Monthly AI Search Industry Report, April 2026: Core Update and Search Ranking Fluctuations - AI Search Usage Expands Approximately 3.5 Times in 8 Months

The AI search and SEO industry in April 2026 marked a pivotal turning point, characterized by two major shifts: the lingering effects of Google's core update, which began on March 27, and the dramatic surge in AI search usage. This report organizes the key updates, domestic and international research results, and public data related to changes in search behavior observed during the month.

Post-rollout re-fluctuations, declining click-through rates for informational queries, and a 3.5-fold increase in AI search usage – these are not isolated phenomena but must be understood as part of a single overarching trend: the shift in evaluation metrics from "ranking high in search" to "being cited by AI."

From various data and industry trends in April, it is evident that the focus of evaluation metrics is shifting from traditional SEO's "measures to improve search rankings" to "building information assets that are cited and recommended by AI" in the era of AI search.

*What is a Core Update: Refers to a major overhaul of Google's core search algorithm aimed at improving the overall quality of search results. Typically performed 2-4 times a year, it is pre-announced on the Google Search Central blog. For example, the March 2026 Core Update rolled out from March 27 to April 8, 2026, and has been completed.

SECTION 01 ─ Important Updates This Month

Post-Rollout Re-fluctuations Indicate Continuous Adjustment of Evaluation Metrics

Google's March 2026 Core Update, which began on March 27, 2026, completed its rollout on April 8 after approximately 12 days. Usually, a period of ranking stability follows the completion of a core update, but this time, large-scale ranking fluctuations have been observed again since around April 23, approximately two weeks after completion.

Similar reports have been pouring in from overseas SEO communities, including Search Engine Roundtable, and are being analyzed as either a precursor to the next update or a continuous adjustment of evaluation criteria.

Compared to past cases, the scale of this rollout was reported to be more limited than the large-scale update implemented in December 2025. However, the continuous fluctuations after completion suggest the limits of short-term ranking measures, making the discussion about adapting to a shift in evaluation metrics itself a key point.

▼ POINT

A month characterized by continuous adjustment of evaluation criteria. The focus going forward will be on reviewing site structure based on the premise of a shift in evaluation metrics, rather than individual responses to short-term ranking fluctuations.

SECTION 02 ─ Official Google Announcements

Spam Policy Updates and New Feature Trends

In April 2026, Google announced updates to its spam policy. Methods that were previously not explicitly defined and considered "gray areas" will now be formally defined as violations. The main focus of this update is to strengthen measures against designs that impair user experience.

The implementations targeted may be unintentionally incorporated when site production is outsourced, so it is recommended to review corporate site designs before the policy takes effect on June 15.

Meanwhile, the implementation of new Search Console features (such as brand query filters) has been delayed. This suggests that Google itself may be coordinating integration with AI search.

On the other hand, the Chrome version of Gemini has added a Skills feature, allowing frequently used prompts to be saved and reused. This transition means that search is moving from single-query input to an interactive, mutual-understanding experience.

▼ POINT

Google's direction is consistently incorporating genuine response to user behavior into its evaluation criteria. More than technical optimization, UX design itself is becoming a subject of evaluation.

SECTION 03 ─ AI Search Trends

Changes in Click Behavior and Usage Rates

As of April 2026, there is a pronounced trend where higher search rankings do not necessarily correlate with increased traffic to a site. This is because AI Overviews (AI-generated summaries) displayed at the top of Google search results allow users to obtain necessary information without visiting individual sites.

The impact is particularly noticeable for informational queries (Know queries). In some industries, there have been reports of a 40% decrease in click-through rates for the #1 search result.

Meanwhile, ChatGPT and Perplexity...