Page monitors - Context.dev

A page target watches the visible text of one URL. Without instructions, detection is exact and any text difference is a change. With instructions, detection is semantic and a judge decides whether a difference matters.

Fields

Field	Default	Notes
`url`	Required	Public `http(s)` URL.
`include_selectors`	Main content	CSS selectors for the regions to watch, combined in document order. Omit it or send `[]` for automatic main-content extraction.
`exclude_selectors`	None	CSS selectors to remove before comparing. They win over `include_selectors`.
`instructions`	None	1–2,000 characters on what matters and what to ignore. Makes detection `semantic`.
`normalize_whitespace`	`true`	Ignore whitespace-only differences. Set `false` when spacing matters.
`actions`	None	Up to 5 browser actions run in order after load, before capture, on every run. Requires a paid plan and changes the run price. Changing actions starts a new baseline.

Each selector list takes up to 50 selectors of 1–2,048 characters.

How a run works

Every run fetches the page fresh and applies exclude_selectors, then include_selectors. If the filtered page has no usable text, the run fails with fetch_failed and the old baseline stays.

An exact monitor reports the first fetch that differs from the baseline.
A semantic monitor fetches the page again to confirm a difference before the judge sees it. The judge then applies confidence_threshold, described in Change detection.

Example

Watch only the incidents section of a status page and report new or resolved incidents.

{
  "name": "Status page incidents",
  "target": {
    "type": "page",
    "url": "https://status.example.com",
    "instructions": "Report new or resolved incidents. Ignore uptime percentages.",
    "include_selectors": ["#incidents"]
  },
  "change_detection": { "type": "semantic", "confidence_threshold": 0.8 }
}

Omit instructions and change_detection to get an exact monitor that reports any text change inside #incidents.

Targets: detection rules and how to update a target.
Runs and changes: what a page change contains.
Browser actions: the actions a page monitor can run before capture.