Public Wi-Fi and Anonymity

Public Wi-Fi may be available in cafes, stations, hotels, libraries, event venues, and similar places.

When you use public Wi-Fi, it may look as if you are accessing the internet from that place's network rather than from your home connection's IP address. For that reason, some people think that using public Wi-Fi makes them anonymous.

But that is not accurate.

With public Wi-Fi, the source IP address visible to outside services may change. At the same time, other clues may remain, such as the Wi-Fi operator, other users on the same network, the destination website, surveillance cameras, login state, and device information.

This article organizes what changes and what does not change when using public Wi-Fi.

What public Wi-Fi is

Public Wi-Fi is a Wi-Fi network provided for an unspecified number of people or for facility users.

For example, it may be provided in places such as the following.

• Cafes
• Stations
• Airports
• Hotels
• Libraries
• Commercial facilities
• Event venues
• Guest Wi-Fi at schools or workplaces

When you connect to public Wi-Fi, your device reaches the internet through that facility's or operator's network. For that reason, the IP address visible to the destination website may be the outside IP address of the public Wi-Fi side rather than your home connection.

However, using public Wi-Fi is not the same as anonymization.

What changes with public Wi-Fi

When you use public Wi-Fi, part of the communication route changes.

With home Wi-Fi, the device goes outside through the home router and contracted connection. With public Wi-Fi, it goes outside through the facility's or operator's access point, router, and connection.

In other words, using public Wi-Fi may change the network visible to the destination.

But that alone does not make the user unknown.

Information that may be visible on public Wi-Fi

On public Wi-Fi, connection records may remain on the network operator side.

Which information is recorded depends on the facility, operator, equipment, authentication method, and retention policy. However, when thinking about anonymity, you need to be aware that information like the following may be visible.

When HTTPS is used, much of the communication content is protected. However, the fact of connection, traffic volume, time, and information about the destination do not disappear.

Also watch other users on the same network

On public Wi-Fi, many people may use the same network.

Because HTTPS is used for much modern web communication, a third party on the same Wi-Fi cannot necessarily read web page body text or passwords directly. However, public Wi-Fi is an environment that is harder to trust than a home network.

For example, there are risks such as the following.

• Unencrypted communication may be eavesdropped on
• You may connect to a fake Wi-Fi access point
• You may enter information into a login page shown when connecting
• Device sharing settings or old vulnerabilities may be targeted
• DNS or communication-route settings may be forced into an unintended form

When using public Wi-Fi, it is important to confirm HTTPS, update the OS and browser, and avoid carelessly opening sharing settings.

However, these are security measures. They do not establish anonymity by themselves.

Surveillance cameras and location records also become clues

With public Wi-Fi, you cannot look only at information on the network.

Places with public Wi-Fi may also have other records, such as surveillance cameras, entry and exit records, payment records, transit-card use histories, membership logins, and device location history.

For example, if access from public Wi-Fi occurs at a certain time, there is also a record of entering that place at the same time, and surveillance camera footage shows the person, those clues may connect with information outside the network.

For anonymity, you need to consider not only communication logs but also records left in physical places.

Even if the IP address changes on public Wi-Fi, anonymity weakens if place and time clues remain.

Login state and cookies remain as they are

Using public Wi-Fi does not automatically erase browser cookies or login state.

If you access the same service with the same browser, the website side may treat you as the same account or the same browser.

For example, if you access a social media account that was logged in at home from public Wi-Fi using the same browser, the source IP address may change. However, to the service side, it appears as the same account.

When thinking about anonymity, which browser, which account, which cookies, and which device you use can matter more than whether you use public Wi-Fi.

Public Wi-Fi is not anonymization technology

Public Wi-Fi is an environment that changes part of the communication route. It is not anonymization technology itself.

Using public Wi-Fi may prevent the destination from seeing your home connection's IP address. However, connection records may remain with the public Wi-Fi operator. The destination website may also see cookies, login state, User-Agent, access time, and similar information.

It is dangerous to think, "It is not my home IP, so I am anonymous." Anonymity is not determined by IP address alone.

Basic thinking when using public Wi-Fi

When using public Wi-Fi, first separate the purpose.

Do you simply want to browse the web safely? Do you not want the destination to see your home connection's IP address? Do you want to make your destinations harder for the public Wi-Fi operator to see? Do you want to avoid connecting an account with an action?

The necessary measures change depending on the purpose.

Public Wi-Fi is convenient, but it does not guarantee anonymity. Even when using a VPN or Tor, who can see things and who you must trust change; search terms, login state, cookies, and records on the destination service side do not disappear. You need to separate your purpose from who you want to hide what from.

Summary

When you use public Wi-Fi, the IP address visible to the destination may become the public Wi-Fi side's IP address rather than your home connection.

However, public Wi-Fi is not anonymization technology. Other clues may remain, such as Wi-Fi operator logs, DNS queries, traffic volume, connection time, surveillance cameras, payment records, cookies, login state, and browser information.

HTTPS is important for protecting communication content, but it is not a mechanism for making public Wi-Fi users anonymous.

When thinking about anonymity, do not look only at whether your home IP is visible. Separately consider what the public Wi-Fi operator can see, what reaches the destination website, and whether it connects with on-site records.

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