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This article was co-authored by David Cohen and Chris Udemans.

As China goes back to work after weeks of epidemic lockdown, it’s betting on high-tech QR code quarantines to keep the virus from spreading.

In the eastern Chinese city of Hangzhou, scanning a QR code at a checkpoint with Alipay has become a routine part of daily life. It’s essentially a health passport for the city. A mini-app embedded in Alipay or WeChat rates people as red, yellow, or green risks. To enter an apartment complex or a market, residents must scan a QR code at a manned checkpoint, letting the system know where they are and producing a one-time color code pass to show the guard.

Hangzhou, the capital of Zhejiang province, became the first to adopt the QR code system on Feb. 11, although lockdown continued for most residents until Feb. 15. Alipay announced on Feb. 16 that it was ramping up development support for a national health code system that assesses individuals for self-quarantine based on basic health information and travel history, which it is preparing to launch this week under the guidance of the State Council, China’s cabinet.

Read more: How China built its health surveillance system

In a statement provided after publication of this article, Alibaba said that ratings are provided by government, not the company, using Alipay as a platform. Referring to widespread references in Chinese media to an “Alipay health code,” the company said: “It is marketing language used for promoting usage. In reality, these are not Alipay-issued health codes, but rather are issued by governments.”

By Feb. 20, Alipay boasted that platforms it had helped develop were already in use in over 100 cities, including all cities in Zhejiang, Sichuan, and Hainan, as well as Chongqing.

According to our observations, there is no place that enforces the health passport system as rigorously as in Zhejiang.

But national implementation doesn’t mean a unified national system—instead, each participating city is launching a local version of the system, creating a fragmented landscape resembling local social credit system pilots. Some have versions of Alipay’s system, some have local apps—and others have both. While online tracking ended Hangzhou’s total lockdown, many other cities have not revised quarantine rules to reflect new online systems.

How QR code systems work

As of Feb. 25, sources on the ground described very limited implementation outside Alipay’s home province of Zhejiang, ranging from paper-based lockdown in Shanghai to laxly enforced digital checkpoints in Shenzhen. Talking to locals in cities that have adopted health passport systems, TechNode saw its limits: the app alone does nothing without human-based enforcement and public compliance, and few cities outside Zhejiang have overcome these human challenges.

The system shows both how much is possible with high-tech surveillance—and how much human input is required to make such systems work.

To register, individuals provide their name, ID number, phone number. The health-rating platform, asks a series of questions, including physical health condition and whether the individual has traveled to virus-hit areas or has come into contact with infected cases, to produce an initial rating. These ratings are reported to change, likely informed by where the user has checked in and new reports of infections.

According to Hangzhou rules, residents with a green code are allowed to move around the city freely. Yellow means a seven-day quarantine is required, and red requires a 14-day quarantine. Some versions adopt a slightly different color-coding system, but the general idea is the same—to track mobility and regulate it based on risk assessments. Though the questionnaires record self-reported information, public data is used for verification purposes.

Internet users have questioned the way the system analyzes health and travel data. In numerous accounts on microblogging platform Weibo, netizens said people living in the same household were given different color codes even though they had been isolated together for weeks.

Others have expressed frustration with unpredictability, saying they were initially given a green code only to have it change to red after a few days. The colors are dynamic, and some people taking what they believe to be adequate measures to protect themselves while outdoors have had their mobility limited after their code changed color.

While Alipay’s version is associated with a State Council project, local governments are not required to adopt it. WeChat operator Tencent is working with the State Information Center to develop similar QR code-passed health passports.

Tencent’s version, called “Tencent Healthcare Code,” is already available in provinces including Guangdong, Sichuan, and Yunnan.

While the system has the potential to bring a semblance of normal life back to places that have been locked down for weeks due to the outbreak, to create a surveillance system capable of tracking 1.4 billion people everywhere they go comes at great challenges and costs.

To enter market, scan QR code

Uny Cao, a resident of Hangzhou, says that he scans twice a day—once when he goes to the vegetable market, and once when he returns home. Getting on the subway, riding a bus, or going to a park would mean more scans, so he’s chosen to limit these behaviors. Many also avoid borrowing share bikes, reasoning that the apps may share data with the Health Code:

“A few days ago, they found a new case in City North. Rumor spread that if you have rented a shared bike in that region, your code might get a downgrade,” he said. “So for those few days, I avoided renting shared bikes, in case they discover a new patient in my area.”

According to our observations, there is no place that enforces the health passport system as rigorously as in Zhejiang.

Regular scans both track and shape behavior. Sources told TechNode that citizens are required to show their code to be scanned when entering supermarkets and residential areas as well as getting on the subway and buses.

For Hangzhou residents, the inconveniences are a small price for something like normal life—for the ten days before the app launched, the city was forced to stay indoors except for short trips to buy food every other day. Since the code system came in, residents have been allowed to leave their homes and even to drive to other cities.

Even here, enthusiasm has its limits: While apartment buildings and food markets appear to be rigorously enforcing the rules, TechNode correspondents have walked into banks past napping checkpoint guards. Restaurants and smaller shops are starting to re-open without check-in systems.

The Hangzhou version of the mini-app, which the national version will reportedly be based on, allows non-Hangzhou residents and foreigners to register. Other places such as Shanghai and Shenzhen’s platform only allows residents to apply for a pass.

