# Changes and diffs

Every time Monitor re-checks a page, it compares what it found with that page’s previous check. When a watched attribute is different, Monitor records a change with the value before and after. This is how you find out that a title was rewritten, a canonical moved, or a page started redirecting, and exactly when it happened.

> **Before you start:** Monitor must be enabled for your workspace. It is set up by arrangement, so if you do not see the **Monitor** icon in the top bar, [contact us](/contact/).

## What is compared

Monitor watches these attributes on every page:

| Attribute | Severity recorded with the change |
| --- | --- |
| **HTTP status** | Critical |
| **Indexability** | Critical |
| **Canonical link** | Critical |
| **Robots directives** | Critical |
| **Redirect target** | Critical |
| **Page title** | Warning |
| **H1 heading** | Warning |
| **Meta description** | Warning |
| **Hreflang** | Warning |
| **Structured data** (the schema types on the page) | Info |
| **Open Graph title** | Info |
| **Open Graph image** | Info |
| Analytics tags | Warning |
| Custom elements you define | Recorded as changes |

To watch a value that is not on this list, such as a price or a published date, add a custom element under **Settings** > **Crawling & extraction**. See [Monitor site settings](/docs/monitor-settings/).

Body copy, images and scripts are not compared. A page that loses its content is caught by the **Empty page** check instead. Links are not compared either: broken internal links are reported by the **Links to a broken page** check. See [Issues and severity](/docs/issues-and-severity/).

The first check of a page is its baseline, so a newly added page has no changes until its second check.

## Which changes email you

A change to status, indexability, canonical, robots directives or redirect target is not emailed as a change. When it breaks something, the matching check opens instead, for example **Page not found** or **Not indexable**, so the same event is not reported twice.

A rewritten title, H1 or meta description, or a changed custom element, opens an Info incident: **Title changed**, **H1 changed**, **Meta description changed** or **Custom value changed**. These appear on the **Alerts** and **Changes** tabs but are not emailed by default, because most content edits are your team doing their job. To be emailed about them, raise the check’s severity under **Settings** > **Checks** to warning or critical. To hear about an edit on only a few pages, also add an alert rule for that check with a higher **Sensitivity**.

Analytics tracking disappearing from a page is the exception: **Analytics tracking removed** is a Warning, and every new site has an alert rule for it, so it can email you without any setup.

When the same change happens on many pages at once, for example a template change, Monitor bundles it into one incident rather than one per page. See [Alerts and incidents](/docs/alerts-and-incidents/).

## Find a change

The **Changes** tab lists recorded changes, most recent first. Narrow the list with:

- **Period**: **Last 24 hours**, **Last 7 days**, **Last 14 days**, **Last 30 days** or **Everything**.
- **Property**: **All properties**, or one watched attribute.

Each change shows the page and the **Before** and **After** values.

The site’s **Overview** also has a **Changes** chart of watched attributes that moved, per day, over the last 14 days. For one page’s changes, open the page and select **Tracked changes**.

## Reading a change

The time of a change tells you when Monitor first saw the new value, which is when it re-checked the page, not necessarily the moment the change went live. Important pages are re-checked as often as every 15 minutes, so their changes are timed closely; the least important pages may be up to 24 hours behind.

To trace a change to its cause, compare its time with your deploys, plugin updates and CMS edits around that time. A change that appears on many pages at the same moment usually has one cause, such as a theme, template or plugin update.

## Related

- [Alerts and incidents](/docs/alerts-and-incidents/)
- [Issues and severity](/docs/issues-and-severity/)
- [Pages and crawl activity](/docs/pages-and-crawl-activity/)
- [Monitor site settings](/docs/monitor-settings/)