Which JavaScript CDNs Work in China

Of the four public JavaScript CDNs covered here, only Google’s fails in the published tests from mainland China. GreatFire reads ajax.googleapis.com as blocked (last tested 22 August 2026), and a 21YunBox probe on Alibaba Cloud (阿里云) in Zhangjiakou got no first byte from Google’s library website on 28 August. jsDelivr answered from the same cloud region and from a Beijing home line. cdnjs and unpkg read as not blocked.

Ask whether a CDN is blocked in China and the reply that holds up is a list of hostnames. Only one of the four takes the page down with it. Every figure below was checked against its source on 11 October 2026.

Is your CDN blocked in China? What the tests show

Every row comes from GreatFire or 21YunBox, with the date each one tested. A 21YunBox census figure is a timed load of the vendor’s own website from their probe. It shows how that company’s own site fares from inside China. The file your page asks for was never part of the test.

From a probe on Alibaba Cloud (阿里云) in cn-zhangjiakou, 280 sites were each requested three times with a 60-second ceiling. The cdnjs website completed 3 of 3 attempts. Google Hosted Libraries gave no response at all. Source: 21YunBox, 280 Sites Measured From Inside China, 28 to 29 August 2026. https://www.21cloudbox.com/websites-blocked-in-china.html

A common shortcut says public CDNs don’t work in China. The same study put that to the test.

21YunBox concludes from its census that the rule “public CDNs don’t work in China” is not supported by its measurements. Source: 21YunBox, 280 Sites Measured From Inside China, 28 to 29 August 2026. https://www.21cloudbox.com/websites-blocked-in-china.html

Google Hosted Libraries stops the page

Google’s documentation gives the jQuery tag in full, pointing at https://ajax.googleapis.com/ajax/libs/jquery/3.7.1/jquery.min.js, and sells the service on its reach.

Google describes Hosted Libraries as “a stable, reliable, high-speed, globally available content distribution network” and gives the jQuery snippet on ajax.googleapis.com. Source: Google for Developers, Hosted Libraries, last updated 9 October 2026. https://developers.google.com/speed/libraries

A plain script tag stops the parser until its file arrives.

“Scripts without async, defer or type="module" attributes, as well as inline scripts without the type="module" attribute, are fetched and executed immediately before the browser continues to parse the page.” Source: MDN Web Docs, the script element, last modified 9 May 2026. https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements/script

From inside the mainland, this one doesn’t arrive. GreatFire’s last conclusive test of the host failed, and 21YunBox’s probe couldn’t even get a first byte out of Google’s library website.

GreatFire reads https://ajax.googleapis.com as blocked: 100% of the last 1 conclusive tests failed in mainland China, last tested 22 August 2026. Source: GreatFire, last tested 22 August 2026. https://en.greatfire.org/https/ajax.googleapis.com

21YunBox tried the page developers read before they copy the tag.

From an Alibaba Cloud (阿里云) cn-zhangjiakou probe on 28 August 2026, the Google Hosted Libraries website returned no first byte in three of three runs, each abandoned at the sixty-second limit. Source: 21YunBox, Google Hosted Libraries in China, reviewed 8 October 2026. https://www.21cloudbox.com/support/google-hosted-libraries.html

The visitor stares at a white page until the browser gives up on the request. Then every script that needs jQuery fails as well: the menu, the slider, the form validation, whatever the theme hung off it. The tag often came in with a theme or a plugin years ago, so the people who run the site today may not know it is there. From an office in Frankfurt or Chicago the same page loads normally. Seen from outside China, nothing looks broken.

jsDelivr answers from both networks, slowly

jsDelivr is the only CDN here with figures from a datacentre and a home line. It completed every request on both.

From an Alibaba Cloud (阿里云) cn-zhangjiakou instance sampled every ten minutes for twelve hours on 28 August 2026, with a 30-second timeout, cdn.jsdelivr.net completed 72 of 72 requests at a median 660ms time to first byte and a 95th percentile of 1,757ms; fonts.googleapis.com completed 72 of 72 at 111ms. From a Beijing China Mobile (中国移动) residential line on 30 August 2026, cdn.jsdelivr.net was requested 36 times with no failures and fonts.googleapis.com 54 times with no answer. Source: 21YunBox, A Chinese Cloud Probe Is Not a Chinese Visitor: The Same Hosts, Opposite Answers, 28 and 30 August 2026. https://www.21cloudbox.com/a-day-of-third-party-requests-from-inside-china.html

From the datacentre on 28 August, Google’s font stylesheet came back in a median 111ms. jsDelivr took about six times as long, and 21YunBox spells out what its slowest requests cost.

