Frequently Asked Questions

Who operates uDomainFlag / Who are you?

Hello! I am Thomas Bella and uDomainFlag was build by me as teenager as a project to learn more about browsers, writing backends and getting deeper into programming.
You can read more about me, my hobbies, photographs and other projects on my portfolio at

How many users does uDomainFlag have?

As of September 2021, uDomainFlag is used on Google Chrome by about 6000 users, on Microsoft Edge by about 2000 users and on Mozilla Firefox about 20 users.

Are you selling my data?

No! I am not selling any data and will never do that.
I build uDomainFlag to be a tool to provide more security and to provide deeper insight of websites and services I visit. Selling data goes against the idea of offering a safe and privacy-friendly tool.

Do you sell uDomainFlag?

No! I am not selling uDomainFlag. I am not planning to sell it and I will not integrate advertisement/code/trackers into the extension.
Please stop contacting me to integrate your code/tracker/whatever into my extension. I will not do that and your email will go straight into my junk folder.

How is the project financed?

uDomainFlag was created by me to learn new technologies and I am still learning from it. It was always a hobby and is still one.
The project costs money and is very time-consuming, but the learning effect from it is far more valuable to me than any expenditure.

How can I support uDomainFlag/you?

Nice you ask! You can support the project by providing ideas, helping translate the extensions or even add functionality. uDomainFlag is Open Source and available on GitHub.
Another way to support me is by buying me a coffee which keeps me awake and motivates me even further to continue developing uDomainFlag.

Why isn't the server open sourced? (dfdata)

I am using some private APIs to crawl data like ASN mappings, geolocation data and correction data. A previous version was open sourced and massively abused which resulted into problems with my previous provider.
Until everything is fixed and stable enough, the server dfdata isn't available.

Where do I get support?

For feature requests or issues please use the Issues section on GitHub and for everything else the Discussions section on GitHub.

What data do you track / is my data secure?

uDomainFlag and any used component does not track any data from you. There are no user profiles generated and there isn't any linking between user, requester, visited domains etc.
To improve uDomainFlag, errors within the program are tracked and transmitted to me. You can disable the transmission of this data within the uDomainFlag settings -> disable error reporting. (If you are syncing settings, error reporting will be disabled on all your devices)

What data can you see about me / what data are you processing?

When you visit a website, uDomainFlag transmits the visited domain (e.g. to the uDomainFlag upstream server dfdata at
This is needed determine which IP the DomainFlag server sees from the domain and to return additional information like server location, hostnames and ASN.
uDomainFlag does not transmit any unique identifier which would allow me to identify you.
You can find more details on How it works and in the Privacy Policy.

Can I make a data request according to GDPR?

Yes you can, but I can only provide an empty dataset to you because there is no tracking and I have no way to identify you or your requests on the dfdata server.

Can I use a on-premises / self hosted variant?

Please have a look on the Enterprise page.

Is the data transferred securely?

Yes! I am a security enthusiast and configured uDomainFlag and the upstream server dfdata to be as secure as possible.
uDomainFlag can only communicate over an encrypted HTTPS based channel, validated by your browser and operating system. The upstream server dfdata only allows secure protocols (TLSv1.2 & TLSv1.3) and secure ciphers (AES-GCM & CHACHA20-POLY1305).

My question wasn't answered

If you have a question regarding uDomainFlag, please use GitHub issues or discussions. For everything else, please contact me by mail at