Monitor websites, APIs, and web pages around the clock. The moment something shifts - you're the first to know.
Every check is plotted, so a spike in change activity surfaces the moment it happens.
Check any page for changes, no signup.
Hold alerts overnight; catch-up digest after.
Pro+: alert only when the meaning changes.
Old vs new side by side, changes marked in place.
Pro+: ask Claude about any before/after.
Try it
Change a price, reword a line, add a clause. OnChange marks exactly what moved, added in green and removed in red, the same way it watches your real pages. No signup.
Acme Cloud
This page is editable. Click a sentence and change it, or use a preset.
Features
Everything you need to stay ahead of changes - designed for developers and teams.
A keyboard-first changes inbox. Unreviewed / Useful / Noise / Archived columns with j/k navigation, u/n verdicts, e to archive. Noise verdicts mine repeated patterns and propose mask regexes.
Field-level JSON-Patch for API responses, section-anchored diffs for long HTML, SEO drift for head tags. The line diff is still there; the structured artefacts are what the UI and alert rules reason over.
Screenshot-based comparison detects pixel-level changes across your monitored pages.
Track JSON and REST endpoints with custom headers, authentication, and request bodies.
Route notifications to Slack, Discord, email, or webhooks - per monitor, your rules.
A per-monitor mode where Claude judges whether the meaning changed and only alerts on meaningful edits - reworded, reordered, or re-rendered content is still recorded but stays quiet. Available on Pro and up.
Open any change and read old vs new side by side with added and removed text marked in place, a before/after screenshot slider, and a section-level redline. On every plan.
Use cases
Pick the persona closest to your job and see the features that solve it.
Sitemap drift, robots.txt, and meta-tag diffs - caught before rankings move.
WCAG regressions tracked against an attested baseline, with client-ready VPAT evidence.
Prices and stock as time-series, with alerts that fire on threshold crossings.
API contract diffs with field-level JSON-Patch and GitHub commit attribution.
How it works
Paste any website, API endpoint, or page URL. Use CSS selectors to target specific elements.
Our infrastructure checks your URLs on schedule - text diffs, visual screenshots, or API tracking.
The moment a change is detected, you receive an alert with a detailed diff.
Pricing
Start free and scale with your needs.
Visual diffs, JavaScript rendering, and AI change summaries start on Pro. Multi-region monitoring starts on Business.
Monitoring playbooks
OnChange combines website change detection, visual diff monitoring, SEO monitoring, API tracking, and accessibility scans in one workflow. Use it to protect the pages and endpoints that customers, search engines, and internal teams rely on.
FAQ
Quick answers for teams comparing OnChange with uptime tools, visual diff tools, and manual QA checks.