Real User Monitoring Metrics

This page lists all the metrics that are reported by DebugBear's Real User Monitoring (RUM) feature. Use the API ID to access these metrics via the DebugBear API.

DebugBear RUM metric UI

Available RUM metrics

DebugBear RUM currently supports 37 different metrics.

Time to First Byte

The Full Time to First Byte measures how quickly the server responds to the HTML document request. This includes time spent establishing a server connection or on redirects. More details.

API ID: ttfb

First Contentful Paint

First Contentful Paint measures how quickly content appears on the page after navigation. For example, text and images count as content. More details.

API ID: fcp

Largest Contentful Paint

Largest Contentful Paint measures how quickly the largest page element appears. This could be a hero image or a big heading. More details.

API ID: lcp

Cumulative Layout Shift

Cumulative Layout Shift measures how stable the page layout is. Layout instability is when content shifts around on the page after being rendered. More details.

API ID: cls

Interaction to Next Paint

Interaction to Next Paint measures how quickly the page updates after the user interacts with it. More details.

API ID: inp

DOMContentLoaded Event

The DOMContentLoaded event timing measures when the initial page HTML has been parsed. This milestone occurs before dependent resources like async scripts or images are loaded. More details.

API ID: dcl

Load Event

The load event marks the time when the page has loaded including any dependent resources like scripts and images. While the Load event has long been used as a page speed metric, it was not designed to be one. Where possible, prefer a paint timing metric like FCP or LCP. More details.

API ID: load

TTFB Redirect

Time spent on same-origin redirects, for example if example.com/a returns a 301 status code and redirects to example.com/b. More details.

API ID: ttfbRedirect

TTFB Other

Various wait times, for example service worker processing or cross-origin redirects.

Check the referrer and UTM campaign breakdown to see if a cross-domain redirect is likely to delay TTFB. More details.

API ID: ttfbWait

TTFB DNS

Time spent looking up the IP address for the domain name. More details.

API ID: ttfbDns

TTFB TCP

Time spent establishing a reliable connection. More details.

API ID: ttfbTcp

TTFB SSL

Time spent establishing a secure connection. More details.

API ID: ttfbSsl

TTFB Response

Time spent waiting for the server to respond with the HTML document content. More details.

API ID: ttfbResponse

TTFB Download

Time spent downloading the HTML document. More details.

API ID: ttfbDownload

LCP Render Delay

Render delay measures how long it takes for the LCP element to become visible. More details.

API ID: lcpRenderDelay

LCP Load Duration

If the LCP element is an image the resource load time measures how long it takes to request and download the image. More details.

API ID: lcpLoadTime

LCP Load Delay

If the LCP element is an image the load delay measures how long after the document TTFB the image resource is discovered by the browser. More details.

API ID: lcpLoadDelay

LCP Processing Time

Duration of CPU tasks prior to the LCP milestone.

Not all main thread tasks are reported by the browser, so this metric represents a lower bound.

API ID: lcpCpuTime

Input Delay

The Input Delay component of the Interaction to Next Paint metric measures how much time elapses between the interaction and when the browser starts processing the event.

A high input delay suggests that background tasks may delay interaction processing. More details.

API ID: inputDelay

Processing Time

The Processing Time component of the Interaction to Next Paint metric measures how long it takes to run the JavaScript event handlers that handle the event. More details.

API ID: processingTime

Presentation Delay

The Presentation Delay component of the Interaction to Next Paint metric measures how soon after an interaction the main thread becomes idle and the browser can display the next rendering frame.

A high presentation delay can suggest complex rendering logic or a series of queued-up user interactions. More details.

API ID: presentationDelay

INP Primary Script Duration

Duration of script with the greatest contribution to the Interaction to Next Paint score.

API ID: inpPrimaryScriptDuration

LCP Script Duration

Duration of the longest single script that runs before the Largest Contentful Paint.

API ID: lcpScriptDuration

CLS Scroll Top

The visitor's scroll position on the page when the largest layout shift occurred.

Layout shifts often happen when the user scrolls down the page and new lazy-loaded content is added.

API ID: clsScrollTop

First-Party Page Weight

Download size for first-party requests on the page.

Browsers can't consistently report third-party resource sizes.

If resources are served from the browser cache this will result in a smaller page weight. More details.

API ID: fppwTotal

Browser Uncached Ratio

Percentage of requests that were served from a server rather than the browser cache. More details.

API ID: uncachedRatio

Error Count

The number of unhandled errors and promise rejections that were recorded.

API ID: errorCount

Network RTT

Rough round trip time (RTT) estimate that the browser provides through the Network Information API. More details.

API ID: networkRtt

Network Bandwidth

Rough bandwidth estimate that the browser provides through the Network Information API. More details.

API ID: networkBandwidth

Window Width

Outer width of the visitor's browser window.

API ID: windowWidth

Window Height

Outer height of the visitor's browser window.

API ID: windowHeight