Frequently Asked Questions
Everything you need to know about OnChange. If your question is not answered here, reach out to us at contact@onchange.app.
What is OnChange?
OnChange is a website change detection and monitoring platform. It watches web pages and API endpoints on your behalf and alerts you the moment something changes. You can monitor entire pages, specific elements using CSS selectors, or API responses. Notifications are delivered via email, Slack, Discord, or custom webhooks.
How does OnChange detect changes?
OnChange periodically fetches your target URL over HTTP (the default for text and API monitors), captures the content, and compares it against the previous snapshot. Monitors can optionally render the page in a real headless browser for JavaScript-heavy sites (available on Pro and up). When a difference is detected, it generates a diff showing exactly what changed and sends notifications through your configured channels.
What types of websites can I monitor?
OnChange can monitor any publicly accessible web page, server-rendered HTML pages, and REST API endpoints. Standard text monitors fetch the page over HTTP. For JavaScript-heavy single-page applications (React, Vue, Angular, etc.), you can enable headless browser rendering per monitor on the Pro plan and up.
How often can OnChange check for changes?
Check intervals depend on your plan. Free monitors every 30 minutes, Pro every minute, Business every 30 seconds, and Enterprise as often as every 10 seconds. You can also set any custom interval in seconds (minimum 10s on Enterprise, maximum 1 year). Most users find 5-15 minute intervals work well for routine monitoring; flash-sale and time-sensitive use cases are what the sub-minute tiers are for.
What notification channels are supported?
OnChange supports email, Slack (via incoming webhooks), Discord (via webhooks), and custom HTTP webhooks. You can configure multiple notification channels per monitor, and different monitors can use different channels. Webhook payloads include structured data that can be parsed by automation tools like Zapier or Make.
Can I monitor specific parts of a page?
Yes. CSS selector targeting lets you monitor a specific HTML element instead of the whole page. This is the recommended approach for most use cases because it eliminates noise from dynamic content like ads, timestamps, and personalized sections. You can use the visual element picker in the dashboard or manually enter CSS selectors.
Does OnChange support visual (screenshot) comparisons?
Yes, on the Pro plan and up. OnChange takes screenshots of monitored pages and provides visual diffs that highlight pixel-level differences. This is particularly useful for detecting layout changes, styling updates, image replacements, and other visual modifications that text-based monitoring might miss.
Can I take a screenshot of a page without setting up a monitor?
Yes. Our free screenshot tool at /tools/screenshot captures any public URL as a PNG in seconds - no sign up required. Pick a viewport (desktop, tablet, mobile), optionally target a specific element by CSS selector, and download the image. If you want to be notified when that page changes in the future, one click turns the URL into a live monitor.
Can I monitor API endpoints?
Yes. OnChange can monitor REST API endpoints and detect changes in JSON response payloads. You can configure custom headers, authentication tokens, HTTP methods, and request bodies. JSON diffs show exactly which fields changed, were added, or were removed. See our API monitoring use case for details.
Is there a free plan?
Yes. The Free plan includes 5 monitors with 30-minute check intervals, email / Slack / Discord / webhook alerts, CSS selector targeting, WCAG accessibility scans, and full REST API access. Paid plans unlock more monitors, faster check frequencies, and additional features: visual diffs, JavaScript rendering, and AI-powered change summaries start on Pro, and multi-region monitoring starts on Business.
How is pricing structured?
Every plan includes the full REST API, all alert channels, and team collaboration. Tiers differ in (1) how many monitors you can create, (2) how fast checks can run, and (3) feature depth: visual diffs, JavaScript rendering, and AI summaries start on Pro; multi-region monitoring starts on Business. Free is for evaluation, Pro for solo developers, Business for growing companies, and Enterprise for mission-critical workloads. There are no hidden fees for alerts, channels, or data storage.
What is semantic-only alert mode?
Semantic-only mode is a per-monitor setting (available on the Pro plan and up) where Claude judges whether the meaning of the page actually changed and only alerts you on meaningful changes. Reworded, reordered, or re-rendered content that says the same thing is still recorded in your history, but it stays silent so it does not fill your inbox with noise. It is designed for pages that churn cosmetically but rarely change substance.
Can I see exactly what changed on a page?
Yes, on every plan. Open any change and the comparator shows the old and new versions side by side with the changed text marked in place - added text and removed text are highlighted where they occur. For visual monitors you also get a before/after screenshot slider, plus a section-level redline so you can jump straight to the part of the page that moved.
Can OnChange trigger automations when a change is detected?
Yes, on the Business plan and up. When a change qualifies - by severity, category, or whether the meaning changed - OnChange POSTs a structured payload to a webhook or workflow. That works with Zapier, Make, n8n, or your own internal endpoints, so a detected change can open a ticket, post to a channel, or kick off any downstream job.
Does OnChange offer an RSS or JSON feed of changes?
Yes, on every plan. Every monitor exposes a public, tokened RSS 2.0 feed and a JSON feed of its changes, each entry carrying the AI summary, category, severity, and semantic verdict. You can subscribe in any RSS reader, a Slack RSS app, or Zapier to pull changes into wherever your team already works.
Is my data secure?
All data is transmitted over TLS (HTTPS), and sensitive fields such as monitor credentials and integration secrets are encrypted at the application layer before storage. Monitored page data is isolated per account and never shared or sold. We're GDPR-ready. Enterprise security reviews, DPAs, and custom data-residency requirements are handled on the Enterprise plan - contact contact@onchange.app.
How long is change history retained?
OnChange retains change history for 90 days on every plan today. Enterprise customers can request longer retention as part of their contract. All change records include timestamps, before/after snapshots, and the full diff data for the duration of the retention window.
Can I access OnChange via an API?
Yes. OnChange provides a full REST API that lets you create, update, delete, and query monitors programmatically. You can also retrieve change history, diff data, and account information via the API. This enables integration with CI/CD pipelines, custom dashboards, and automation workflows.
Can I monitor pages that require login?
For API endpoints, you can configure custom headers with authentication tokens (Bearer tokens, API keys, basic auth). For web pages behind login walls, support depends on the authentication method. Contact us at contact@onchange.app if you need to monitor authenticated web pages.
What happens if a monitored page goes down?
If OnChange cannot load a monitored page (due to a server error, timeout, or network issue), it records the failure and can optionally alert you about the outage. This effectively provides basic uptime monitoring alongside change detection. The monitor continues checking on schedule and resumes normal operation when the page becomes available again.
Can I export my monitoring data?
Yes. You can export change history and monitoring data via the REST API. This allows you to build custom reports, import data into spreadsheets or BI tools, or archive records for compliance purposes. API responses are in standard JSON format for easy integration.
Is there a free tool to check a website for changes?
Yes. The OnChange website change checker is a free, public tool with no signup required. Paste any public URL to capture a baseline, come back within 24 hours, and it re-fetches the page and shows exactly what was added or removed, marked in place before and after side by side. It is a manual, on-demand check; one click turns any check into a live monitor that watches the page for you and alerts you automatically. You can try it at /tools/change-checker.
Can I silence alerts overnight or during off-hours?
Yes, with quiet hours. Set a daily do-not-disturb window in your own timezone and OnChange holds email alerts during that window, then delivers them as a single catch-up digest when it ends, so you wake up to one summary instead of a flood of overnight emails. You can optionally let critical changes bypass quiet hours and alert you immediately. Quiet hours are available on all plans.
How do I get support?
For general questions, check this FAQ page and our how-to guides. For account-specific issues or feature requests, contact us at contact@onchange.app. We aim to respond to all support requests within one business day.
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