Change Tracking: What to Look At After a Re-Crawl

Published 2026-08-01 · 6 min read · by the isaeo team

Why the diff beats the snapshot

A single crawl tells you the state of a site. It cannot tell you whether that state is an improvement, a regression, or exactly what it was last month. For ongoing work, the comparison carries nearly all the information.

It also solves the verification problem. You told a client to add meta descriptions to 40 pages. Did they? A snapshot says "38 pages missing meta descriptions" — is that better? A diff says "2 resolved, 38 still missing", and now you know the answer.

The six things to check

• Health score delta. The headline. A drop of 5+ points warrants investigation; 15+ is an incident.
• AEO score delta. Often moves independently — a template that drops structured data can leave the SEO score untouched while AEO falls.
• New issues. Issues present now that weren't before. Cluster them — 40 new issues on 40 pages is usually one template change, not 40 problems.
• Resolved issues. Proof the work shipped. Also the section clients most want to see.
• Pages added or removed. Unexpected removals mean broken internal links, a failed deploy, or content pulled without anyone mentioning it.
• Per-page field changes. A title, meta description, canonical or robots tag that changed or vanished on a specific URL.

Red flags

Some diffs deserve an immediate message rather than a note in next month's report:

• A canonical tag disappearing sitewide. Almost always a template regression, and it splits duplicate-URL signals immediately.
• A robots meta appearing. An accidental noindex is the highest-cost single fault in SEO — it removes pages from search entirely.
• Many pages removed at once. Either a deploy failure or a content decision nobody told you about.
• Titles changing en masse. Sometimes intentional, often a CMS upgrade rewriting them badly.
• A score dropping with no new issues. Usually means thin new pages diluting the average — see thin content.

Getting the cadence right

Match crawl frequency to change frequency. A brochure site that changes twice a year does not need weekly crawls; a publisher shipping daily does.

The useful rule: crawl often enough that a regression is caught before it compounds, and rarely enough that you actually read the results. A weekly diff nobody opens is worth less than a monthly one that gets reviewed properly.

Automating this is what makes it stick — see the monthly workflow. isaeo diffs every crawl against the previous one automatically, shows new and resolved issues as chips on the site page, and can email you when a scheduled crawl finds the site down, the score dropped sharply, or meta tags went missing.

For choosing the interval itself, see how often to crawl your own site. And the one case where daily crawling genuinely earns its keep is the fortnight after a move — the migration checklist covers what to watch.