Five Years of Google Core Updates and What Mueller Just Revealed About How They Actually Roll Out

Google’s John Mueller responded to a question on Bluesky on March 31, 2026, about whether core updates roll out in stages or follow a fixed sequence. The answer he gave is one of the clearest explanations of how core updates actually work that Google has shared publicly, and it reframes how the SEO industry should think about the volatility waves that show up during every rollout.

Mueller’s response: “We generally don’t announce ‘stages’ of core updates. Since these are significant, broad changes to our search algorithms and systems, sometimes they have to work step-by-step, rather than all at one time. (It’s also why they can take a while to be fully live.)”

He followed up with a second post that went further: “I guess in short there’s not a single ‘core update machine’ that’s clicked on (every update has the same flow), but rather we make the changes based on what the teams have been working on, and those systems & components can change from time to time.”

Two things stand out from that exchange. First, core updates are not a single switch being flipped. They’re a collection of changes across multiple systems, deployed incrementally. Second, the composition of a core update varies from one release to the next. The systems and components involved aren’t fixed. Different teams contribute different changes depending on what they’ve been working on, which means no two core updates are structurally identical even if they carry the same “core update” label.

That context makes the last five years of core update history easier to read. The variation in rollout duration, in which industries get hit, and in how recovery behaves across different updates all make more sense when the update itself is understood as a variable collection of component changes rather than a single algorithmic adjustment.

The Core Update Timeline: 2021 to 2026

Google has released 17 core updates since June 2021. The pace has been fairly consistent at three to four per year, though the character of these updates has shifted significantly over time.

2021 saw three core updates. June (June 2 to June 12), July (July 1 to July 12), and November (November 17 to November 30). The June and July updates were unusual because Google explicitly announced them as two parts of a broader change, with the July update completing work that began in June. Rollouts were relatively short, ranging from 10 to 14 days. The updates focused primarily on content relevance and quality signals as Google continued refining the systems that had been in development since the 2019 BERT update.

2022 brought two core updates. May (May 25 to June 9) and September (September 12 to September 26). But 2022’s bigger story was the launch of the Helpful Content Update in August, which introduced a site-wide signal designed to penalize content created primarily for search engine rankings rather than human readers. The Helpful Content system operated as a separate signal from the core algorithm, applying a domain-level penalty that could drag down rankings for an entire site if a significant portion of its content was deemed unhelpful. A second Helpful Content Update followed in December 2022.

2023 was Google’s busiest year for core updates, with three: March (March 15 to March 28), August (August 22 to September 7), and October (October 5 to October 19), plus a November core update (November 2 to November 28) that ran nearly four weeks. The September 2023 Helpful Content Update hit particularly hard and became one of the most discussed updates in recent SEO history. Many sites that lost visibility in September 2023 spent the next year waiting for recovery that, in some cases, never came. Affiliate sites, product review sites, and content-heavy publishers were the most affected categories.

2024 started with the March 2024 core update, which turned out to be the most significant algorithmic change in years. It ran for 45 days, the longest core update rollout on record, and it did two things that changed the landscape permanently. First, Google absorbed the Helpful Content system into the core algorithm. The separate signal that had been running since August 2022 was folded into how Google evaluates every query, which meant helpfulness assessment shifted from a standalone system to a component of core ranking. Second, Google moved from site-level helpfulness evaluation to page-level evaluation, using a combination of signals rather than a single sitewide penalty score. Google’s stated goal was to reduce low-quality, unoriginal content in search results by 40%. Three new spam policies launched simultaneously: expired domain abuse, scaled content abuse, and site reputation abuse. The August update (August 15 to September 3) and two more core updates in November (November 11 to December 5) and December (December 12 to December 18) followed. The December update was notable for its speed, completing in just six days.

2025 brought three core updates and marked the year where AI-related content quality became a central focus. The March update (March 13 to March 27) put continued pressure on AI-generated content that lacked original analysis or first-hand experience. The June update (June 30 to July 17) appeared to weigh off-page factors more heavily, with link quality, brand authority, and topical relevance of referring domains playing a larger role. More than 50% of sites that had been affected by the September 2023 Helpful Content Update saw improvements during the June 2025 update, suggesting that the page-level evaluation introduced in March 2024 was finally catching up to sites that had fixed their content quality issues. The December update (December 11 to December 29) expanded E-E-A-T requirements beyond traditional YMYL categories into virtually all competitive queries.

