AI Search Engines Compared 2026: ChatGPT, Google AI Mode, Perplexity, Gemini and Naver

Key takeaway: AI search engines differ in when they search the web, how they show sources and which model they give free users. Perplexity searches the web for nearly every question, ChatGPT and Gemini decide per question whether to search, and Google AI Mode and Naver AI Briefing answer on top of their own search results. In September 2026, ChatGPT had 24.7 million app users in Korea, Gemini 9.87 million and Perplexity 1.29 million. When RanketAI measured 12 Korean B2B SaaS companies on the same day, all three engines mentioned 83% of the brands, but the share citing the brand's own site as a source was 83%, 33% and 67% depending on the engine.

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Three-line summary

• How they search: Perplexity always searches the web; ChatGPT and Gemini search only when needed. Google AI Mode and Naver AI Briefing build on their own search results.
• Scale in Korea: by September 2026 app users, ChatGPT leads with 24.7 million, while Naver AI Briefing is a surface at the top of Naver results used by about 30 million people a month.
• For brands: engines cite different types of sources for the same question, so results from one engine cannot stand in for another.

Five AI search engines compared (October 2026)

The clearest differences between AI search engines lie less in answer quality than in when they run a web search and how they show sources.

Engine	Web search	Source display	Free default model	Usage in Korea
ChatGPT search	Per question (14.4% of free, logged-out responses)	Links in the answer and a source list	GPT-6 Luna	24.7M monthly app users (2026-09)
Google AI Mode	Built on Google Search; splits a question into several sub-searches	Inline links and links at the end	Not publicly specified	No public figure (Korean launch 2025-09)
Perplexity	For nearly every question	Numbered sources	Best, automatic	1.29M monthly app users (2026-09)
Gemini app	Uses Google Search per question	Some answers have no sources	Auto (mostly Flash-Lite)	9.87M monthly app users (2026-09)
Naver AI Briefing and AI Tab	Built on Naver search results	Source cards	Not applicable	AI Briefing ~30M monthly; AI Tab 10M+ users

Korean app user counts are from Wiseapp·Retail's September 2026 survey. Free default models follow each company's announcements; details are in Which Model Do Free ChatGPT, Gemini and Perplexity Use?. Naver figures are July reports collected in The Korean AI Search Landscape 2026.

ChatGPT is the most used AI app in Korea (September 2026)

In September 2026, ChatGPT had 24.7 million monthly app users in Korea, about 2.5 times the 9.87 million of second-place Gemini.

Rank	App	Monthly users
1	ChatGPT	24.7M
2	Google Gemini	9.87M
3	Claude	4.04M
4	Microsoft Copilot	1.96M
5	Grok AI	1.29M
5	Perplexity	1.29M
7	A. (SK Telecom)	1.10M

Source: ZDNet Korea (2026-10-13, Wiseapp·Retail survey)

In the same survey, deduplicated users of the top ten apps grew 19% in a year, from 25.93 million to 30.75 million, and total usage time rose 64%, from 2.8 billion to 4.6 billion minutes. The survey counts dedicated mobile apps only, so people who use AI only in a web browser are not included.

Figures vary widely by tracker. Mobile Index counted 17.99 million ChatGPT users in Korea for the same September and 590,000 for Perplexity, down 29.1% from a year earlier (Money Today, 2026-10-06). Compare rankings and trends within one tracker rather than mixing the two.

ChatGPT search decides per question whether to search the web

ChatGPT does not search the web for every question; of free, logged-out responses from August to September 2026, 14.4% ran a web search.

That figure comes from Ahrefs' analysis of 66.6 million free, logged-out ChatGPT responses (Ahrefs, 2026-10-12). The rest were answered from what the model learned in training. When it does search, ChatGPT splits the question into several queries, and 6.8% of those fan-out queries used the site: operator to look up a specific site directly.

Regular Chat for free users has been answered by GPT-6 Luna since October 8, 2026. Korea, together with Japan, is the first Asian market where ChatGPT ads run, and ads are shown only to Free and Go users (ChatGPT Ads Land in Korea).

Good for: exploring a topic through conversation, or searching and then writing or summarizing in the same window.

Google AI Mode and AI Overviews answer on top of Google Search

Google AI Mode is a conversational search tab, AI Overviews is the AI summary at the top of regular results, and both answer from Google Search results.

AI Mode launched in Korean on September 9, 2025, and can be used from the AI Mode tab in Google Search without signing up (Byline Network). How it splits one question into several sub-searches before answering is covered in the query fan-out analysis.

On October 15, 2026, Google announced changes to how links appear in AI Mode and AI Overviews. According to reporting, inline links will appear higher and more often, related links at the end will get image thumbnails, and Google is testing a section at the top that shows the one or two official pages needed to complete a specific task (9to5Google).