The Hangzhou health passport works for long-distance travel. When a TechNode correspondent traveled from Shanghai to Hangzhou, train station staff checked travelers’ health codes and wrote down their ID numbers. Travelers who had applied for codes outside of Hangzhou had no problems entering the city.

Mileage may vary

Beyond Hangzhou, enforcement can be more lax. In Jinhua, a city in Zhejiang 180 kilometers south of Hangzhou, a 25-year-old city resident told TechNode that she only needs to use the system when taking public transport. Her local supermarkets and residential community do not check the color of her QR code when she leaves her apartment. The system is enforced more stringently for out-of-towners, she said.

In a rural area, quarantine guards suggested a TechNode correspondent write down an ID number on a piece of paper to save time registering with a local version of the color codes mini-app.

But other cities can enforce non-app limits far more strictly, suggesting that they do not fully trust the app: A resident in the eastern Chinese city of Ningbo says there are checkpoints set up at community complexes and supermarkets. People are being asked to show, but not scan, their QR code at public places. On top of enforcing the new health code system at the community level, the previous lockdown rules still apply, the Ningbo resident said. In her apartment compound, residents are required to show the QR code at the entrance of the complex and still adhere to the rule that every household can only send one person out every two days.

The source also said her relative purposely left out the fact that he just came back from Wuhan when filling out the questionnaire. The police called days later and ask why he didn’t report it. They found the license plate under his name had been in Wuhan recently.

For people that have returned to their work, they have to show the QR code when leaving the apartment complex and also show a document from their employer that permits them to return to work.

Active but unused

TechNode sources described health passport systems that were implemented either spottily or not at all. In some places, including Shanghai, Beijing, and central China’s Hubei, the worst-hit province in the country, apps were superseded by strict offline measures; in others, such as Guangdong, quarantine appears to be lax.

More than a week after launching a track-everything health code system, Shanghai is still very much relying on paper records to enforce a 14-day quarantine on all new arrivals. Shanghai launched health passports as a new feature within its pre-existing “Health Cloud” mini-app on Feb. 17, accessible on Alipay and WeChat. But TechNode correspondents could not find a place to scan the app inside the city, finding checkpoints at office buildings and apartment complexes relying on paper records and paper cards or stickers to identify approved residents or workers.

In Shenzhen, the headquarter of internet giant Tencent, sources say that the health code system has been mostly ignored as the city hurries to get back to work.

Henk Werner, head of Shenzhen-based hardware incubator Trouble Maker, told TechNode that he and his friends had not bothered to register for the local version unless they wanted to take the subway. Residents are being asked to show QR codes at places like the parking lot of an apartment complex, but found it possible to bypass the checkpoint. Another source in Shenzhen says she hasn’t bothered to register—and that she’s going to work by taxi every day with a paper pass.

The central city of Xi’an has used a more limited pass system that requires scan check-ins but does not display a color code for about a week. Graduate student Liu Weiqi and TechNode editor Wang Boyuan both described checkpoints at the entrances to apartment compounds, but saw mixed use of the app. While Wang saw people using the app to enter his apartment compound, Liu made a trip to the market by bus on Feb. 25, and found that in practice he was registered on paper records everywhere but the market. On Feb. 25, the city announced that it is adopting a version of Alipay’s color code-based pass app.

A source in Chengdu said even though the city implemented a health passport on Feb. 21, it’s not enforced. Residents can go out without being asked to show the code. She said it’s probably because the area she lives in is mostly locals rather than out-of-towners, who are seen as being a higher risk.

At the epicenter of the outbreak, attempts to roll out the health check system have also had limited effect, simply because no one is going out to be checked. Earlier this week Wuhan, the city at the epicenter of the Covid-19 outbreak, launched a Tencent version of the health passport. The local government now recommends residents who need to leave their apartment complex for valid reasons to apply for the pass.

Wu Chuan, a 26-year-old resident of Yichang, a city in Hubei that is approximately a four-hour drive from Wuhan, told TechNode he hasn’t stepped out of his home for close to a month and wasn’t aware of any health passport platform in Hubei.

The city has a strictly enforced health-reporting system that requires citizens to fill out an application if they plan to leave the community complex. Without official approval, they’re forbidden to do so. Wu said the health passport system does not seem to have much use in his city because, unlike Hangzhou and other metropoles that actually allow people out and go about their usual activities, it is still under lockdown.

Suizhou, a city 180 kilometers northeast of Wuhan, has also begun implementing a health passport system. People with green codes will need to have their temperatures checked before being allowed through checkpoints. Those with yellow and red codes will not be permitted to pass. The system is not yet mandatory and a resident of the city told TechNode that she is still not allowed to leave her residential community.

Big data, huge payroll

It is unclear whether the implementation will improve after the launch of the national version of the health code this week. Although it is a standardized system across the country, according to Alipay, local governments have the liberty to decide whether they want to adopt the version of not.

In order for the system to work, cities need to deploy checkpoints on highways and roads, on public transportation, and apartment complexes—which requires tremendous manpower to operate. Then they need to supervise these guards closely enough to make sure they do the work.

Hangzhou under the watchful eye of an app shows us what an extreme version of mass surveillance might look like. But it also shows how far we are from that world—it takes a lot more than the click of a button to know where people are.

This article was edited Feb. 26 to include comment from Alibaba.