Dan McDevitt is grants and communications manager at GreatFire.org, a group focused on monitoring and challenging Chinese internet censorship.
When Hong Kong's national security law went into effect last June, many residents scrubbed their social media accounts of controversial content and switched communications to more private, encrypted alternatives.
Use of virtual private networks (VPNs) increased, too, as did self-censorship -- a byproduct of concern about the vague, broad powers entrusted to the authorities under the Beijing-imposed law.
For about half a year, this was largely the extent of the security law's internet impact. By some measures, Hong Kong's internet remained as free as it had been prior to the security law's passage.
But recent events have made plain the Chinese government's intention to transform Hong Kong's digital spaces just as it has the city's offline environment and, last week, its electoral system.
In January, Hong Kong authorities used the security law as grounds for blocking a website for the first time, compelling mobile providers to disrupt access to HKChronicles, which compiled information on anti-government protests and personal data on police and their supporters.
Around the same time, the company in charge of approving Hong Kong website domain registrations announced it would reject websites if it believed they might encourage illegal acts or provide false information.
Two weeks later, the government unveiled a plan to require buyers of mobile phone SIM cards to show personal identification. Readily available prepaid SIM cards have, until now, provided a key way for activists to protect their identities during protests, granting Hong Kongers an anonymous way to communicate and organize.
While the government solicited public comment on the plan for a month, there was no reason to think that concerns or criticisms would be taken seriously.
Once the plan is instituted, self-censorship may spread beyond public websites to include private communications, closing yet another space where civil society has operated with some modicum of safety. Anyone caught faking their registration details could be jailed for up to 14 years.
Since China made real-name registration mandatory for SIM card purchases in the mainland in 2010, Beijing has improved enforcement with tactics such as requiring facial scans to catch buyers using fake IDs.
Such lessons could make this export from Beijing's repressive surveillance playbook to Hong Kong alarmingly effective.
Over the past decade, Hong Kong's internet has not developed with control in mind as China's has. This difference will create technical challenges that make exporting the Great Firewall wholesale to Hong Kong exceedingly difficult for Beijing.
But while a simple drag-and-drop approach of directly applying policies from the mainland won't work, a more piecemeal process could. Beijing has no shortage of censorship and surveillance tools at its disposal and some may even be more effective in Hong Kong than in the mainland.
For instance, Apple has proved to be willingly complicit in Chinese government censorship, removing hundreds of VPN apps from its mainland app store at the authorities' request.
If China were to start making similar demands on Apple's Hong Kong app store, the impact would be significant as the company's devices are more widely used in the city than almost anywhere else in the world, with nearly half of residents carrying an iPhone.
Beijing could also impose restrictions on the functionality of VPNs by compelling operators to limit the sites they are able to connect to, as it has done in China. Alternatively, authorities could simply disrupt the technical operability of such tools, rendering them frustratingly slow or ineffective.
On a content level, China could request any Hong Kong website to moderate or remove material found objectionable, though the human labor that makes this sort of mandatory private cooperation possible in the mainland would take significant time to organize.
While it may be harder to censor an internet that has long been free, all available indicators suggest that the trend is likely to continue toward more online controls.
For Big Tech companies operating in Hong Kong, it is imperative that they act in accordance with their stated values of human rights and free expression by resisting any orders, legal or otherwise, that violate such principles.
Soon after the national security law's passage, Google, Microsoft, Twitter, Telegram and Facebook each said that they would "suspend" responding to requests for user data from the Hong Kong government.
But it is unclear whether these companies have already reverted to business as usual and are cooperating with such requests or whether they may quietly do so later. For the sake of their Hong Kong users' safety, tech companies need to be as transparent as possible and provide clear updates on their operations in Hong Kong.
Contrary to the predictions of former U.S. President Bill Clinton, the Chinese government has effectively "nailed Jell-O to the wall" with its effective controls over online information flows, so we should not be surprised that they would try to do it again in Hong Kong.
But we can also be sure that just as in China, dissident groups and voices will continue to operate, even at great personal risk. At this critical moment, it is important that the world support these voices and not cast a blind eye to what is happening in Hong Kong, online and off.