Website Change Monitor – Text Diff Alerts

sfoln/website-change-monitor · Developer tools, Automation, SEO tools On request

Monitor web pages for changes: each run compares a page's text (or a CSS-selected part) with the last check and returns first seen, unchanged or changed with a line diff, similarity and added/removed lines. Ignore noisy text, add AI change summaries. $1 per 1,000 checks.

Request access Run it$1 / 1,000 page check, more below

About

What it does

Monitor web pages for changes and get a clear answer per URL on every run: first_seen, unchanged or changed — with a unified text diff, a similarity score, added and removed lines, and optionally an AI summary of what changed. Watch a whole page's main text or just the part you care about with a CSS selector (prices, job lists, terms, release notes), and ignore noise such as timestamps and counters. Built for competitor and pricing intelligence, compliance and policy tracking, procurement and job-board watching, SEO, and AI agents that need to know "has this page changed since yesterday?".

Price

Price per delivered record

Event	Price	Per 1,000	Charged for
Page check `page-check`	$0.001	$1 / 1,000	Charged once per URL checked: fetched, compared with its last snapshot and reported as first seen, unchanged or changed with a diff.
AI change summary `change-summary` paid plans only	$0.003	$3 / 1,000	Charged once per changed page for which the AI summary of the change (summary and significance) was generated. Paid plans only.

Apify free plan: up to 10 items per run. Paid plans have no per-run cap; set maxTotalChargeUsd to cap spend.

Run

Call it from code, an agent or the Console

This API is private on Apify for now. Email us and we will publish it for you, usually within two working days. The calls below work once it is public. contact@sfoln.com

curl · synchronous run, rows in the response

curl -X POST "https://api.apify.com/v2/actors/sfoln~website-change-monitor/run-sync-get-dataset-items" \
  -H "Authorization: Bearer $APIFY_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"urls":["https://example.com/"]}'

mcp.json · hosted Apify MCP server

{
  "mcpServers": {
    "apify": {
      "type": "http",
      "url": "https://mcp.apify.com?tools=sfoln/website-change-monitor"
    }
  }
}

asynchronous run · for large batches

POST https://api.apify.com/v2/actors/sfoln~website-change-monitor/runs?maxTotalChargeUsd=1
GET  https://api.apify.com/v2/actor-runs/{runId}            # until status is SUCCEEDED
GET  https://api.apify.com/v2/datasets/{defaultDatasetId}/items?format=json

Authenticate with an Apify API token. MCP clients can instead sign in with OAuth when prompted. Example prompt for an agent: Use website-change-monitor to check https://example.com/ for changes since the last check and tell me what changed.

Input

Input fields

Pages to check. Each run compares every page with its snapshot from the previous run (kept in a named key-value store in your account) and returns one record per URL. Schedule the Actor to get change alerts.

