Feed Delta Monitor

Get only new and edited entries from RSS, Atom and JSON feeds across scheduled runs. Feed Delta keeps the history in your Apify account, so your workflow does not need its own deduplication database.

Pricing: $0.005 per successful feed check ($5 per 1,000 checks), with platform usage included. The Actor's pricing panel is authoritative.

What it does

• Reads public RSS 2.0, RSS 1.0/RDF, Atom and JSON Feed 1/1.1 documents.
• Identifies entries by ID/GUID, then URL, with a content fallback for unidentified entries.
• Detects new entries and revisions; unchanged entries stay out of changes.
• Preserves separate histories for each monitor and feed.
• Uses ETag and Last-Modified when the publisher supports them.
• Returns per-feed status, including a successful empty check when nothing changed.

Use it for release-note monitoring, research feeds, news pipelines and ingestion into downstream tools. It reads the supplied feed documents; it does not crawl linked articles or send messages.

Start a monitor

Create an Apify task with this input, then schedule the task. Keep the monitor ID stable.

{
  "feedUrls": ["https://www.jsonfeed.org/feed.json"],
  "monitorId": "release-monitor",
  "firstRun": "emit",
  "maxChangesPerFeed": 100
}

emit returns entries already present on the first run. Choose baseline to save them silently and return only subsequent additions or edits. A feed added to an existing monitor gets its own first-run baseline. A new monitor ID creates a separate history. Saved tasks may omit the monitor ID and use their task ID instead; direct/API runs must provide one.

Schedule runs at least five minutes apart and allow only one active run for a given monitor ID. Wait for a run to finish before retrying it. Use separate monitor IDs for independently scheduled consumers. Exact-once delivery and simultaneous runs against the same monitor are not supported.

Output and billing unit

Each successful feed check returns one dataset record with a changes array. Feed checks with zero changes, HTTP 304 checks and silent baseline creation are successful checks and are chargeable. HTTP/parsing failures are listed in the free OUTPUT summary and produce no paid dataset record. There is no separate per-article or run-start fee.

{
  "monitorId": "release-monitor",
  "feedUrl": "https://example.com/feed.json",
  "checkedAt": "2026-09-07T12:00:00.000Z",
  "status": "checked",
  "feedTitle": "Example releases",
  "format": "json-feed",
  "changeCount": 1,
  "remainingChanges": 0,
  "changes": [{
    "eventId": "deterministic-event-hash",
    "type": "new",
    "id": "release-1",
    "url": "https://example.com/releases/1",
    "title": "Example release",
    "contentText": "A new release is available.",
    "contentHtml": "",
    "summary": "",
    "publishedAt": null,
    "modifiedAt": null,
    "author": "",
    "tags": [],
    "identity": "entry-identity-hash",
    "identityBasis": "id",
    "revision": "content-revision-hash"
  }]
}

The example is synthetic. Actual hashes are 64 hexadecimal characters. To consume individual changes:

const changes = feedChecks.flatMap(check => check.changes);
// Keep eventId in your destination's unique-key field to reject replayed output.

Statuses are checked, not_modified, baseline_created and partial. remainingChanges reports entries held back by the output cap. On the next run, those entries can be returned if they remain in the publisher's feed. The free OUTPUT record contains feed errors, checked counts and any time/spending-limit stop. A run with some broken feeds can complete successfully; inspect its summary too.

At this price, 10 feeds checked daily for 30 days cost $1.50 in event fees; 10 feeds checked hourly cost $36. These are usage examples, not a revenue forecast. The minimum run budget is $0.005. Provide enough budget for every feed you want checked: a run stops once it cannot afford another check, so a permanently undersized budget can leave later feeds unchecked. Apify account plans and access to stored datasets after a run are governed by Apify's pricing.

Limits and delivery behavior

• Maximum 50 feeds per run; sequential requests, 15 seconds per request including redirects, 180-second processing budget checked between feeds. A current request may finish after that budget.
• Maximum 2 MB compressed and decompressed response, 2,000 entries per document and 8 MB normalized output. Maximum 1,000 emitted changes per feed per run; default 100.
• Public HTTP(S), standard ports, no URL credentials, no private-network destinations. No proxies, login, pagination, browser rendering or XML DTD/entity declarations.
• Full feed content is included when present. Treat feed text and HTML as untrusted input; sanitize it before display or execution in another system.
• History retains up to 20,000 identities per feed. Entries absent from the current document expire after 90 days; older identities can also be evicted at the cap. A changed monitor ID, deleted history, retention expiry or eviction can cause entries to be emitted again.
• If a publisher omits both an entry ID and URL, content is its identity. Editing that entry can appear as a new entry. Changes to fields outside the normalized output are not tracked. A feed that reuses one ID for conflicting entries is rejected.
• Feeds are snapshots. Items can disappear between checks; polling cannot recover entries that are no longer present. Absence is not reported as deletion.
• Delivery is at least once after interruptions: output becomes available before state advances. If a write, charge or checkpoint fails ambiguously, retrying can replay changes and incur another successful-check fee. eventId is stable across a replay of the same state transition. There is no cross-service atomic transaction.
• Persistent history is documented for repeated runs by the same Apify account. Accountless wallet/x402 persistence has not been verified and is not advertised.

Data and support

The Actor stores output in the caller's default dataset, the run summary in its default key-value store, and a named key-value store containing hashed identities, revision counters, timestamps, feed titles and HTTP validators. It does not send data to a separate developer server or analytics service. Apify manages platform storage; the developer's platform access is governed by Apify permissions. Delete the named store to reset a monitor. No authentication tokens belong in feed URLs.

Report reproducible problems through the Actor's Apify Issues tab. Include the run ID and a public example feed; never post private credentials.

Local development

Requires Node.js 22 or later.

npm ci --ignore-scripts
npm test
npm run demo

The demo fetches two public feeds twice and writes counts to docs/live-demo-results.json. It stores a local baseline under the ignored storage directory. It does not charge anyone or publish anything. npm start uses the Apify SDK; supply storage/key_value_stores/default/INPUT.json for local runs.

Deployment, pricing gates, maintenance and evidence requirements are recorded in docs/LAUNCH.md.