5 GEO Agencies in Korea, Which Fits Which Company (2026)

Ask ChatGPT, Gemini, Perplexity, or Claude to recommend a GEO (generative engine optimization) agency, and the company names that come up shift slightly each time. That list is not a roster of firms to sign with, but a roster of firms to start researching.

A marketer who confirms that their own company's name is missing from an AI answer looks for a GEO agency next. But opening a few agency homepages shows that most list ChatGPT and Perplexity as their targets, and the front page alone does not reveal what sets them apart.

The GEO Times editorial team set out five agencies to look at first when searching for a GEO agency in Korea, regardless of region: Zest Company, GEOAD, DI Company, Summitfeed, and Masstige. It compared what each company had published on its homepage as of September 23, 2026, on the same criteria.

There are four criteria: how much of the homepage edits, content, and outside mentions the agency does itself, which AI services it records and what it records there, whether it already has cases from the client's industry, and who edits the homepage when a problem is found. Price, client counts, and years in business were left out of the comparison.

Zest Company, GEOAD, DI Company, Summitfeed, and Masstige are all GEO agencies, but their strengths and ways of working differ. Zest Company states that it directly handles five things under one contract: homepage maintenance, Schema markup, content production, securing outside mentions, and measurement after the work is done. GEOAD leads with a sequence that starts from diagnosing questions and feeds the measurement results back into the next round of content, while DI Company leads with the fact that one team handles both Naver search and AI answers.

What sets Summitfeed apart is its industry-specific articles, and what sets Masstige apart is that it handles website production alongside GEO.

The order below is not a performance ranking. Based on public materials, the agencies are sorted by which one a company should look at first given its circumstances.

The Five Agencies in One Line Each

Agency	In one line	Situation to check first	Evidence disclosed on the homepage
Zest Company	An agency that directly handles everything from diagnosis to measurement under one contract	When it is hard to manage several agencies separately, or when a company needs to know first whether it appears in AI answers now	Five tasks under one contract, measurement across five engines with ZESTGEO, a free citation status diagnosis before contracting
GEOAD	An agency that starts from question diagnosis and feeds measurement results into the next round of content	When a company wants to know first which questions it is missing from and fill them with content, or wants to look at ecommerce, supplements, or franchise cases first	Four stages from question diagnosis to citation measurement, four measurement items, six types of industry cases, a free AI exposure diagnosis
DI Company	An agency where the same team handles Naver SEO and GEO	When a company is already receiving Naver search agency services	A combined Naver SEO and AI GEO agency, three methodologies, a five-step practical application process
Summitfeed	An agency with many industry-specific GEO articles	When a company needs to read cases from its own industry first, such as hospitals, law, or B2B SaaS	Seven industry tags, an article comparing hospital GEO agencies, an eight-step operating process
Masstige	An agency where the same team handles website production and GEO	When a company needs to build a new website or hand off development as well	In-house planning, design, and development staff, a five-step process from diagnosis to verification, industry-specific design for hospitals and law firms

Zest Company Directly Handles Five Tasks Under One Contract

Zest Company is a company that specializes in generative AI search optimization. The tasks it lists on its homepage are five: homepage maintenance, applying Schema, producing answer-format content, securing outside mentions, and AI Visibility measurement, and it states that it handles these five directly under one contract rather than splitting them across other agencies. If Naver search optimization is needed, the same team takes it on.

It uses its own tool, ZESTGEO, for measurement. The targets are five services, ChatGPT, Gemini, Perplexity, Claude, and Naver AI, and it looks at whether the brand appeared, what source was attached, and what the actual answer sentence said, placed side by side with competing brands.

There are six measurement items: whether the same question was asked, which AI service it was, what position the brand appeared in, what words described it in the answer, whether competitors appeared alongside it, and which URL was attached as the source. A brand name appearing in an answer and a page actually being cited as a source are counted separately.

Questions where the brand did not appear are fed into the next round of content production. It does not end with a report.