2026 has already seen the February Discover core update (the first core update specific to the Discover feed rather than general search), the March 2026 spam update, and the March 2026 core update, which began rolling out on March 27.

What Changed Between 2021 and 2026

Looking at five years of updates in sequence, a few shifts stand out.

The Helpful Content integration was the single biggest structural change. What started as a separate system in August 2022 became part of core ranking in March 2024, and the shift from site-level to page-level evaluation changed how recovery works. Before March 2024, a site penalized by the Helpful Content signal needed to improve its overall content quality across the domain. After March 2024, individual pages are evaluated independently, which means a site can have some pages performing well while others are still suppressed.

The pace of updates has stayed consistent, but the composition has become more complex. Mueller’s Bluesky explanation confirms what practitioners have observed: each core update touches different systems depending on what Google’s teams have been working on. The March 2024 update took 45 days because it combined multiple major changes (Helpful Content integration, page-level evaluation, new spam policies). The December 2024 update completed in six days, likely because it involved fewer component changes. Rollout duration is a rough proxy for how many systems are being updated simultaneously.

Recovery patterns have become more gradual. In the earlier core updates (2021-2022), ranking changes tended to settle within the rollout period. In recent updates, particularly after the March 2024 changes, recovery from previous updates has appeared in later core updates rather than within the same cycle. Google has stated that some changes may take months to be reassessed, and some effects require waiting for the next update cycle.

Off-page signals have gained weight over time. The June 2025 core update was notable for how heavily link quality, brand authority, and referring domain relevance appeared to influence outcomes. Combined with the growing role of backlink profiles in AI citation data (SE Ranking found that sites with 32,000+ referring domains are 3.5x more likely to be cited by ChatGPT), the signal is consistent: link building from relevant, authoritative sources feeds both traditional search rankings and the newer AI visibility layer.

Mueller’s Explanation and What It Means for Reading Core Updates

Mueller’s description of core updates as collections of team-driven component changes rather than a single algorithmic switch explains several patterns that have puzzled practitioners.

It explains why volatility during a rollout comes in waves rather than all at once. If different components go live at different points during the rollout window, rankings can shift, settle, shift again, and settle again as each component takes effect. The waves of volatility that practitioners observe during the typical 2-3 week rollout period likely correspond to different system components going live at different times.

It explains why different industries get affected at different points during the same update. If one component targets content quality signals and another targets link evaluation, the industry impacts won’t be simultaneous. Sites heavily dependent on link signals might see movement early while content-driven shifts appear later, or vice versa, depending on when each component deploys.

It explains why recovery sometimes happens mid-rollout. If a site was suppressed by a component that goes live early in the rollout, and a later component reevaluates the same signals more favorably, the site could see partial recovery before the update officially completes.

And it explains why Google says to wait until the rollout is fully complete before drawing conclusions. If the update is a sequence of component deployments rather than a single change, any assessment made mid-rollout is based on an incomplete picture. The final state after all components have deployed may look different from the state at any individual point during the rollout.

What to Do During and After a Core Update

The guidance hasn’t changed much over five years, which is itself informative: the principles Google rewards have been consistent even as the systems evaluating them have evolved.

Focus on content quality, depth, originality, and demonstrated expertise. The Helpful Content integration into core ranking made these signals central to how Google evaluates every page. Content created primarily to rank rather than to genuinely help users has been consistently penalized across every major update since 2022.

Build authority through editorial relationships and earned coverage. The increasing weight of off-page signals in recent core updates, combined with the growing importance of third-party presence for AI visibility, makes digital PR and guest posting on relevant industry publications a dual-purpose investment that serves both traditional rankings and AI citation systems.

Don’t make reactive changes during a rollout. Mueller’s explanation confirms that the ranking state mid-rollout is incomplete. Wait for the rollout to finish, then evaluate whether changes are needed based on the settled state rather than the intermediate fluctuations.

Track performance across update cycles, not just within them. Recovery from one core update may appear in a subsequent core update months later. A site that lost visibility in March may not see recovery until June or later, and that timeline is normal rather than a sign of permanent penalty.

And monitor what Google communicates about each update. Google doesn’t always disclose what a core update targets, but when they do provide guidance (as they did extensively with the March 2024 update), that guidance tends to remain relevant across subsequent updates in the same evolutionary direction.