A core update is a significant, broad change to the main systems Google uses to rank search results. Google releases several each year, announces them publicly, and describes them as changes to how it assesses content overall rather than as action against any particular site or practice.
How a core update works
Google changes its search algorithm constantly in small ways that nobody announces. Core updates are different in scale. They adjust how the many signals Google uses are weighed against one another, so the whole picture of which pages best answer which searches is redrawn at once.
Google posts each one on its Search Status Dashboard with a start date, and the rollout usually takes around two weeks. During that period rankings can swing from day to day before settling, which is why the end of the rollout is the earliest sensible point to assess the effect.
A few points about how they behave are worth knowing:
- They are not penalties. A drop means other pages were judged more useful for those searches, not that your site broke a rule. Rule-breaking is handled by spam systems and by a manual action, which appears in Search Console.
- They work at page and site level. One section of a site can fall while another rises.
- Since 2024 they absorb the old helpful content signals. Google folded its helpful content system into its core ranking systems, so “is this written for people or for search engines?” is now part of every core assessment.
Why it matters
For a UK business that relies on organic search for enquiries, a core update can move visibility noticeably within a fortnight in either direction. A plumbing firm in Bristol might see its service pages hold steady while thin “plumber in [every suburb]” pages lose ground. An ecommerce site might find its category pages strengthened and its copied manufacturer descriptions weakened.
Core updates also expose how much a site’s visibility depends on borrowed strength. Pages that ranked because the competition was weak, not because they were genuinely good, are the ones most exposed when Google gets better at telling the difference.
Common mistakes
- Reacting mid-rollout. Rewriting pages or changing titles while rankings are still moving makes it impossible to tell what caused what.
- Looking for a single technical fix. Google has said there is usually nothing specific to “fix”. Broken canonicals will not explain a core update drop on their own.
- Blaming the update for every dip. Seasonality, a lost link, a tracking error or a site change in the same week can look identical in a traffic graph.
- Deleting content in a panic. Removing pages without assessing them can throw away the ones that were still earning traffic.
- Expecting instant recovery. Improvements are often only fully reflected after a later core update, months away.
How to act on it
Wait for Google to confirm the rollout has finished, then compare a period after it with an equivalent period before it in Search Console. Look at which pages and which queries moved, not just total clicks. Check whether the losses cluster in one template or section, and look at who now ranks in your place: their pages tell you what Google currently rewards for those searches.
Then assess the affected pages honestly. Ask whether they show first-hand experience and real expertise, the qualities described as E-E-A-T, whether they answer the question better than the pages now above them, and whether they exist mainly to rank. Improve or merge what falls short, and keep a dated log of changes so you can judge them later. If you want an outside view on why a section dropped and what to change first, that diagnosis is part of an SEO audit.