Skip to content
/ Docs

Understanding Baselines

Every time you re-run a scan, Sitepager compares your site against a baseline. The baseline is your reference point, a capture of your site at a known-good state. Understanding how it works is key to getting the most out of every run.

How baselines are created

Section titled “How baselines are created”

Your first scan creates the baseline automatically. Sitepager captures every page on your site, visually and across all checks, and saves it as your starting baseline.

You do not need to create it manually. Run your first scan and it is set for you.

From that point on, every future run compares against it.

What a baseline contains

Section titled “What a baseline contains”

A baseline is tied to a specific scan. That scan has a URL, a device (desktop or mobile), and a region. The baseline captures:

  • A screenshot of every page discovered during the scan
  • The SEO state of every page (titles, descriptions, headings, alt text)
  • The link structure (internal and external)
  • The list of pages found

How comparisons work

Section titled “How comparisons work”

When you re-run a scan, Sitepager crawls your site again and compares the new results against the active baseline.

It matches pages by URL and checks for visual changes since the baseline. Pages that look different are flagged for review.

Some checks run independently of the baseline. Broken links, broken pages, and SEO gaps are flagged on every run whether or not they existed in the baseline. These are always surfaced because they are issues right now, regardless of what the baseline looked like.

Page changes are also compared against the baseline. If a page existed in the baseline but is missing now, it is flagged as removed. If a new page appears that was not in the baseline, it is flagged as added. This is how you catch pages that were accidentally deleted, or new pages that published without review.

The results page shows everything in one place:

  • Visual changes compared against the baseline
  • Pages added or removed since the baseline
  • Broken pages and links found on this run
  • SEO gaps found on this run

Review everything before you publish. Fix what needs fixing. Confirm what is intentional.

How baselines work

Section titled “How baselines work”

This diagram shows how Sitepager uses a baseline to compare changes across scans.

flowchart TD

A["1. Run your first scan to create the baseline"]
B["2. Run another scan to compare changes against the baseline"]
C["3. Run additional scans to continue comparing changes"]
D["4. Set a new baseline when you are happy with the current state of your site"]

A --> B
B --> C
C --> D
D -.->|future scans compare here| B

When to update your baseline

Section titled “When to update your baseline”

Update the baseline after you have reviewed your changes and published your update. This resets the reference point so the next run compares against the current version of your site.

To update it, open the results of a completed run and click Set as Baseline. A confirmation dialog will appear. Once confirmed, that run becomes the new active baseline for that scan.

The previous baseline is deactivated. It is not deleted, but it is no longer used for comparison.

Update after:

  • Publishing an update and confirming the changes are correct
  • A redesign, when you want future runs to compare against the new design

Do not update:

  • Before reviewing changes. If you update the baseline before reviewing, you lose your ability to compare what changed.
  • In the middle of an update cycle. Wait until you have reviewed, fixed any issues, and published.

One baseline per scan

Section titled “One baseline per scan”

Each scan has exactly one active baseline at a time. When you click Set as Baseline, the previous baseline is deactivated and the new one takes its place.

If you need to track different versions of your site independently, create separate scans.

Multiple scans, multiple baselines

Section titled “Multiple scans, multiple baselines”

Different scans have independent baselines. This is how you track different configurations of your site separately.

Common setups:

Desktop and mobile: create one scan for desktop and one for mobile. Each has its own baseline and run history. For example, a mobile scan for your main site and a desktop scan for the same URL track changes independently. A visual change on desktop does not affect your mobile baseline.

Different regions: create separate scans for each region. A scan set to United States and a scan set to France each track their own baseline independently.

Staging and production: create one scan for each environment and track them independently. Or use a Compare Environments scan, which crawls both environments fresh on every run and shows you a live diff between the two. No baseline is saved. Every run is a direct comparison of what exists in each environment at that moment.

Naming your scans clearly makes this easier to manage. Use descriptive names that include the configuration, for example “Desktop - Main Site”, “Mobile - Main Site”, or “Staging - US”. This way you can find and re-run the right scan quickly without guessing.

Each scan runs independently. Updating the baseline on your desktop scan does not affect your mobile scan.

The baseline never updates automatically

Section titled “The baseline never updates automatically”

The baseline only changes when you explicitly click Set as Baseline. It never updates on its own.

This means you can re-run a scan multiple times without losing your reference point. Every run compares against the same baseline until you choose to update it.

This is by design. Make changes, re-run, review, fix issues, and re-run again, all while comparing against the same known-good state.

What to do next

Section titled “What to do next”