Know when your page content changes
Vantaj checks the response body of your HTTP endpoints on every check cycle. If an expected keyword disappears — or an unexpected one appears — you're alerted immediately.
Response body assertions
Assert that a keyword or phrase is present in the response. Catch broken pages, missing content, and partial deploys that return 200 but serve the wrong thing.
Negative assertions
Alert when a keyword you never want to see — like "error", "maintenance", or a competitor's name — appears in a response.
Runs on every check
Keyword assertions run on the same schedule as your uptime checks — as fast as every 30 seconds. No separate polling layer.
Same alert pipeline
Keyword failures route through your existing alert policies: Slack, email, webhooks, and more — no extra setup.
Combine with status code checks
Use keyword assertions alongside HTTP status code checks. A page that returns 200 but shows an error message will still trigger an alert.
Logged with check history
Every check records the outcome of your keyword assertions. Review exactly when content changed and how long an issue persisted.
What you can assert
| Assertion type | Example use case |
|---|---|
Contains keyword | Ensure "Add to cart" is present — confirms the product page rendered correctly |
Does not contain keyword | Alert if "502 Bad Gateway" or "Under maintenance" appears in any response |
Response body substring | Check for API response fields like `"status":"ok"` or `"loggedIn":true` |
Page title or heading | Verify the correct page title is served — catches misconfigured redirects |
How it works
Open Advanced settings
When adding or editing an HTTP monitor, expand the Advanced settings section to find keyword assertion fields.
Type what you expect to see
Enter a word or phrase that must be present in the response body. Optionally add a "must not contain" assertion for error strings.
Checked on every probe cycle
On each check, Vantaj fetches the page, verifies the status code, and evaluates your keyword assertions. A mismatch opens an incident immediately.
Notification through your existing channels
Keyword failures trigger the same alert policies as downtime events. Your team is notified via Slack, email, or webhook within seconds.
Frequently asked questions
Is keyword monitoring included on all plans?
Can I assert on JSON API responses?
What happens if the keyword is in a comment or hidden element?
Can I use multiple keyword assertions on one monitor?
Ready to set up Keyword Monitoring?
Up and running in under a minute. Free for up to 20 monitors, no credit card required.
Start for free