They used Google Photos.
Not free, but gave free trails to police across the world.
Be careful of what you post online! Delete any photos you posted online and ask others who posted a pic of you to remove it if possible (this may raise suspicion btw).
Good advice that apparently can’t be reiterated enough. If raising suspicion is a concern, accompany requests with explanation and links to the above articles.
It’s okay to politely refuse to be photographed in social settings. The less you are photographed, the less data about you that will end up online and in databases. Exercising this right also tells people around you that privacy is okay.
Something I can’t recommend to everyone is it helps to cut ties with psychopaths who think doxxing everyone around them is a virtue. Instead, hang out with people who respect privacy or at least respect your privacy.
If you need to share a photo that depicts people, perform effective redaction of their faces and other identifying features. Some software like ObscuraCam (stale?) are specifically designed for that, but I just use standard image editing software. Just make sure the redacted information is actually overwritten and not merely covered by a removable layer or made possible to undo. Some blurring algorithms can be reversed (deconvoluted) to some degree, so overwriting with a solid color or emoji is safest.
I never was the type to take selfies or go to parties where a group photo would be taken and I’m so glad for this.
Today, I always wear a N95 indoors due to perfume sensitivities.
Sometimes, it pays to be anti-social and have a health problem, lol.
Face recognition works with majority of masks too.
Thanks for post. I wonder if my closed facebook account photos i downloaded are somewhere being used. I’d have to image search every single one. But then im uploading it to search for it so 
Be careful of what you post online! Delete any photos you posted online and ask others who posted a pic of you to remove it if possible (this may raise suspicion btw).
I think we should add the clarification that if you are someone who travels through international borders (after immigration), deleting photos off of social media is probably not enough nor it is possible when you work in a public setting, i.e. academia.
EDRi cites technology announced in 2021.
As facial recognition technology must adapt to the “New Normal,” NEC developed the new algorithm which specifically focuses on the (periocular) area around the individual’s eyes for use in a broad range of applications from smart phones to workplaces.
The engine performs mask detection, and based on the result selects which algorithm to use for biometric face matching.
NEC’s technology focuses on around and between the eyes if a mask is detected, which may include the eyebrows and forehead. Wearing eyeglasses, a visor, a hat, a balaclava, etc, may help defeat the technology.
The engine was found more than 99.9 percent accurate in internal 1:1 verification tests with masks of various colors and patterns.
The technology was highly successful at one-to-one verification when put through laboratory testing, but how well it works in production to identify (not just verify) faces may be a very different story. Still, I don’t deny the technology is capable of identifying some people’s faces with certain degrees of confidence.
Similarly, according to the same article, the Face Recognition Company (FRC) developed a facial recognition technology they claim has a negligible performance difference for masked and unmasked targets, anticipating the need for such technology before the COVID-19 pandemic.
Generally speaking, I think the efficacy of facial recognition technology would depend highly on the specifics of the recognition technology, training data, environment (for example, lighting and camera position), image quality, target person and their mask (or other coverings).
Assuming surveillance technology developers will continually improve their products, countering them will be an arms race that people will eventually lose to. Too much identifying information (biometrics or otherwise) is remotely perceptible by cameras and other sensors. However, not letting the perfect be the enemy of the good, the more biometrics someone conceals and the less often they are exposed to sensors, generally the better off they will be against this kind of surveillance.
Corporate/government surveillance systems are not the only threats to privacy in the physical world. There’s literally billions of cameras carried around by people and attached to vehicles and houses.
That article is very unconvincing.
They test a variety of masks but have no idea how most of the facial recognition systems work. “we don’t know” was stated many times throughout the article.
I’ll continue to wear a mask in public to keep my perfume exposure down.
If it foils FR, great. I’ll take that as a bonus.