Field	Type	Default	Meaning
`urls` *	`array`	required	URLs Pages to monitor, one per line (public http(s) URLs). The first check of a URL saves its baseline. Accounts on the Apify free plan can process up to 10 URLs per run.
`selector`	`string`	—	CSS selector Watch only the elements matching this CSS selector (e.g. #pricing, .job-list li, table.prices tr). Empty: the page's main text (navigation, footer and scripts left out). Each selector keeps its own snapshot of a page.
`ignorePatterns`	`array`	—	Ignore patterns Regular expressions (case-insensitive), one per line: matching text is removed from each line before comparing, e.g. Last updated: .* or \d+ views. Changing them later applies to the stored snapshot too. Patterns that backtrack catastrophically, such as (a+)+ or (\w\|\d)+, are refused.
`ignoreNumbers`	`boolean`	`false`	Ignore numbers Treat all numbers as equal (counters, timestamps, prices), so only changes in wording count.
`summarizeChanges`	`boolean`	`false`	AI change summary (paid add-on) For changed pages, add a one-paragraph AI summary of what changed and its significance (minor, moderate, major). Charged per summary (change-summary); paid Apify plans only.
`diffContextLines`	`integer`	`2`	Diff context lines Unchanged lines shown around each change in the unified diff. Range 0–10.
`maxDiffChars`	`integer`	`5000`	Max diff length Characters of unified diff per page; a longer diff is cut (diffTruncated: true). Range 500–100000.
`excerptChars`	`integer`	`1000`	Text excerpt length Characters of the page's current text in textExcerpt (0 = none). Range 0–20000.
`includeText`	`boolean`	`false`	Include full text Add the full normalized page text (up to 200,000 characters) to each record.
`storeName`	`string`	—	Snapshot store name Named key-value store for the snapshots (letters, digits, hyphens). Default: website-change-monitor-memory. Use different names to keep separate monitors of the same pages apart; delete a record (or the store) to reset a baseline.
`maxUrls`	`integer`	`500`	Max URLs Safety cap on URLs in this run; the rest are ignored and counted as inputItemsDropped in the OUTPUT record. Range 1–5000.
`concurrency`	`integer`	`4`	Concurrency Pages checked in parallel. Range 1–10.

Example input

{
  "urls": [
    "https://example.com/"
  ]
}

Output

One record per input item

Records land in the run's dataset; a synchronous call returns them directly. Each has a status (ok is charged; everything else is free) and a charged flag. The run's OUTPUT record totals items and charges.

Field	Type	Meaning
`input`	`string \| object`	Input The URL this record corresponds to.
`status`	`string`	Status ok \| not_found \| error \| skipped_invalid \| skipped_budget \| skipped_free_plan \| skipped_unmetered e.g. `"ok"`
`charged`	`boolean`	Charged Whether this record incurred a pay-per-event charge.
`chargedEvent`	`string`	Charged event Pay-per-event event charged for this record (present only when charged).
`chargedCount`	`integer`	Events charged Events actually charged when the charge came back short of the requested count (present only then; a warning explains it).
`source`	`string`	Source Upstream data source.
`fetchedAt`	`string`	Fetched at ISO timestamp.
`error`	`object`	Error { code, message, provider?, status? } when status is not ok. Codes set by the runtime: budget_exhausted, free_plan_limit, unmetered, aborted, charge_failed, record_too_large, invalid_record, dataset_push_failed, memory_unavailable; fetch codes: http_<status>, invalid_url, blocked_url, dns_not_found, network, tls_error, timeout, too_many_redirects, unexpected_type, too_large; this Actor: selector_not_found, no_text, pattern_too_slow.
`warnings`	`array`	Warnings Notes, e.g. a page cut at 5 MB or a skipped AI summary.
`url`	`string`	URL The monitored URL.
`finalUrl`	`string`	Final URL The URL that answered, after redirects.
`httpStatus`	`integer`	HTTP status Status of the final response.
`title`	`string \| null`	Page title The page's <title>.
`contentType`	`string \| null`	Content type Declared media type.
`selector`	`string \| null`	Selector The CSS selector watched (null: the page's main text).
`selectorMatches`	`integer \| null`	Selector matches Elements the selector matched.
`changeStatus`	`string`	Change status first_seen (baseline saved) \| unchanged \| changed \| error (the page could not be checked; not charged).
`changed`	`boolean`	Changed True when the page changed since the previous check.
`similarity`	`number \| null`	Similarity 0–1 share of unchanged lines (1 = identical); null on the first check.
`addedLines`	`integer`	Added lines Lines added since the previous check.
`removedLines`	`integer`	Removed lines Lines removed since the previous check.
`diff`	`string \| null`	Diff Unified diff of the page text (- removed, + added), at most maxDiffChars.
`diffTruncated`	`boolean`	Diff truncated The diff was cut at maxDiffChars.
`addedSample`	`array`	Added lines (sample) Up to 10 added lines.
`removedSample`	`array`	Removed lines (sample) Up to 10 removed lines.
`textExcerpt`	`string \| null`	Text excerpt The start of the page's current text (excerptChars).
`textLength`	`integer`	Text length Characters of normalized text compared.
`lineCount`	`integer`	Lines Lines of normalized text.
`textTruncated`	`boolean`	Text truncated The page or its text was cut (5 MB / 200,000 characters).
`contentHash`	`string`	Content hash SHA-256 of the compared text (after ignore patterns).
`previousHash`	`string \| null`	Previous hash SHA-256 of the previous text, compared the same way.
`previousCheckedAt`	`string \| null`	Previous check When the snapshot compared with was taken.
`firstSeenAt`	`string`	First seen When the page was first checked.
`lastChangedAt`	`string \| null`	Last changed The last check that found a change.
`checkedAt`	`string`	Checked at This check.
`summary`	`string \| null`	AI summary What changed, in a few sentences (summarizeChanges, paid add-on).
`significance`	`string \| null`	Significance minor \| moderate \| major (AI summary).
`summaryCharged`	`boolean`	Summary charged The change-summary add-on was charged for this page.
`text`	`string`	Text The full normalized text (includeText).

