Frontend monitoring measures the experience your users actually get, in their browser, on their device, not just what your servers return.
Frontend monitoring is the practice of measuring the performance, availability and errors of the client side of an application, the web page or mobile app running in the user's browser or device, so you can see the experience real users actually get rather than only what the server returns.
Server-side metrics can look perfect while users are having a bad time. Once a response leaves your servers, a lot still happens: the browser downloads assets, parses and executes JavaScript, renders the page, and runs on whatever device and network the user has. A page can be served in milliseconds and still take seconds to become usable because of a heavy script, a large image, a slow third-party tag or a poor connection. Only the client can see that last mile, which is exactly the part that determines whether the experience felt fast. Frontend monitoring exists to close that gap between what the server did and what the user felt.
A frontend monitoring setup captures several things: page and resource load timing, the Core Web Vitals (loading, interactivity and visual stability), JavaScript errors and unhandled exceptions, the latency of API calls made from the browser, and user interactions and route changes. It comes in two complementary flavours. Real User Monitoring (RUM) captures this from actual user sessions, so it reflects the true diversity of devices, browsers and networks. Synthetic monitoring runs scripted checks on a schedule, giving consistent, proactive coverage even when no real user is active. Most mature teams use both.
The rise of single-page applications and heavy client-side rendering has pushed more and more work into the browser, which makes frontend monitoring more important, not less. In an SPA, a route change is not a fresh page load, so naive timing misses it; third-party scripts and CDNs introduce failure modes outside your own code; and errors that only occur on certain browsers or devices are invisible server-side. OpenTelemetry now has browser instrumentation and emerging conventions for this, so front-end telemetry can flow into the same pipeline as your backend traces, connecting a slow interaction to the server work behind it.
Ops Singularity ingests frontend telemetry over OpenTelemetry through its TelemetryOps pillar, correlated with the backend traces behind each interaction, and Sentinel AI acts on the incidents it reveals, a bad deploy spiking JavaScript errors, an API slow only from the browser, through governed Action Tickets, so front-end problems lead to resolution, not just a dashboard.
Backend monitoring measures your servers and services; frontend monitoring measures the client side, the browser or app, capturing rendering, JavaScript errors and the real user experience the server cannot see.
RUM (Real User Monitoring) is one form of frontend monitoring that captures data from real user sessions. Frontend monitoring also includes synthetic checks and error tracking.
Yes. OpenTelemetry has browser instrumentation for the JavaScript SDK, so page loads, interactions, errors and Core Web Vitals can be collected over OTLP alongside backend telemetry.
Ops Singularity turns open telemetry into autonomous, governed resolution. See it on your own stack.