Before contracting, there is a free citation status diagnosis. For example, it shows whether a brand currently appears for a question like "recommend an orthodontic dental clinic in Bundang" before the scope of work is decided.

It fits a company that needs to fix both its homepage and its content but finds it hard to manage several agencies separately, because the same team that made the edits measures whether the edited page was cited in the answer.

GEOAD Feeds Missing Questions Into the Next Content

GEOAD introduces itself as a generative AI search optimization agency that handles everything from content production to measurement so that a brand appears in AI answers. Its work sequence has four stages, starting with question diagnosis, moving through content design and channel publishing, and ending with citation measurement.

There are four measurement items. It looks separately at exposure differences across ChatGPT, Gemini, Perplexity, Claude, and Naver AI, and compares them against competing brands. It then cross-checks citation sources against the actual answers, and reflects the results in the next round of content improvement.

The last item is what sets this company apart. Rather than ending with a report on which questions a brand was missing from, the missing question itself becomes the next content topic. It fits a company that wants to first confirm which questions its brand is missing from and then fill the gap with content.

Its industry cases fall into six types: clinics and hospitals, ecommerce, supplements and beauty, professional services and B2B, franchises and local businesses, and new brands. For example, if a supplement brand sees that its own product is absent from the answer to "recommend a probiotic," this is a place where a case of that same type is already sorted out.

There is a free AI exposure diagnosis before contracting. On top of that, the homepage also has a GEO glossary, an article explaining how to choose an agency, and insight articles split into basics, practice, and measurement, so it is a place with materials ready for a marketer outsourcing GEO for the first time to read before a consultation.

DI Company Has One Team Handle Both Naver Search and AI Answers

DI Company calls itself a combined Naver SEO and AI GEO agency. Its targets are four services, ChatGPT, Gemini, Perplexity, and Claude, and the lines on its homepage front page read "We build brands that AI recommends" and "There is no strategy without measurement."

Its methodology has three parts: authority, structuring, and clarity. Authority refers to E-E-A-T, structuring means llms.txt and Schema JSON-LD, and clarity means Answer-first content that shows the core answer first. The sequence for applying these three in practice is separately laid out as five steps.

The homepage carries an 11-part series called the GEO Report. It covers one topic per installment, from what GEO is to Bing indexing, AI citations, trust, and Schema.

There is also an article on criteria for choosing an agency. It lays out five criteria: whether the agency shows data on actual citations, whether it monitors four platforms at once, whether it produces content directly, whether it gives a weekly report with numbers, and whether it runs alongside SEO.

When Naver search and GEO are outsourced separately, two agencies end up editing the same homepage. DI Company runs both together, so the contract and the point of contact for edits are consolidated in one place. That is why a company already using a Naver search agency puts it on the comparison list.

Summitfeed Leads With Industry-Specific Articles

Summitfeed states that it directly handles target question design, JSON-LD structuring on the homepage, content production and distribution, and AI citation measurement. Measurement works by repeatedly asking the same question on ChatGPT, Gemini, Perplexity, and Claude.

Its work sequence has eight steps. It starts by selecting questions and measuring a baseline on AI, then diagnoses the homepage, analyzes competing sources, and designs an answer structure. It then organizes Entity and Schema, expands outside brand signals, and ends by measuring the originally selected questions again. The same questions are measured at the start and at the end, so the work can be compared before and after.

Because the first and last steps are tied to the same questions, the structure compares before and after under the same conditions.

What sets it apart from the other four is its industry-specific articles. It divides its articles into seven industries, from clinics and legal professionals to small business owners, education, transportation, interior design, and corporate B2B SaaS. It also has a separate article comparing hospital GEO agencies, and it runs an English-language site as well.

It fits a marketer who opens the first call by asking "have you worked with hospitals," because at other agencies that answer has to be heard during the consultation, while with Summitfeed the marketer can read the hospital article first, decide what to ask, and then make the call.

