Vietnamese SEO: Cốc Cốc, Diacritics and Keyword Research

Strip the marks from má, mà, mả, mã and mạ and all five turn into ma, the Vietnamese word for ghost. The five words mean mother, but, grave, horse and young rice stalk. Vietnamese has six tones and five tone marks, per Michigan State University's Basic Vietnamese course, so a query typed without them leaves the search engine to guess the word.

How much does Cốc Cốc matter next to Google in Vietnam?

Cốc Cốc's desktop share in Vietnam swings by several points within a year: it was 11.71% in November 2024 and 5.72% in July 2026. In August 2026, StatCounter's desktop search engine data for Vietnam put it at 7.15%, against 90.29% for Google and 1.58% for Bing. On mobile the same month, Cốc Cốc fell to 3.49% and Google rose to 96.30%.

StatCounter counts search engine referrals: clicks from a results page to one of the sites running its tracking code. It does not count searches, so a query that ends without a click leaves no trace.

The two devices are moving in opposite directions. Cốc Cốc's yearly desktop share peaked at 10.15% in 2021, its best full year in StatCounter's data, and stood at 7.2% for January to August 2026. Its mobile share climbed from 1.71% to 3.47% over the same years.

Cốc Cốc's own reasons to optimize for its search engine still quote an 11.3% desktop share from February 2022 and more than 574 million queries a month in 2021. StatCounter's yearly desktop figure has stayed below 10% in each year from 2022 to 2025, and in 2026 so far.

What does Cốc Cốc give site owners instead of Search Console?

Cốc Cốc gives site owners a form to submit single URLs and a crawler that reads the Sitemap: line in your robots.txt. Cốc Cốc names its help hub Cốc Cốc Search Console, but its pages describe no site verification, sitemap upload or performance report. Most were last updated on July 15, 2022.

The crawler rules differ from Google's in ways that show up in server logs:

• Language and domain first. Cốc Cốc's indexing page says its robots prioritize websites in Vietnamese or on a .vn domain, and links from sites with many visitors from Vietnam.
• Crawl-delay works. The Cốc Cốc robots.txt guide caps the delay at 10 seconds, so a value of 100 counts as 10. Google's robots.txt specification lists crawl-delay among the fields it does not support.
• Named bots. coccocbot-web is the main robot, with separate image, fast, ads and shopping robots. You can target each one in robots.txt or a noindex meta tag.
• Fake bot check. A real Cốc Cốc robot's IP resolves to a host name ending in .coccoc.com, and that host name resolves back to the same IP.

How do diacritics change Vietnamese keyword research?

Google Keyword Planner cannot tell you which spelling people type. Its historical metrics count searches for "a keyword and its close variants". Google's close variants definition includes accents, in all languages. Entering "cà phê" and "ca phe" can return one shared figure.

The unaccented form throws away information the accented one carries:

The Vietnamese alphabet has 29 letters, according to the MSU course. Seven of them carry their own marks before any tone mark goes on: ă, â, đ, ê, ô, ơ and ư.

Search Console is where the two forms separate. Its Performance report groups the Queries tab by the query users typed, so "ca phe" and "cà phê" appear as two rows, each with its own impressions and clicks, when both reach your site.

Google does not document how its organic ranking treats a query typed without marks, so test it before you plan around it:

1. Search both forms from a Vietnamese location with the interface in Vietnamese.
2. Compare the top ten results. Heavy overlap suggests Google reads them as one query; different pages suggest two.
3. Repeat on coccoc.com/search, which runs its own index.
4. Check your Search Console queries each month for the spelling that earns impressions.

How should Vietnamese URLs and slugs be written?

Google accepts either form in a URL. Its URL structure guidelines tell you to use words in your audience's language "and, if applicable, transliterated words". They also say non-ASCII characters should be percent encoded in links, with gemüse written as gem%C3%BCse.

A Vietnamese slug follows the same pattern. Inside an href, the slug cà-phê becomes c%C3%A0-ph%C3%AA. The accent-free slug ca-phe needs no encoding. Google's guide does not say one ranks better than the other.

The accented choice carries a trap. Unicode can store the same visible letter as one precomposed character or as a base letter plus combining marks, and Unicode Standard Annex #15 defines normal forms so software can treat the two as equal. Their encoded URLs still differ. Precomposed cà-phê is c%C3%A0-ph%C3%AA; decomposed it becomes ca%CC%80-phe%CC%82.

Google treats URLs as case sensitive, the same guide notes, and a byte-level difference produces a different URL string too. Pick one form, normalize slugs to NFC in your CMS, and redirect the others. Google's multilingual site guidance adds one rule for localized URLs: use UTF-8 and escape them when you link.

How does Vietnamese word segmentation affect keywords?

A space in Vietnamese separates syllables, not words. The team behind the RDRsegmenter tool puts it this way in their LREC 2018 paper: "thuế thu nhập cá nhân" is five syllables but a two-word phrase, thuế_thu_nhập (income tax) plus cá_nhân (personal).