AI Overviews are also spreading to brand-name searches. On US desktop, the share of branded keywords showing an AI Overview rose from a July average of 61.3% to a September average of 73.3%, and reached 82.91% on September 29 (Ahrefs, 2026-10-02). Whether Korean search shows the same pattern has not been confirmed.

Good for: asking longer versions of questions you would normally type into Google, or moving straight to links in the results. AI Mode's effect on clicks is covered in the 1,100-user field experiment.

Perplexity searches the web for nearly every question

Perplexity runs a web search for each question and answers with numbered sources, which makes the evidence behind an answer easy to check in the original.

When RanketAI observed Perplexity's answer stream, it did not skip search on any of seven queries, and it looked up the web even on a question ChatGPT answered from memory (Perplexity Never Skips the Web). The number of queries observed is small, so this is not generalized as a rate.

On the free plan, Best automatically picks a model for each question, and advanced Search models cannot be chosen manually (Perplexity Help Center). Perplexity had 1.29 million Korean app users in September 2026 (Wiseapp·Retail), about 5% of ChatGPT's, and Mobile Index shows a 29.1% decline over the year.

Good for: checking recent information with sources, or research that compares several references.

Gemini sometimes answers without sources

The Gemini app uses Google Search depending on the question, but not every answer includes sources, so check first whether a Sources button is present.

Google's help center says:

"Not all responses include related links or sources. If you don't have the Sources button below a response, Gemini Apps didn't provide any links for that particular response." — Google, Gemini Apps Help

In RanketAI's October 2026 measurement with web search enabled, every ChatGPT and Perplexity answer ran a search, while only 38% of Gemini answers did (October 2026 benchmark analysis). These are results under measurement conditions rather than app screens, so the rate in the app may differ.

Since October 9, 2026, users without a plan default to Auto model selection, and Google says most prompts go to Flash-Lite (Gemini Apps Help). The top model, Gemini 4 Argon, is for Google AI Pro and Ultra subscribers.

Good for: working alongside Gmail, Docs and other Google services, or tasks such as summarizing long text and organizing ideas where search is not essential.

Naver AI Briefing and AI Tab answer from Korean search results

Naver AI Briefing is the AI summary at the top of Naver search results, and AI Tab is a separate screen for asking follow-up questions in conversation.

As of June 2026, AI Briefing appeared on about 27% of all search queries, with a plan to reach about 40% by year-end (Electronic Times). It was reported to have about 30 million monthly users. The conversational AI Tab launched to all users on June 26, 2026 and passed 10 million users by mid-July (Byline Network). Ads (AdBoost) began appearing in AI Briefing on July 21.

Naver AI Briefing draws heavily on content inside Naver, such as blogs and cafés. Its citation structure is covered in What Naver AI Briefing Cites.

Good for: local places, shopping and everyday information in Korea, where Naver blogs and cafés hold a lot of content.

Engines cite different sources for the same question

Measured on the same day, engines differ in how often they search and which sources they cite, so one engine's result cannot stand in for another's.

RanketAI measured 12 Korean B2B SaaS companies three times each with ChatGPT, Gemini and Perplexity on October 16, 2026 (October 2026 benchmark).

Engine	Brand mention rate	Own-domain citation rate	Answers that ran a web search
ChatGPT	83%	83%	100%
Perplexity	83%	67%	100%
Gemini	83%	33%	38%

Mention rates were identical, but the share citing the brand's own site differed 2.5-fold. The top sources in answers that searched also differed: ChatGPT leaned on official product sites, Perplexity on comparison and catalog sites plus blogs and media, and Gemini on official product sites and blogs. The sample is weighted toward well-known brands, so the size of these rates is not generalized.

If you manage a brand, check each engine separately. How to check by hand is covered in How to Check If ChatGPT Mentions Your Brand: 5 Steps. RanketAI's AI brand visibility analysis measures ChatGPT, Gemini and Perplexity answers under the same conditions; Google AI Mode and Naver AI Briefing are not in its scope.

FAQ

Related reading

• Which Model Do Free ChatGPT, Gemini and Perplexity Use? — free and paid models by engine.
• The Korean AI Search Landscape 2026 — how Naver and global LLMs overlap in Korea.
• 62% of Gemini Answers Came Without a Web Search — Korean SaaS Benchmark — the original analysis of search rates and source types by engine.
• The Source Gap — finding the third-party sources that differ by engine.

Update basis

• First written: 2026-04-05 (three-way comparison of ChatGPT Search, Google AI Mode and Perplexity)
• Full update: 2026-10-23 (five engines; usage in Korea, web search behavior and free default models added)
• Next scheduled review: 2026-11-23