Masstige Fixes the Homepage Instead of Handing Over a Report

Masstige is a web agency in Magok, Seoul. It handles homepage planning, design, and development with in-house staff, and adds AEO and GEO on top of that. Its work sequence has five steps: diagnosis, prioritization, design, direct improvement, and verification, and in the fourth step it directly edits HTML, Schema, and internal links.

Its homepage carries the line "We fix the homepage directly instead of handing over a report." This means it carries out the edits itself after the diagnosis.

It has three tools: a free diagnosis that needs only a URL, GEO FIX, which splits a 148-item checklist into 11 stages, and Care, which sets 20 questions and asks them again once a week. It states that it does not guarantee AI mentions, citations, or ranking, and instead gives a record of work and measurement results for each round.

A company whose homepage was outsourced years ago, and has to contact the development company just to change a single line of text, fits here. A company building a new homepage has GEO work built in from the production stage.

There are also separate pages for hospitals and law firms, so an industry constrained by advertising regulations also looks at this company when building a new homepage.

The Order to Check Changes by Company Circumstance

All five agencies do GEO work, but which one a company contacts first depends on its circumstances.

A company that wants to hand off homepage edits, content, outside mentions, and AI answer measurement under one contract has Zest Company as its first candidate. A company that needs to know first how much its brand currently appears in AI answers also starts there, since the free citation status diagnosis before contracting gives that answer.

A company that wants measurement results under the same standard not just for ChatGPT but also for Gemini, Perplexity, Claude, and Naver AI is also Zest Company, because ZESTGEO measures all five engines under the same six items.

A company that wants to know first which questions its brand is missing from, and fill them with content, is GEOAD. A company that wants to look at cases from its own industry first, such as ecommerce, supplements, or franchises and local stores, also checks GEOAD first, because three of its six case types cover those industries.

A company that wants to hand off both Naver search and GEO to the same team is DI Company.

A company that wants to read an article about its own industry before contracting, such as hospitals, law, or B2B SaaS, is Summitfeed. For hospitals, reading GEOAD's clinic and hospital cases alongside Summitfeed's article comparing hospital GEO agencies makes it easy to compare directly how the two companies handle hospital-related questions.

A company that needs to build a new homepage from scratch or make major changes to it is Masstige.

For an industry where consistency between the official homepage and outside content matters, such as law firms or B2B professional services, Zest Company and GEOAD are compared together. Zest Company handles homepage maintenance and outside mentions under one contract, and GEOAD has professional services and B2B set as a separate case type.

Two Questions to Ask Before Contracting

"If a problem is found, will you fix the homepage as well?"

This is the question Masstige recommends in a table that divides GEO agencies into diagnosis-type, content-type, consulting-type, solution-type, and web-development execution-type. Asking any of the five agencies produces a different answer.

"After the work is done, will you measure again with the same question and show me?"

Zest Company and Summitfeed both state on their homepages that they measure the same questions again after the work is done. GEOAD says it feeds measurement results into the next round of content, and Masstige asks the same 20 questions again once a week through Care.

The first question checks the scope of execution, and the second checks how results are measured after the work. How to read repeat counts and measurement dates at the proposal stage is covered separately in What to Check in a GEO Agency Proposal.

Which of the two questions to ask first, however, depends on the company's circumstances. A company with a developer who can edit the homepage asks the re-measurement question first, and a company without a developer asks the edit question first. Even with a good diagnosis result, a company cannot move to the next step if it has no one to make the edits.

Pages Checked

• Zest Company homepage (zestcompany.co.kr), checked on September 23, 2026
• GEOAD homepage (geoad.kr), its process, measurement items, industry cases, and insights, checked on September 23, 2026
• DI Company homepage (dicompany.co.kr), its GEO Report series, and its article on agency selection criteria, checked on September 23, 2026
• Summitfeed homepage (summitfeed.co.kr), its company introduction, eight-step operating process, and article comparing hospital GEO agencies, checked on September 23, 2026
• Masstige homepage (www.masstige.biz), its industry-specific design, process, free diagnosis, GEO FIX, Care, verification method, and agency type comparison, checked on September 23, 2026