---
title: "Detect content changes on a page by comparing it against a stored baseline (create_baseline, then compare), or create a hosted monitor that checks it on a schedule (monitor)"
method: POST
path: "/tools/track_changes"
tags: ["tools"]
---

# Detect content changes on a page by comparing it against a stored baseline (create_baseline, then compare), or create a hosted monitor that checks it on a schedule (monitor)

`POST /tools/track_changes`

## Request

- Base URL: `https://www.crawlforge.dev/api/v1`
- URL: `https://www.crawlforge.dev/api/v1/tools/track_changes`
- Auth: API key in header `X-API-Key`

## Request body

- TrackChangesRequest
  - `url` string, uri, required: URL of the webpage to track
  - `operation` 'create_baseline' | 'compare' | 'monitor': create_baseline captures and stores the current page text (kept 90 days). compare fetches the page again and diffs it against the stored baseline. monitor creates a hosted monitor that fetches and compares the page on a schedule; creating it costs nothing, and each scheduled check bills 3 credits per target that was fetched and compared. Manage monitors at /api/v1/monitors or in the dashboard.
  - `selector` string: CSS selector to scope tracking to part of the page (e.g. ".pricing-table"). Baselines are stored per (url, selector) pair; 422 if the selector matches nothing.
  - `update_baseline` boolean: compare only: overwrite the stored baseline with the freshly fetched content after diffing
  - `respect_robots` boolean: create_baseline and compare: fetch the origin's robots.txt and refuse the URL if it disallows CrawlForge. A missing or unreachable robots.txt is treated as no restrictions. Returns 403 ROBOTS_DISALLOWED, and no credits are charged. Hosted monitors always respect robots.txt; a disallowed target is reported as a page error.
  - `schedule` string: monitor only: five-field cron expression, evaluated in UTC, for how often the monitor checks the page (default "0 * * * *", hourly). Consecutive runs must be at least 5 minutes apart; 400 VALIDATION_ERROR otherwise.
  - `notify_emails` string[]: monitor only: up to 5 addresses that receive a summary email when a check finds new, changed, blocked or errored pages
  - `webhook_url` string, uri: monitor only: an https endpoint that receives a signed POST (monitor.page per changed page, then monitor.check.completed) after every check. The signing secret is returned once, as webhook_secret on the created monitor.

## Response `200`

The tool's result; 3 credits charged (see x-credits-note and x-extra for add-ons).

- ToolSuccess: The envelope every tool returns on success. Credits are deducted only after the tool succeeded, so credits_used is the price of this call and an error response never charges.
  - `success` true, required
  - `data` object, required: The tool's result. Its shape is tool-specific and documented on the tool's docs page (x-docs-url on the operation).
  - `credits_used` integer, required: Credits charged for this call: the operation's x-credits, plus any add-on x-credits-note or x-extra describes.
  - `credits_remaining` integer, required: The account's credit balance after this call.
  - `processing_time` integer, required: Server-side processing time in milliseconds.
  - `warnings` string[]: Non-fatal notes: a robots.txt override that was recorded, a format that could not be produced, a redaction that changed the payload.

## Other responses

- `400`: VALIDATION_ERROR: the body does not match the request schema.
- `401`: MISSING_API_KEY or INVALID_API_KEY.
- `402`: INSUFFICIENT_CREDITS: the balance does not cover the tool's base price. X-Auto-Recharge-Triggered says whether an automatic recharge was started; retry once it lands.
- `429`: RATE_LIMIT_EXCEEDED: your plan's rate limit. Retry-After: 60.
- `500`: TOOL_ERROR, INTERNAL_ERROR or CREDIT_DEDUCTION_FAILED.
- `default`: Any other error. Which of 403, 404, 413, 422, 501, 502, 503 and 504 a tool can return depends on what it does (fetching a page, calling the execution backend, reading stored results); the code vocabulary is listed on the ErrorResponse schema.

---

[API](https://skmtc.dev/crawlforge/apis/crawlforge-rest-api.md) · [All operations](https://skmtc.dev/crawlforge/apis/crawlforge-rest-api/llms.txt) · [OpenAPI document](https://skmtc.dev/crawlforge/apis/crawlforge-rest-api/revisions/a5532fa8d5d5?raw)