The same paper, citing two 2008 studies, says about 85% of Vietnamese word types have at least two syllables, and more than 80% of syllable types are also words by themselves. That overlap stops a machine from splitting text on spaces. Cá, meaning fish, is a word on its own and also half of cá nhân.

For keyword work this changes three habits carried over from English:

• Word-count filters count syllables. Any filter that splits on spaces reads the two-word tax phrase as five words, so a "long-tail" cut at four words removes it.
• Partial matches mislead. A keyword list filtered for "nhân" returns every compound built on that syllable, from cá nhân to nhân viên.
• Segmenters still miss. RDRsegmenter scored an F1 of 97.90% on the Vietnamese treebank, the highest in the paper's comparison table, which still leaves some phrases split in the wrong place.

Which keyword research tools carry Vietnamese data?

Ahrefs holds 743 million keywords for Vietnam, the second-largest index in Southeast Asia after Indonesia's 831 million, on its Big Data page. The tool covers 217 locations in total.

Each tool reaches Vietnamese data in a different way:

Semrush's country list includes Vietnam among more than 140 databases. Its results limit article explains the catch: past the top 10 results, a database outside the original 28 must be connected to your account. Two connections are free.

For Cốc Cốc's own searches, its advertising blog names a keyword planning feature for advertisers on the platform, and suggests the search box's autocomplete as a free source of ideas.

Paid plans on a monthly bill start at $139 on Semrush's pricing page and $129 on Ahrefs' pricing page, with annual billing lowering both.

If I were starting a Vietnamese site on a small budget, I would pull concepts from Keyword Planner and spellings from Search Console before paying for either. Our SEO freelancer rates by country put those tool costs next to the cost of the person running them.

How do you set hreflang for Vietnamese pages?

Use hreflang="vi" for Vietnamese content in any country, or hreflang="vi-VN" for Vietnamese aimed at Vietnam. Google's localized versions guide requires the language code first, in ISO 639-1, with an optional ISO 3166-1 region after it. It warns that a country code alone does not work, so hreflang="vn" gives Google no language.

Hreflang tells Google which pages are versions of each other. It does not tell Google what language a page is in.

"Google uses the visible content of your page to determine its language."

That line comes from Google's multilingual guidance, which also says Google ignores lang attributes for this purpose. Google asks for one language across content and navigation, so a Vietnamese page with an English menu mixes the two. Our guide to SEO and AEO principles for front-end developers covers the markup side.

English pages can reach Vietnamese searchers too. Vietnamese is one of 21 languages into which Google may translate a result's title link and snippet, per its translated results documentation. A notranslate robots meta tag opts a page out.

Which local signals matter for a business in Vietnam?

A .vn domain is the one signal both engines name. Google's multilingual guidance calls country-code domains a strong signal of the intended country. Cốc Cốc's crawler scans .vn sites and Vietnamese-language pages first.

Google's other locale signals, from the same guidance:

• Hreflang annotations in tags, headers or sitemaps.
• Server location, which Google calls not a definitive signal because of CDNs.
• Local addresses and phone numbers, local language and currency, and links from other local sites.
• Signals from a Business Profile, where available.

For map results, Google's Business Profile help ranks local listings on relevance, distance and prominence. It says there is no way to pay for a better local ranking. Our post on local SEO schema and Google Business Profile covers LocalBusiness schema and a complete Business Profile.

Zalo is a messaging app, not a search engine. VNG reported 78.3 million monthly active Zalo users in Vietnam, per DataReportal's Digital 2026 Vietnam report. A Zalo Official Account lets a business publish articles and videos, message customers and carry a verification badge. Neither engine documents it as a ranking signal.

What goes wrong when content is translated for Vietnamese search?

Machine translation at scale can break Google's spam policies. Its scaled content abuse policy lists generating many pages "through automated transformations like synonymizing, translating" where little value reaches users.

The smaller mistakes are more common, and each has a Google rule behind it:

• Side-by-side translations. Google's multilingual guidance asks for one language per page, content and navigation together.
• Template-only translation. Translating the menu and footer while the body stays in English can put the same content in results several times.
• Automatic redirects by language or IP. Google advises against both. Most Google crawls come from the US and send no Accept-Language header, so Googlebot may never see the Vietnamese version.
• Stripped marks in body copy. Text pasted from a tool that drops diacritics reads as ma, ma, ma. Google detects language from visible text, so this is the copy it has to work with.

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Vietnamese SEO: frequently asked questions

Does Bing matter for SEO in Vietnam?

Bing is a minor factor: it took 1.58% of desktop and 0.07% of mobile search referrals in Vietnam in August 2026, per StatCounter.

Where can I find more data on Vietnam's search market?

Our Vietnam digital marketing statistics cover internet, social and e-commerce use, and Southeast Asia SEO statistics compare Vietnam with five neighbours. For agency options, see the top SEO agencies in Vietnam.