Example record

{
  "input": "https://shop.example.com/pricing",
  "url": "https://shop.example.com/pricing",
  "finalUrl": "https://shop.example.com/pricing",
  "httpStatus": 200,
  "title": "Pricing",
  "contentType": "text/html",
  "selector": null,
  "selectorMatches": null,
  "changeStatus": "changed",
  "changed": true,
  "similarity": 0.75,
  "addedLines": 1,
  "removedLines": 1,
  "diff": "--- previous\t2026-10-13T12:00:00.000Z\n+++ current\t2026-10-14T12:00:00.000Z\n@@ -1,4 +1,4 @@\n Pricing\n Simple plans for every team, billed monthly or yearly.\n-Starter | $10\n+Starter | $12\n Pro | $49",
  "diffTruncated": false,
  "addedSample": [
    "Starter | $12"
  ],
  "removedSample": [
    "Starter | $10"
  ],
  "textExcerpt": "Pricing\nSimple plans for every team, billed monthly or yearly.\nStarter | $12\nPro | $49",
  "textLength": 86,
  "lineCount": 4,
  "textTruncated": false,
  "contentHash": "4f1c…",
  "previousHash": "9a0b…",
  "previousCheckedAt": "2026-10-13T12:00:00.000Z",
  "firstSeenAt": "2026-10-01T12:00:00.000Z",
  "lastChangedAt": "2026-10-14T12:00:00.000Z",
  "checkedAt": "2026-10-14T12:00:00.000Z",
  "summary": "The Starter plan price rose from $10 to $12 per month; the Pro plan is unchanged.",
  "significance": "moderate",
  "summaryCharged": true,
  "status": "ok",
  "charged": true,
  "chargedEvent": "page-check",
  "source": "website",
  "fetchedAt": "2026-10-14T12:00:00.000Z"
}

FAQ

Questions

Where are the snapshots stored?: In a named key-value store in your own Apify account (website-change-monitor-memory unless you set storeName), one record per URL and selector. Named stores are kept between runs; delete a record or the whole store to reset the baselines.
How do I get alerts?: Schedule the Actor (hourly, daily…) and add a webhook or a Make/Zapier/n8n integration that filters the dataset on changed = true.
Does it render JavaScript?: No. It compares the HTML the server sends. Pages that build their content in the browser return no text (status error, not charged); point the Actor at the page's JSON API or a server-rendered URL instead.
How do I stop false alarms from timestamps and counters?: Add ignorePatterns such as Last updated: .* or \d+ views, or turn on ignoreNumbers. Patterns are applied to both the stored snapshot and the new text, so you can tune them at any time.

Machine-readable

This page for agents

/actors/website-change-monitor.json — this API as JSON
/actors/website-change-monitor.md — this API as Markdown
/catalog.json — the whole catalogue