My blog has both Chinese and English versions. Search engines use the hreflang tag to understand “which page is Chinese, which is English.” I found out the hard way that an ambiguous declaration can quietly hurt search rankings.

How Search Engines Know There Are Two Versions

My site has Chinese and English copies. How does a search engine know they’re two languages of the same content?

That’s what hreflang is for. It looks like this:

<link rel="alternate" hreflang="en" href="https://example.com/en/page/">
<link rel="alternate" hreflang="zh" href="https://example.com/zh/page/">

The Chinese page declares where the English version is, and the English page declares where the Chinese version is. They point to each other, so the search engine knows these are two language versions of one piece of content — not duplicate content fighting each other.

The Most Common Trap: Region Codes

Many sites take a shortcut and declare “Chinese (mainland China)” and “English (US).”

<hreflang="zh-CN">   <!-- Chinese (mainland China) -->
<hreflang="en-US">   <!-- English (US) -->

Sounds fine, but here’s the problem: a Chinese speaker in Singapore, a user in Taiwan, a developer in the UK — none of them fit “mainland China” or “the US.” When they search, the search engine doesn’t know which version to show. The two versions fight over rankings in those regions, neither ranks stably, and the traffic they’d bring is lost.

So when content isn’t region-specific, plain language codes are the way to go:

<hreflang="zh">
<hreflang="en">

Region codes only make sense when content is deliberately differentiated by country, like separate copy for the US and the UK.

The Easy-to-Miss One: The Fallback

When a user’s language matches none of the site’s languages — say, an Arabic speaker — which version should they see? That’s what x-default handles.

One detail is worth noting: the fallback answer should be consistent across the whole site. If the Chinese pages say “fall back to Chinese” and the English pages say “fall back to English,” the search engine is left guessing. Point consistently at one version, and the behavior stays stable.

Easy to Forget

hreflang is the kind of thing that gets configured once and then forgotten. And precisely because it’s a set-once thing, many sites keep running with an ambiguous declaration without anyone realizing it.

Now, whenever I notice rankings mysteriously unstable in certain regions, I check the language declaration first. Maybe the problem lives there.

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