Check Types

Pick the check type in the first step of the monitor editor. This page lists what each type tests, its settings (the Request step) and what it can assert (the Assertions step).

HTTP

Assertions: Status code, Response time (ms), Body (raw, JSONPath, XPath or JSON Schema), Header, Body hash (SHA256, SHA1, MD5), Body size (bytes), Certificate (expiry in days, issuer, subject, SAN, TLS version) and JavaScript.

Each request carries a W3C traceparent header, so a run links to its backend trace in KubeSense when the service is traced, and an X-Kubesense-Synthetics header with the monitor id, so you can recognise synthetic traffic in your logs.

TCP

Assertions: Connection (established, refused, timeout), Received data, Response time, Network hops, Certificate and JavaScript.

DNS

Assertions: Every record, At least one record, Answer count, Authenticated data (with DNSSEC), Response time and JavaScript.

SSL

Assertions: Certificate properties (expiry in days, issuer, subject, SAN, TLS version) and Response time.

When the certificate enters the warning or critical window, the monitor raises an SSL expiry alert and is listed in SSL expiring soon on the Overview; the check still passes. An expired or invalid certificate fails the check.

gRPC

Assertions: Health status, gRPC status, Response message, Metadata / trailer, Response time, Certificate and JavaScript.

ICMP

Assertions: Packet loss (%), Packets received, Latency (ms, average, min, max or jitter) and Network hops.

The agent needs the NET_RAW capability (see Locations & Agents).

WebSocket

Target is a ws:// or wss:// URL.

Assertions: Received message, Header, Response time, Certificate and JavaScript.

UDP

Assertions: Received message, Response time and JavaScript.

Multistep API

A chain of steps run in order, where later steps use values extracted from earlier ones — for example, log in, then call an API with the token.

• Add step adds a step of type HTTP, gRPC, SSL, DNS, TCP, UDP, WebSocket, ICMP, MCP, Wait or Subtest (play another multistep monitor, with overrides). Up to 10 steps by default.
• Each step has its own settings and Assertions, a Step timeout, Step retries, and execution options: Allow failure, Critical, Exit if succeeded and Always execute.
• Extract variables takes a value from a step's response (a header, the body with a regex, JSONPath or XPath, the status code, and so on) into a variable used by later steps as {{ NAME }}. Mark it Secure to mask it in results. Extract from script does the same with JavaScript.
• Share cookies between steps keeps one cookie jar for the whole run.
• The Run budget in the schedule step limits the whole test (up to 30 minutes).

Browser Test

A user journey in headless Chromium. It needs a browser agent in at least one of the monitor's locations (see Deployment and Locations & Agents).

Steps (up to 50):

• Elements are found by CSS selector, or XPath with the xpath= prefix, with up to 5 alternatives per step.
• Import from recorder loads steps recorded with the browser recorder extension.
• Test the journey → Run test runs the journey once while you build it.
• Each run records a screenshot per step, the console, network requests and Web Vitals. See Monitor Details & Runs.
• Plan about 1 vCPU and 1 GiB on the browser agent per test running at the same time.

MCP Server

Checks a Model Context Protocol server over Streamable HTTP.

Assertions: Follows the MCP specification, Server capabilities, Tool count, Longest tool name, MCP response, Response time and Certificate. Presets adds a common set in one click.

Network Path

Traces the route to a host, like traceroute, and measures end-to-end latency and loss.

Assertions: Latency, Packet loss, Jitter and Network hops. The run shows a hop table with each router's address, name, round-trip time and loss.

TCP paths run without extra privileges. UDP and ICMP paths, and router names, need networkPath.rawSocket=true on the agent.

Kubernetes

Checks the health of a resource in the cluster where the agent runs. It needs an agent installed with the synthetics-agent chart and k8sChecks=true; the in-cluster agents of the KubeSense chart do not run it.

Kubernetes checks have no separate assertions: the check itself passes or fails.

JavaScript Assertions

HTTP, TCP, DNS, gRPC, WebSocket and UDP monitors (and those multistep steps) accept a JavaScript assertion. It passes unless the script throws or returns false:

dd.expect(dd.response.statusCode).to.equal(200);
dd.expect(dd.response.bodyJSON.items.length).to.be.above(0);

dd.response holds the status code, headers, body and timings; dd.variables holds the monitor's variables (secure values masked). Scripts run in a sandbox without network access, with a short CPU limit.