:telemetry:metric:ttfb
Metric kind: Custom numeric
Suggested analysis unit: User
Definition:
Description: Measures the average time in milliseconds per context between the request for a resource and when the first byte of a response begins to arrive.
Example usage: Observing the latency of interactions an end user makes with your application
P95 Time to First Byte (TTFB) per context (LaunchDarkly) $ld:telemetry:metric:ttfb
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 95th percentile time in milliseconds per context between the request for a resource and when the first byte of a response begins to arrive.
Example usage: Observing the latency of interactions an end user makes with your application
P99 Time to First Byte (TTFB) per context (LaunchDarkly) $ld:telemetry:metric:ttfb
Metric kind: Custom numeric
Suggested analysis unit: Request
Definition:
Description: Measures the 99th percentile time in milliseconds per context between the request for a resource and when the first byte of a response begins to arrive.
Example usage: Observing the latency of interactions an end user makes with your application