“A p95 of 1,757ms against a median of 660ms means one request in twenty takes nearly two seconds.” Source: 21YunBox, A Chinese Cloud Probe Is Not a Chinese Visitor: The Same Hosts, Opposite Answers, 28 and 30 August 2026. https://www.21cloudbox.com/a-day-of-third-party-requests-from-inside-china.html

GreatFire agrees the host is open: not blocked, three of three recent conclusive tests, last tested 8 October 2026. Loaded with async, that tail costs little. Put a jsDelivr file in front of the first paint (a slider plugin’s script in the head, say) and the slow requests hold up the page.

cdnjs and unpkg rest on thinner records

The last two hosts are where the evidence runs thin. Both read as open, yet neither has a published home line test, so that column stays empty for them.

GreatFire reads https://cdnjs.cloudflare.com as not blocked, 1 of 1 recent conclusive tests connected normally, last tested 27 September 2026, and https://unpkg.com as not blocked, 1 of 1, last tested 14 August 2026. Source: GreatFire, last tested 27 September and 14 August 2026. https://en.greatfire.org/https/cdnjs.cloudflare.com and https://en.greatfire.org/https/unpkg.com

cdnjs has one more data point, from the census: its website finished all three loads from the Zhangjiakou probe. unpkg has GreatFire’s single test and nothing more.

The gap matters. A datacentre answer can be the wrong one, and the font stylesheet above shows how wrong: 72 of 72 from the datacentre on 28 August, no answer to any of 54 requests from the Beijing home line two days later.

BootstrapCDN has no dated test of its asset host from either source. It is listed as untested.

Moving the libraries into your own build

Delete the Google Hosted Libraries tag first. Serve jQuery from your own origin, or bundle it into your build, and a request that never returns is gone. Write down the version you copied. The next upgrade should happen because someone chose it. On WordPress the local copy already exists: version 7.1.3 registers jQuery 3.7.1, the same version as Google’s snippet, from wp-includes/js/jquery/. Remove whatever swaps in the Google copy and core’s own file loads instead. 21YunBox gives the same advice.

The census advice: “measure the host you actually depend on, or bundle the library into your own build and remove the question.” Source: 21YunBox, 280 Sites Measured From Inside China, 28 to 29 August 2026. https://www.21cloudbox.com/websites-blocked-in-china.html

Our guide to the WordPress plugins that break in China shows how these tags get into a site. For hosts beyond the library CDNs, the guide to what the Great Firewall blocks has the wider dependency table. Not sure which library hosts your pages call? The China Site Scanner checks for them. The build work is what our Technical Integration service does.

Common questions about CDNs in China

Is cdnjs blocked in China?

No dated test says so. GreatFire read cdnjs.cloudflare.com as not blocked on 27 September 2026, and 21YunBox’s census loaded the cdnjs website 3 of 3 times from an Alibaba Cloud probe on 28 to 29 August. Neither GreatFire nor 21YunBox has published a home line test of cdnjs, so what a Beijing household sees is unknown.

Is jsDelivr blocked in China?

No. In 21YunBox’s study it completed 72 of 72 requests from an Alibaba Cloud datacentre in Zhangjiakou on 28 August 2026 and 36 of 36 from a Beijing China Mobile home line on 30 August. It’s slow, though: a 660ms median and a 1,757ms 95th percentile from that datacentre.

Does unpkg work in China?

GreatFire reads it as not blocked. Its one recent conclusive test of unpkg.com, on 14 August 2026, connected normally. Neither GreatFire nor 21YunBox currently publishes a datacentre timing or a home line test of it. Treat unpkg as reachable but unmeasured, and bundle anything your first paint depends on.

Why does jQuery from Google freeze the whole page?

A script tag without async or defer stops the browser parsing until the file arrives. GreatFire reads ajax.googleapis.com as blocked, so from the mainland the file never arrives. The page waits for a timeout, and every script that depends on jQuery fails after it.

Do I need a China CDN to fix this?

Bundling fixes this one without any CDN. These are files somebody chose to fetch from another company’s server every time the page loads. Put them in your own build and the request is gone. Where your own site is served from, and whether it holds an ICP filing (ICP备案), is a separate question about your own pages.